Timber Design

 

De c e m b e r 2 0 0 7

Manual for the design o imbe eo rd be uilding uild ucttur ure es tof tEimb uroc 5 ing struc

Th e In sti titu tu ti tio o n o f Str tru u c tu ra l En g in e e rs TRADA

 

Acknowledgement is given to the following for their support in the production of this  Manual: British Woodworking Woodworking Federation Canada Wood UK James Donaldson & Sons Ltd MiTek Industries Sinclair Knight Merz TrusJoist.

 

Th e In sti titu tu ti tio o n o f Str Stru u c tu ra l En g in e e rs TRADA

Ma nu a l fo r t he d e sig n o f tim ti m b e r b u ild in g str tru u c tur turee s t o Eu ro ro c o d e 5

De c e m b e r 2 0 0 7

timb mb e r b ui uilld ing str struc tur turee s to Eur Euroc oc od e 5 IStruc ructE tE/ TRADA  Ma nua l for the d e sig n of ti

 

i

C ons nsttit itut utio ion n of Task Gr G roup

R J L Ha rr rriis BSc CEng FIStructE FICE AIWSc  (Chairman) R Ha irsta n s  BEng PhD I Ja ne s CEng MIStructE A C La La w re re n c e MA(Cantab) CEng MIStructE MICE J P Ma rc ro ft BSc CEng MICE M W Mil Miln e r MSc BSc CEng MIStructE MICE BSc(Eng) CEng MIStructE P J Ste Ste e rMSc DIC Civil Eng D Tru Tru ji jill llo o

C onsul onsultant tant and tec hnic hnical al wri writer  ter  A V P a g e BSc(Eng) BD AIWSc  Sec re reta tary ry to the Ta sk G roup B H G C re sswe ll Rio l BEng  A c kno w le d g e me nts The Institution of Structural Engineers acknowledges the input and support from TRADA’s service provider, TRADA Technology, in the development of this Manual. Chiltern House, Stocking Lane, Hughenden Valley, High Wycombe, Bucks HP14 4ND, UK  T: +44 (0) 1494 569600, W: www.trada.co.uk  Permission to reproduce extracts from BS EN 1995-1-1:2004 is granted by BSI. British Standards can be obtained in PDF format from the BSI online shop: www.bsi-global.com/en/ www .bsi-global.com/en/shop shop or by contacting BSI Customer Services for hard copies, T: +44 (0) 20 8996 9001, E: [email protected] Published by The Institution of Structural Engineers, International HQ, 11 Upper Belgrave Street, London SW1X 8BH, UK  ISBN 978 0 901297 44 0 Front cover: Sheffield Winter Garden, Pringle Richards Sharratt. Shortlisted in the Wood Awards 2003. © 2007 The Institution of Structural Engineers and TRADA Technology Ltd  The Institution of Structural Engineers and the members who served on the Task Group which produced this Manual  (i.e. both the printed document and the contents of the accompanying CD) have endeavoured to ensure the accuracy of its contents. However, the guidance and recommendations given in the  Manual should always be reviewed by those using it in the light of the facts of their particular case and specialist advice obtained as necessary. No liability for negligence or otherwise in relation to this  Manual and its contents is accepted by the Institution, the members of the Task Group, their servants or agents. Any person using this  Manual  should   should pay particular attention to the provisions of this Condition.  No part of this Manual may be reproduced, stored in a retrieval system or transmitted in any form or by any means without prior permission of the copyright owners.

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tim m b e r b ui uilld ing struc struc tur turee s to Eur Euroc oc od e 5 IStruc uctE tE/ TRADA  Ma nua l fo r the d e sig n of ti

 

ontent ents s C ont Ta b le s

xiii xi

G lo ss ssaa ry  No t a tio n Fo re w o rd 1

Intr ntro o d uc ti tio on 1.1 1.2 1. 2

1 .3 .3

1.4 1.4 1.5

1.6 1. 6

2

xvi x viii xxv xxix 1

Aim s o f the  M Aim  Ma a nua nuall  The Eur uro o c o d e sys yste te m 1.2. 1. 2.1 1 Orig Ori g in a nd p ur urp p o se

1 1 1

1.2.2 List o f Euroc o d e s 1.2.3 1.2. 3 Priinc ip le s a nd App lic a ti Pr tio o n Rul ulee s 1.2. 1. 2.4 4 Na ti tio o na l Anne xe s 1.2. 1. 2.5 5 Non c on tr traa d ic tor tory y c om p le m e nta ry inf nforma orma ti tion on 1.2. 1. 2.6 6 Eur uroc oc od e d e sig n b a sis  Ma a nua l  Sc o p e o f t h e  M 1.3. 1. 3.1 1 Na ti tion on a l sc op e 1.3. 1. 3.2 2 Str truc uc tur turee s c o ve re d 1.3. 1. 3.3 3 Priinc ip a l sub je c ts c o ve re d Pr 1.3. 1. 3.4 4 Sub je c ts no t c ove re d 1.3. 1. 3.5 5 Add iti tio o na l inf nfo o rm a ti tio o n c o nta ine d in the CD 1.3. 1. 3.6 6 So ur urcc e s o f a d d iti tio o na l inf nfo o rm a ti tio on  Ma a nua l  Co nte nts of the  M De fi finiti nitio o ns 1.5.1 1.5. 1 Te c hn ic a l te rm s 1.5. 1. 5.2 2 Axiis no m e nc la tur Ax turee Nota ti tio on

1 2 2 2 2 3 3 3 3 3 4 4 4 4 4 5 5

G e ne ra l p rinc ip le s

6

2.1

Ba si siss o f d e si sig gn 2.1.1 2.1. 1 Ba si sicc re q ui uirre m e nts 2.1. 2. 1.2 2 De sig n c od e s 2.1. 2. 1.3 3 Str truc uc tur turaa l m a te ria ls c o m p lia nc e 2.2 Re sp o nsi nsib b ility fo r d e si sig gn 2.3 2. 3 Bui uilld ing use a nd lo c a ti tio on 2.4 De si sig g n life 2.5 De si sig g n si situa tua ti tio o ns 2.6 Sta b ility 2.7 2. 7 Co nstr nstruc uc ti tio on 2 .8 .8 Mo v e m e n t 2.8. 2. 8.1 1 Moisstur Moi turee m o ve m e nt 2.8. 2. 8.2 2 The rma l mo ve m e nt 2.8. 2. 8.3 3 Difffe re nti Di ntiaa l m o ve m e nt 2.8.4 2.8. 4 Move m e nt jo ints 2.9 2. 9 Cree e p Cr 2.10 2. 10 Rob us ustne tne ss a nd d isp rop ort ortiion a te c ol ollla p se 2.10.1 2.10 .1 Ro b ust c o nstr nstruc uc ti tio on 2.10 2. 10.2 .2 Ac c id e nta l a c ti tion on s

6 6 6 7 7 8 8 8 8 8 9 9 9 10 10 10 10 10 10

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2.11 2.11 2.12 2. 12 2.13 2 .1 .1 4 2.15 2.1 5

Fire re si sista sta nc e Ac o usti usticc , the rm a l a nd a ir ti tig g htne ss re q ui uirre m e nts Dura b ility Ma in t e n a n c e Se rvi vicc e c la ss 2.15.1 2.15 .1 Effe c t o f m o istur sturee o n str stree ng th a nd st stiiffne ss 2.15.2 De fini niti tio o ns o f se rvi vicc e c la ss ssee s

10 11 11 12 12 12 12

2.16 2. 16 Lo a d d ur uraa ti tio on 2.16. 2. 16.1 1 Effe c t o f lo a d d ur uraa ti tio o n o n str tree ng th a nd sti tifffne ss 2.16.2 2.16 .2 De fini niti tio o ns o f lo a d d ura ti tio o n c la ss ssee s 2.17 2. 17 Fa c tor torss to a llow for e ffe c ts of m oi oisstur turee a nd loa d d ura ura ti tion on 2.17. 2. 17.1 1 Str tree ng th m o d ific a ti tio o n fa c tor tor,, k mod mod 2.17.2 2.17. 2 2.17.3 2.17 .3

3

De fo rm a ti tio o n m o d ific a ti tio o n fa c tor tor,, k def La rg e se c ti tio o ns o f sol soliid ti tim mbe r

12 12 13 13 13 13 15

De sig n p rinc ip le s

16

3.1

Ac ti tio o ns 3.1.1 3.1. 1 Typ e s o f a c ti tio on 3.1. 3. 1.2 2 Ch a ra c te risti ticc va lue s o f a c ti tio o ns 3.1. 3. 1.3 3 De sig n va lue s o f a c ti tio o ns 3.1. 3. 1.4 4 Actio Acti o n c o m b ina ti tio o ns Lim it sta te s 3.2.1 Ulti tim m a te lim it sta te s (U (UL LS) 3.2.2 Se rvi vicc e a b ility lim it sta te s (S (SL LS) 3.2. 3. 2.3 3 Cre e p e ffe c ts in a sse m b lie s 3.2. 3. 2.4 4 Use o f fra m e a na lys ysiis p ro g ra m s 3.2.5 Flo o r vi vib b ra ti tio on Tim b e r m a te ria ls 3.3.1 3.3. 1 Str truc uc tura l ti tim m b e r m a te ria ls 3.3. 3. 3.2 2 Dime nsi nsion on s a nd tol tolee ra nc e s 3.3. 3. 3.3 3 Ch a ra c te risti ticc va lue s 3.3. 3. 3.4 4 De sig n va lue s o f str tree ng th p ro p e rti tiee s 3.3.5 3.3. 5 De si sig g n va lue s o f sti stifffne ss p ro p e rti tiee s Prote Pr ote c ti tive ve tr tree a tme nts 3.4. 3. 4.1 1 De c a y 3.4. 3. 4.2 2 Insec t a tta c k 3.4. 3. 4.3 3 Pree se rva ti Pr tive ve tr tree a tme nt 3.4.4 Surfa c e fini nishe she s 3.4. 3. 4.5 5 Co rro sio n o f m e ta l p a rts 3.4. 3. 4.6 6 Sp re a d o f fla m e

16 16 16 16 16 18 18 20 25 25 25 26 26 26 32 38 48 48 48 48 49 49 50 51

Ma te ria l sp e c ific a ti tio o ns 3.5.1 3.5. 1 O ve rvi viee w 3.5.2 Dim Di m e nsi nsio o ns 3.5.3 Ma te ria ls 3.5. 3. 5.4 4 Prote Pr ote c ti tive ve tr tree a tme nts 3.5.5 Ma rki king ng

52 52 52 53 53 53

3.2

3.3

3.4 3. 4

3.5 3. 5

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4

Ini niti tiaa l d e si sig gn

58

4.1 4.1 4.2

58 58 58 58 58 59 59 62 63 63

4.3

Sc op e Priinc ip le s o f ini Pr niti tiaa l d e si sig gn 4.2.1 4.2. 1 G e ne ra l p rinc ip le s 4.2.2 4.2. 2 Ve rti ticc a l lo a d tr traa nsf nsfee r 4.2.3 4.2. 3 Ho rizo nta l lo a d tr traa nsf nsfee r 4.2. 4. 2.4 4 Loa d c a se s 4.2.5 Sizi zin ng 4.2.6 4.2. 6 O utl utliine o f ini niti tiaa l d e si sig g n p ro c e ss Fire re si sista sta nc e 4.3.1 4.3. 1 Introd uc ti tio on

4.3.2 4.3. 2 4.3.3 4.3. 3

Insul nsulaa ti tio o n m e tho d Sa c rific ia l ti tim m b e r m e tho d

63 65

4.4 4.4 4.5 4.6 4. 6

Move m e nt Dura b ility Ac o usti usticc , the rm a l insul nsulaa ti tio o n a nd a ir ti tig g htne ss re q ui uirre m e nts 4.6. 4. 6.1 1 G e ne ra l 4.6.2 4.6. 2 Ac o usti usticc 4.6.3 The rma l insul nsulaa ti tio on 4.7 4. 7 De nsi nsiti tiee s a nd we ig hts 4.8 Ro o fs 4.8.1 4.8. 1 Introd uc ti tio on 4.8.2 Trusse d ra fte r ro o fs 4.8.3 C ut ro o fs 4.8. 4. 8.4 4 Oth e r type s o f ro o f 4.9 Flo o rs 4.9.1 4.9. 1 Introd uc ti tio on 4.9. 4. 9.2 2 Joissts a nd b e a ms Joi 4.9.3 4.9. 3 De c king 4.10 Wa lls 4.10.1 4.10 .1 C o lum ns 4.10.2 Tim b e r fra m e wa lls 4.11 4. 11 Co nne c ti tion on s 4.11.1 4.11 .1 Introd uc ti tio on 4 .1 .1 1. 1.2 C h o o sin sin g a c o n n e c t io io n m e t h o d 4.12 Esti stim m a ti ting ng 4.13 4. 13 Co m p le ti ting ng the d e sig n 4.13.1 4.13 .1 Introd uc ti tio on 4.13.2 4.13 .2 C he c king o f a ll informa ti tio on 4.13 4. 13.3 .3 Pree p a ra ti Pr tion on of a list of d e sig n d a ta 4.13.4 4.13. 4 4.13.5 4.13 .5

65 65 65 65 65 66 66 68 68 70 70 70 72 72 72 73 74 74 76 77 77 77 78 84 84 84 85

Ame nd m e nt o f d ra wi wing ng s a s a b a sis fo r fina l c a lc ul ulaa ti tio o ns Fina l d e si sig g n c a lc ul ulaa ti tio o ns

85 86

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5

De ta ile d d e sig n rul ulee s 5.1 5.1 5.2 5. 2

5.3 5. 3

5.4 5. 4

87

Ge ne ra l d e sig n p roc e d ur uree for str truc uc tur turaa l me mb e rs 87 Fle xur uraa l m e m b e rs (s (so o lid re c ta ng ul ulaa r se c ti tio o ns) 87 5.2. 5. 2.1 1 Str traa ig ht b e a m s 87 5 .2 .2 .2 .2 Ta p e re d , c u rv rv e d a n d p it c h e d c a m b e re d g lu la la m b e a m s (EC 5 6 .4 .4 .3 .3 ) 9 0 Mem b e rs sub je c t to a xia l c om p re ssion (s (sol oliid re c ta ng ul ulaa r me m b e rs) 92 5.3. 5. 3.1 1 Me m b e rs sub je c t to a xia l c o m p re ssio n o nl nly y (E (EC5 C5 6. 6.3. 3.2) 2) 92 5 .3 .3 .2 .2 Me m b e rs su b je c t t o a xia l c o m p re ssio n a n d b e n d in g a b o u t t h e  y   a xis o nl nly y (E (EC C 5 6.2.4, 6.3. 6.3.2 2 a nd 6.3.3) 93 5 .3 .3 .3 .3 Me m b e rs su b je c t t o a xia l c o m p re ssio n a n d b e n d in g a b o u t b o t h a xe s (EC (E C 5 6.2.4, 6.3. 6.3.2 2 a nd 6.3.3) 93 Me m b e rs sub je c t to a xia l te nsi nsio on 94 5.4.1 5.4. 1 Me m b e rs sub je c t to a xia l te nsi nsio o n o nl nly y (E (EC C 5 6.1 6.1.2) .2) 94 5.4. 5. 4.2 2 Me mb e rs sub je c t to a xia l te nsi nsion on a nd be nd ing a b ou t the y a xis on ly (EC (E C 5 6.1 6.1.2 .2 a nd 6.2 6.2.3) .3)

94

5 .4 .4 .3 .3 5.5 5. 5

5.6 5.7 5. 7 5.8 5. 8

5.9 5.9 5.10 5.1 0

5.11 5.1 1

Me m b e rs su b je c t t o a xia l t e n sio n a n d b e n d in g a b o u t b o t h a xe s (EC (E C 5 6.1 6.1.2 .2 a nd 6.2 6.2.3) .3) Flitc h b e a m s 5.5.1 5.5. 1 Introd uc ti tio on 5.5. 5. 5.2 2 Sc op e 5.5. 5. 5.3 3 De sig n me thod 5.5. 5. 5.4 4 Str tree ng th c he c ks 5.5.5 Sta b ility 5.5.6 5. 5.6 Bo lts fo r UDL DLss 5.5.7 Bo lts fo r p o int lo a d s 5.5.8 5.5. 8 Bo lts a t re a c ti tio o ns 5.5. 5. 5.9 9 Dista nc e s, sp a c ing s a nd ori oriee nta ti tion on Pro Pr o vi vid d ing str struc uc tura l sta b ility Bra c ing of c om p re ssion me mb e rs a nd of b e a m or tr trus usss sys yste te ms Ho rizo nta l d ia p hr hraa g m s 5.8.1 Sim p le sol solution ution 5.8. 5. 8.2 2 Eur uroc oc od e 5 me thod Ve rti ticc a l d ia p hr hraa g m s Fire re si sista sta nc e 5.10.1 5.10 .1 Introd uc ti tio on 5.10.2 5.10 .2 Pro Pr o te c ti tio o n b y insul nsulaa ti tio on 5.10 5. 10.3 .3 Ca lc ul ulaa ti tion on of re d uc e d c ross oss--se c ti tion on 5.10. 5. 10.4 4 Rul ulee s fo r the a na lys ysiis o f re d uc e d c ro ss-se c ti tio o ns Bui uilld ing a ro b ust st strruc tur turee

vi

 

95 95 95 95 96 97 98 98 99 99 99 99 99 100 100 10 0 100 10 0 102 102 102 103 104 10 4 105 106

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6

Co nne c ti tio o ns

109 10 9

6.1 6.2 6. 2

109 109 10 9 109 109 1 09 09 113 117 11 7 117 120 123 1 24 24 124 126 12 6 127 134 13 4 134 134

6.3 6. 3

6 .4 .4

6.5 6. 5

Introd uc ti tio on Dowe l ty typ p e c on ne c ti tion on s 6.2.1 6.2. 1 Introd uc ti tio on 6.2.2 6.2. 2 Sp e c ific a ti tio on 6 .2 .2 .3 .3 La t e ra l lo a d c a p a c it y o f a t im im b e r c o n n e c t io io n 6.2.4 6.2. 4 De si sig g n va lue s Na ile d c on ne c ti tion on s 6.3.1 6.3. 1 Introd uc ti tio on 6.3.2 6.3. 2 La te ra lly lo a d e d na ils 6.3.3 Axiia lly lo a d e d na ils Ax Sc re w e d c o n n e c t io io n s 6.4.1 6.4. 1 Introd uc ti tio on 6.4. 6. 4.2 2 La te ra lly lo a d e d sc re ws 6.4.3 6.4. 3 Axiia lly lo a d e d sc re ws Ax Bol olte te d c on ne c ti tion on s 6.5.1 6.5. 1 Introd uc ti tio on 6.5. 6. 5.2 2 La te ra lly lo a d e d b o lts

6.6 6. 6

6.7

6.8 6. 8

6.5.3 6.5.3 Axiia lly lo a d e d b o lts Ax Dowe lle d c on ne c ti tion on s 6.6.1 6.6. 1 Introd uc ti tio on 6.6. 6. 6.2 2 La te ra lly lo a d e d d ow e ls G lue d jo ints 6.7.1 6.7. 1 Introd uc ti tio on 6.7.2 De si sig gn 6.7.3 6.7. 3 Adh e si sive ve s G lue d ro d s 6.8.1 6.8. 1 Introd uc ti tio on

135 135 141 14 1 141 141 146 146 147 148 151 151

6.8.2 De si sig gn 6.9 3-d im e nsi 3-d nsio o na l na iling p la te s 6 .1 .1 0 P u n c h e d m e t a l p la t e fa st e n e rs a n d n a ilin g p la t e s 6.10.1 6.10 .1 Introd uc ti tio on 6 .1 .1 0. 0.2 P u n c h e d m e t a l p la t e fa st e n e rs 6.10.3 6.10 .3 Na iling p la te s 6.11 6. 11 Tim b e r c o nne c tors 6.11.1 6.11 .1 Introd uc ti tio on 6.11.2 De si sig gn 6.12 6. 12 Pr Pro o p rie ta ry c o nne c tors 6.13 Jo int sl sliip 6.13.1 6.13 .1 Introd uc ti tio on 6.13.2 Slip m o d ul ulus us 6.13.3 6.13 .3 Insta nta ne o us sl sliip 6.13.4 Fin a l sl sliip 6.13.5 Alllo wi Al wing ng fo r sl sliip in fra m e a na lys ysiis p ro g ra m s 6.14 6.1 4 C o nn e c ti tio o ns in fire

151 155 1 56 56 156 1 57 57 157 157 157 157 160 160 160 160 161 161 161 161

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7

Ro o fs

163

7.1 7. 1

Ge ne ra l d e sig n re q ui uirre m e nts

163 16 3

7.4

7.1.1 7.1.1 Fun c ti tio o ns o f a ro o f 7.1. 7. 1.2 2 Da ta re q ui uirre d 7.1.3 Ac ti tio o ns 7.1.4 Bra c ing 7.1.5 Ra ise d ti tiee tr trusse usse s 7.1.6 Se rvi vicc e a b ility Fla t ro o fs Trusse d ra fte rs 7.3.1 7.3. 1 Introd uc ti tio on 7.3.2 7.3. 2 De si sig g n informa ti tio on 7.3.3 Sta b ility 7.3.4 7.3. 4 Notc hi hing ng a nd d rilling Site b ui uillt c ut ro o fs

163 163 164 165 165 165 16 5 165 169 169 169 170 170 170

7.5 7.6 7.7

Tim b e r tr trusse usse s Pyraa m id ro o fs Pyr G rid she lls

173 174 174

7.2 7.3

8

Flo o rs

175

8.1 8. 1

175 175 175

Ge ne ra l d e sig n re q ui uirre m e nts 8.1.1 8.1. 1 Fun c ti tio o ns o f a flo o r

8.2 8.3

8.4

8.5 8.6 8.7 8. 7

9

8.1.2 Ac ti tio o ns 8.1.3 8.1. 3 De si sig g n informa ti tio on Typ e s o f ti tim m b e r flo o r Ma te ria ls 8.3.1 8.3. 1 Sp e c ific a ti tio on 8.3.2 8.3. 2 Be a m s 8.3.3 Jo ists 8.3.4 Strutting 8.3.5 8.3. 5 De c king 8.3.6 Fixi xin ng Flo o r d e si sig gn 8.4. 8. 4.1 1 G e ne ra l 8.4.2 Ulti tim m a te lim it sta te s 8.4.3 Se rvi vicc e a b ility lim it sta te s 8.4.4 Sta irw e ll tri trim m m ing 8.4.5 8.4. 5 Bui uillt up b e a m s Fire re si sista sta nc e Ro b ustne ss Ac ou sti ticc a nd the rm a l re q ui uirre m e nts 8.7.1 8.7. 1 Ac o usti usticc 8.7.2 The rma l

175 175 176 177 177 17 7 177 180 18 0 180 180 181 182 182 182 182 185 186 187 187 188 18 8 188 188

Low rise op e n fra m e c o ns nstr truc uc ti tio on

189 18 9

9.1 9. 1

189 189 189 189 189 18 9

Forms of op e n fra me c on str truc uc ti tion on 9.1. 9. 1.1 1 Sc o p e 9.1.2 9.1. 2 C o nstr nstruc uc ti tio o n p rinc ip le s 9.1. 9. 1.3 3 Se le c ti tion on of ty typ p e of fra me a nd ma te ria ls

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9.2

9.3 9. 3

9.4 9. 4

De si sig gn 9.2.1 Priinc ip le s Pr 9.2. 9. 2.2 2 Fra m e im p e rf rfee c ti tio o ns 9.2. 9. 2.3 3 Sta b ility a nd b ra c ing 9.2. 9. 2.4 4 Ba se c on ne c ti tion on s Co nstr nstruc uc ti tio o n d e ta ils 9.3. 9. 3.1 1 Situa ti tion on s to b e a voi void ded 9.3.2 9.3. 2 Ba se d e ta ils 9.3.3 9.3. 3 Pin Pi n jo inti nting ng te c hn iq ue s 9.3.4 Sti tifff jo int ing te c hn iq ue s Move m e nt

10 Pl Plaa tf tfo o rm ti tim m b e r fra m e b ui uilld ing s 10.1 Introd uc ti 10.1 tio on 10.2 10 .2 Desi Desig g n p roc e d ur uree 10.3 Ac ti tio o ns 10.3.1 10.3 .1 Wind Wi nd lo a d s 10.4 10. 4

10.5 10. 5

10.3.2 10.3. 2 Oth e r a c ti tio o ns Ma te ria l se le c ti tio on 10.4.1 Ro o fs 10.4.2 Flo o rs 10.4.3 Wa lls O ve ra ll sta b ility c a lc ul ulaa ti tio o ns 10.5.1 10.5 .1 G e ne ra l (E (EC C 0 6.4 6.4.1( .1(1)( 1)(aa )) 10.5.2 10.5 .2 O ve rturni turning ng 10.5.3 Slid in g

190 190 190 190 192 19 2 192 192 19 2 193 193 194 194 19 4

195 195 195 19 5 195 195 19 5 199 199 199 199 200 204 204 206 210

10.6 10.6 10.7 10.8

10.9 10.9 10.10 10. 10 10.1 10 .11 1

10.5.4 Ro o f up lift 10.5.5 Ro o f sl sliid in g Ro o f d e si sig gn Flo o r d e si sig gn Wa ll d e si sig gn 10.8. 10. 8.1 1 Ra c king re sista nc e o f ti tim m b e r fra m e wa lls 10.8. 10. 8.2 2 Ra c king re sista nc e in a symm e tr triic b ui uilld ing s 10.8. 10. 8.3 3 Alte Al te rna ti tive ve m e tho d s o f p ro vi vid d ing ra c king re sista nc e 10.8.4 Ma son ry wa ll ti tiee s 10.8.5 De si sig g n o f wa ll stud s 10.8.6 De si sig g n o f lint e ls 10.8.7 10.8 .7 Ho rizo nta l d e fle c ti tio o n o f she a r wa lls Fo und a ti tio o ns Fire re si sista sta nc e Move m e nt 10.11.1 10.1 1.1 Introd uc ti tio on 10.11. 10. 11.2 2 Moi Moisstur turee m o ve m e nt 10.11. 10. 11.3 3 Move m e nt fro m ind uc e d str tree sse s

210 211 212 212 213 213 224 226 226 227 228 228 228 229 229 22 9 229 229 229

10.11.4 10.11. 4 10.11. 10. 11.5 5 10.11.6 10.1 1.6 10.11.7 10.1 1.7

229 230 230 231

Inte rf rfaa c e se ttl ttlee m e nt Ma so nr nry y e xp a nsi nsio on Difffe re nti Di ntiaa l m o ve m e nt Move m e nt jo ints

ix

timb mb e r b ui uilld ing str struc tur turee s to Eur Euroc oc od e 5 IStruc ructE tE/ TRADA  Ma nua l for the d e sig n of ti

 

10.12 10. 12 O the r re q ui uirre m e nts 10.12.1 10.1 2.1 Ac o usti usticc 10.12.2 The rma l 10.13 10. 13 Ro b ustne ss o f p la tf tfo o rm ti tim m b e r fra m e 10.14 10. 14 Pl Plaa tf tfo o rm ti tim m b e r fra m e a b o ve 4 store ys

1 1 C h e c kin g a n d sp e c ific a t io io n g u id id a n c e 11.1 11 .1 Ge ne ra l c he c king re q ui uirre me nts 11.1.1 11.1 .1 Lo c a l Autho rity c he c king 11.1 11 .1.2 .2 Ge ne ra l c he c king 1 1. 1.2 C o d e s a n d st a n d a rd s 11.3 11. 3 Ma te ria l spe c ific a ti tio o ns 1 1. 1.4 P ro ro t e c t io io n a g a in st st d e c a y a n d in se se c t a t ta ta c k 1 1. 1.5 De fle c t io io n a n d c re e p 11.6 Trusse d ra fte r ro o fs 11.7 Flo o rs 11.8 11. 8 Pl Plaa tf tfo o rm ti tim m b e r fra m e 11.9 11. 9 Ch e c king a id s

12 Wor ork km a ns nshi hip p , ins nsta ta lla ti tion on , c o ntr ntro o l a nd m a inte na nc e 12.1 12.1 12.2 12. 2

G e ne ra l Me m b e rs 12.2. 12. 2.1 1 Co nd iti tio o n o f ti tim m b e r m e m b e rs 12.2. 12. 2.2 2 Moisstur Moi turee c o nte nt 12.2.3 Dim Di m e nsi nsio o ns 12.2.4 Mod ific a ti tio o ns 12.2. 12. 2.5 5 Tre a tme nt o f c ut surf urfaa c e s 12.3 Co nne c ti 12.3 tion on s 12.3. 12. 3.1 1 G e ne ra l 12.3. 12. 3.2 2 Na ile d c o nne c ti tio o ns

231 231 231 231 232

23 3 233 233 233 233 23 3 2 34 34 234 2 34 34 2 34 34 234 235 235 235

236 23 6 236 236 236 236 236 237 237 237 23 7 237 237

12.3.3 12.3 .3 Sc re we d c on ne c ti tion on s 12.3. 12. 3.4 4 Bo lte d c o nne c ti tio o ns 12.3 12 .3.5 .5 Dow e lle d c on ne c ti tion on s 1 2. 2.3 .6 .6 C o n n e c t io io n s m a d e w it it h t im im b e r c o n n e c t o rs rs 12.3. 12. 3.7 7 Adhe sive ly b o nd e d jo ints 12.4 Trusse d ra fte rs 12.5 12 .5 Stor toraa g e a nd ha nd ling 12.5 12 .5.1 .1 Prote Pr ote c ti tion on of ma te ria ls a nd c om p on e nts 12.5.2 12.5 .2 Ha nd ling 12.6 12. 6 As Assse m b ly, e re c ti tio o n a nd insta lla ti tio on 12.6. 12. 6.1 1 G e ne ra l 12.6.2 Trusse d ra fte rs 12.6.3 Flo o rs 12.7 12. 7 Tre a tm e nts 12.7 12 .7.1 .1 Pree se rva ti Pr tive ve a nd fla me re ta rd a nt tr tree a tme nts 12.7.2 12.7.2 12.7 12 .7.3 .3

x

Anti-c o rro si Anti-c sive ve tr tree a tm e nts De c ora ti tive ve tr tree a tme nts

 

237 237 238 238 23 8 2 38 38 238 239 239 23 9 239 23 9 239 239 239 239 240 247 2 47 247 247 24 7

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12.8 12. 8

1 2. 2.9

Pro d uc ti Pro tio o n a nd site c o ntr ntro ol 12.8.1 12.8 .1 C o ntr ntro o l p la n 12.8.2 12.8 .2 Insp e c ti tio on Ma in t e n a n c e

247 247 248 2 48 48

12.9.1 12.9.2 12.9. 12. 9.3 3 12.9.4 12.9 .4 12.9. 12. 9.5 5

248 248 248 248 248

Re sp o n si sib b ility Tig hte ni ning ng o f b o lts Anc illa ry c o m p o ne nts Str truc uc tura l m e ta l-wo rk Oth e r m a tte rs

Re fe re n c e s

24 9 24

App e nd ix A – De sig n va lue s fo r a ro b ust d e sig n

255

Ap p e nd ix B – Use ful UK o rg a ni nisa sa ti tio o ns

258

timb mb e r b ui uilld ing str struc tur turee s to Eur Euroc oc od e 5 IStruc ructE tE/ TRADA  Ma nua l for the d e sig n of ti

 

C D Cont Content ents s Pa rt 1 Ma Ma te ria l p ro p e rti tiee s C D1. D1.1 1 Pr Pro p e rti tiee s o f sol soliid ti tim m b e r str stree ng th c la sse s CD1.2 CD1.2 CD1.3 CD1. 3 CD1.4 CD1. 4 CD1.5 CD1. 5 C D1. D1.6 6 C D 1. 1. 7

Prrop e rti P tiee s Prop e rti Prop tiee s Prop e rti Pr tiee s Pro p e rti Pro tiee s Pro p e rti Pro tiee s Pro p e rt ie Pr ie s

of of of of of of

sstr tree ng thth-g g ra d e d oa k  gra d e TH1 Ame gra Ame ric a n h a rd wo od s glue d la mi glue mina na te d soft oftwo wo od str tree ng th c la sse s so m e c o m m o n typ e s of LVL so O SB/ 3 a nd O SB/ 4 w o o d p a rt ic ic le b o a rd (c h ip ip b o a rd )

For ma te ria l p rop e rti tiee s of p lywoo d re fe re nc e sho ul uld d b e m a d e to BS BS 52 5268 68--2 Ta b le s 40 to to 56 56,, a nd to Se Se c ti tion on 3. 3.3. 3.3 3 of the Ma nua l for c on ve rsion formul ormulaa e .

P a rt 2 La La t e ra lly lo lo a d e d fa st e n e r sp re a d sh e e t s CD2.1 CD2. 1 Ca lc ul ulaa ti tion on b a sis for for fa fa ste ne r sp re a d she e ts CD2.2 CD2.2 C D 2. 2. 3 CD2.4 CD2. 4 CD2.5 CD2. 5

Na ile d c on ne c ti Na tion on s Scc re w e d c o n n e c t io S io n s Bolte Bol te d c on ne c ti tion on s Dowe lle d c on ne c ti tion on s

Pa rt 3 Pr Pro o vi vissio n o f re str traa int a g a inst the ro ta ti tio o n o f ind ivi vid d ua l tim ti m b e r fra m e wa lls Pa rt 4 De sig n va lue s fo r ti tim m b e r c o nne c tor torss P a rt 5 C o n t a c t d e t a ils fo r t h e m a n u fa fa c t u re re rs o f so m e tim ti m b e r c o ns nstr truc uc ti tio o n p ro d uc ts Pa rt 6 C o nta c t inf info o rm a ti tio o n o f sp o ns nso o r o rg a ni nissa ti tio o ns

xi

xii

 

tim m b e r b ui uilld ing struc struc tur turee s to Eur Euroc oc od e 5 IStruc uctE tE/ TRADA  Ma nua l fo r the d e sig n of ti

 

Tables Ta b le 2.1

De fin it io n o f se rv ic e c la sse s a n d e xa m p le s

12

Ta b le 2.2

Lo a d d u ra t io n c la sse s

13

Ta b le 2.3

Va lue s of k mod  mod 

14

Ta b le 2.4

def  Va lue s of k def 

14

Ta b le 3.1

P a rt ia l lo a d fa c t o rs fo r ULS

17

Ta b le 3.2

Fa c tor torss for for the re p re se nta ti tive ve va lue s of va va ria b le a c ti tion on s for for the b ui uilld ing s c o v e re d b y t h is is M  Ma a nua nuall 

17

Ta b le 3.3

De si sig n v a lu lu e s o f b e n d in in g m o m e nt n t s – d o m e st st ic fl flo o r b e a m e xa xa m p le le

20

Ta b le 3.4

Re c o m m e n d e d v e rt rt ic ic a l d e fle c t io io n li lim it it s b a se d o n sp a n , l

23

Ta b le 3.5

Re c o m m e n d e d h o rizo n t a l d e fle c t io n lim it s

24

Ta b le 3.6

St ru c t u ra l t im b e r m a t e ria ls

27

Ta b le 3.7

Dim e n sio n a l t o le ra nc n c e s fo r so lid t im b e r, g lu la m a nd n d LVL

28

Ta b le 3.8

P re fe rre d so ft w o o d size s

29

Ta b le 3.9

C LS/ ALS (p la n e d a ll ro u n d ) so ft w o o d size s

29

Ta b le 3.10

P re fe rre d h a rd w o o d size s

29

Ta b le 3.11

Typ ic ic a l g lu lu la m se s e c t io ns n s – b a se s e d o n Im Im p e ri ria l size s ( m o re c o m m o n )

30

Ta b le 3.12

Typ ic a l g lu la m se c t io n s – Me t ric size s

30

Ta b le 3.13

Typ ic a l LVL se c t io n s

31

Ta b le 3.14

Ch a ra c te risti ticc p rop e rti tiee s for som som e c om mo n str stre ng th c la sse s of sol soliid softwood

33

Ta b le 3.15

Ch a ra c te risti ticc va lue s for som e c om mo n str stree ng th c la sse s of soft oftwo wo od g lul ulaa m c o m p lyi ying ng wi with th BS BS EN 14080

34

Ta b le 3.16

Ch a ra c te risti ticc va lue s fo r som e c o m m o n type s o f LVL

35

Ta b le 3.17

Ra n g e s o f c h a ra ra c t e ri rist ic va v a lu lu e s fo r c o m m o n st ru c tu t u ra l p ly lyw o o d s

36

Ta b le 3.18

C h a ra c t e rist ic v a lu e s fo r O SB/ 3

37

Ta b le 3.19

P a rt ia l fa c t o rs fo r m a t e ria l p ro p e rt ie s a n d c o n n e c t io n s

38

Ta b le 3.20

P rin c ip a l m e m b e r a n d syst e m m o d ific a t io n fa c t o rs

38

Ta b le 3.21

Effe c ti tive ve le ng ths in in b e nd ing , lef  

42

Ta b le 3.22

Effe c ti tive ve le ng ths in in c o m p re ssio n, lef 

44

Ta b le 3.23

Fa c tor torss for d e te rmi mini ning ng the ne c e ssity of p re se rva ti tive ve tr tree a tme nt

49

Ta b le 3.24

Re c o m m e n d a t io io n s fo r p re se rv a t iv iv e t re re a t m e n t o f n o n - d u ra ra b le t im im b e rs

50

Ta b le 3.25

Exa m p le s of mini minim m um sp e c ific a ti tion on s for for ma te ria l p rote c ti tion on a g a ins nstt c or orrrosi osion on of fa fa ste ne rs a nd ste e l p la te s

51

Ta b le 3.26

O u te te r t h re re a d d ia ia m e t e rs rs c o rr rre sp s p o n d in in g to t o st st a n d a rd w o o d sc sc re re w g a u g e s

53

Ta b le 3.27

So m e b a si sic sp sp e c if ific a t io ns n s fo r t im b e r a n d p la la st s t e rb rb o a rd rd m a t e ri ria ls ls

54

Ta b le 3.28

Ma te t e ri ria l sp e c ific a ti t io n s fo r so m e c o m m o n st ru c tu t u ra l p ly lyw o o d s

55

Ta b le 3.29

Ba sic sp e c ific a t io n s fo r m e c h a n ic a l fa st e n e rs

56

timb mb e r b ui uilld ing str struc tur turee s to Eur Euroc oc od e 5 IStruc ructE tE/ TRADA  Ma nua l for the d e sig n of ti

xiii

 

Ta b le 4.1

Va lue s of k mod   to use in se rvi vicc e c la ss ssee s 1 a nd 2 fo fo r sol soliid ti tim m b e r, g lul ulaa m , LVL mod  to a n d p ly w o o d

59

Ta b le 4.2

Ap p roxi oxim m a te str tree ng ths of tim tim b e r c on ne c ti tion on s in in te rms of unjoi unjointe nte d m e m b e r st re re n g t h

60

Ta b le 4.3

Ma xim u m d e p t h t o b re a d t h ra ra t io io s o f so so li lid t im im b e r b e a m s t o a v o id id la t e ra ra l to rsi sio o na l b uc kling

63

Ta b le 4.4

 No tio n a l c h a rr rriin g ra te s

65

Ta b le 4.5

De n sit ie s a n d w e ig h t s

66

Ta b le 4.6

St ru c t u ra l fo rm s fo r t im b e r ro o fs

69

Ta b le 4.7

Ma xim u m c le a r sp a n s in m e t re s fo r C 1 6 ro o f m e m b e rs

71

Ta b le 4.8

Ma xi xim u m c le le a r sp a ns n s in m e tr tre s fo r C 1 6 d o m e st st ic fl flo o r jo ist s

73

Ta b le 4.9

G u id id e t o m a xim u m sp a n s fo r flo o r d e c kin g m a t e ria ls fo r d o m e st ic ic flo o rin g

74

Ta b le 4.10

Desig n tota l a xia l loa d c a p a c iti Desig tiee s for sq sq ua re c ol olum um ns in in soli solid ti timb mb e r a nd g lul ulaa m, with with no la te ra l b e nd ing , se se rvi vicc e c la sse s 1 a nd 2

75

Ta b le 4.11

Lin t e l size s fo r 8 9 m m t h ic k e xt e rn a l w a lls

78

Ta b le 4.12

Lin t e l size s fo r 1 4 0 m m t h ic k e xt e rn a l w a lls

78

Ta b le 4.13

C h o ic e o f c o n n e c t io n t yp e

80

Ta b le 4.14

C o m m e n t a ry t o Ta b le 4 .1 3

82

Ta b le 5.1

C a lc lc ul u la ti t io n o f b e nd n d in g a nd n d sh sh e a r d e fl fle c t io n in t im b e r b e a m s

91

Ta b le 5.2

Lo a d d ist rib u t io n e xp re ssio n s

96

Ta b le 5.3

Va lue s of k fire fire

103 10 3

 No tio n a l d e si sig g n c h a rr rriin g ra te fo r m e m b e rs e xp o se d o n m o re th a n o n e sid si d e to fi firre

105 10 5

Ta b le 5.5

Metho d s of a c hi hiee vi ving ng a rob us ustt c on str truc uc ti tion on

107 10 7

Ta b le 6.1

C o m m o n ly a v a ila b le c o rro sio n re sist a n t n a il size s

1 18

Ta b le 6.2

Minim Mini m um sp a c ing s a nd d ista nc e s for for na ils a nd sma ll sc re ws without without  p re d ri rillle d h o le s c o n n e c tin ting g so lid tim b e r o r g lu la m

119 11 9

Ta b le 6.3

Minim Mini m um sp a c ing s a nd d ista nc e s for for na ils a nd sma ll sc re ws without without  p re d ri rillle d h o le s c o n n e c tin ting g p lyw o o d o r O SB to tim b e r 

119 11 9

Ta b le 6.4

Va lue s of nef  for   for co nne c ti tion on s ma d e wi with th na ils a nd sm a ll sc re ws without without  p re d ri rillle d h o le s in so ftw o o d s u p to stre n g th c la ss C 40

120 12 0

Ta b le 6.5

C h a ra c t e rist ic ic la t e ra ra l lo a d c a p a c it y p e r fa st e n e r in sm o o t h n a ile d 2-m 2m e m b e r ti timb mb e r-ti timb mb e r c on ne c ti tion on s, not p re d rille d

120 12 0

Ta b le 6.6

C h a ra c t e rist ic ic la t e ra ra l lo a d c a p a c it y p e r fa st e n e r in sm o o t h n a ile d 2-m 2m e m b e r p lywoo d -ti timb mb e r c on ne c ti tion on s, not p re d rille d

121 12 1

Ta b le 6.7

C h a ra c t e rist ic ic la t e ra ra l lo a d c a p a c it y p e r fa st e n e r in sm o o t h n a ile d

122 12 2

Ta b le 5.4

2-m 2m e m b e r O SB-ti tim m b e r c o nne c ti tio o ns, no t pred rille d Ta b le 6.8

Ch a ra c te risti ticc wi withd thd ra wa l re sista nc e of a smo oth n a il in N pe r m m of p oi oints ntsiid e p e ne tr traa ti tion on into sid e g ra in w ith a mi mini nimu mu m p oi oints ntsiid e  p e n e tra tio n o f 12 d 

xiv

 

124 12 4

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Ta b le 6.9

C o m m o n size s o f w o o d sc re w

125

Ta b le 6.10

C o m m o n size s o f c o a c h sc re w

125

Ta b le 6.11

Min iim m u m sp sp a c in g s a n d e d g e d iisst a n c e s fo r a xia lly lo a d e d w o o d sc s c re w s

128

Ta b le 6.12

C h a ra c t e ri rist ic ic la t e ra ra l lo a d c a p a c it y p e r fa st e n e r in w o o d -sc re w e d 2-m 2-m e mb e r tim tim b e r-tim tim b e r c o nne c tio tio ns, no t pre pre d rille d

12 9

Ta b le 6.13

C h a ra c t e ri rist ic ic la t e ra ra l lo a d c a p a c it y p e r fa st e n e r in w o o d -sc re w e d

13 0

Ta b le 6.14

2-m 2-m e m b e r p lyw o od -t im im b e r c on ne c t ion ion s, not p re d rille d C h a ra c t e ri rist ic ic la t e ra ra l lo a d c a p a c it y p e r fa st e n e r in w o o d -sc re w e d 2-m 2-m e mb e r OSB OSB-timb timb e r c o nne c tio tio ns, no t p re d rille d

13 1

Ta b le 6.15

C h a ra c t e ri rist ic ic la t e ra ra l lo a d c a p a c it y p e r fa st e n e r in c o a c h sc sc re w e d 2-m 2-m e mb e r tim tim b e r-tim tim b e r c o nne c tio tio ns, p re d rille d

13 2

Ta b le 6.16

C h a ra c t e ri rist ic ic la t e ra ra l lo a d c a p a c it y p e r fa st e n e r in c o a c h sc sc re w e d 2-m 2-m e mb e r ste e l-tim tim b e r c o nne c tio tio ns ns,, p re d rille d

13 3

Ta b le 6.17

Min im im u m sp a c in g s a n d d ist a n c e s fo r c o n n e c t iio o n s m a d e w iitt h b o lt lt s a n d la rg e sc re w s

13 4

Ta b le 6.18

Va lue s of

135

Ta b le 6.19

C ha ra c t e rist ic ic la t e ra l loa d c a p a c it y p e r fa st e ne r for 2-m 2-m e m b e r t im im b e r-t im im b e r c on ne c t ion ion s m a d e w it it h 4. 4.6 g ra d e b o lt s

13 6

Ta b le 6.20

C h a ra c t e ri rist ic ic la t e ra ra l lo a d c a p a c it y p e r sh e a r p la n e fo r 3 -m -m e m b e r t im im b e r-t im im b e r c on ne c t ion ion s m a d e w it it h 4. 4.6 g ra d e b o lt s

13 7

C ha ra c t e ri rist ic ic la t e ra ra l loa d c a p a c it y p e r she a r p la ne for 3-m 3-m e m b e r  p lyw o o d -timb -tim b e r-p lyw o o d c o n n e c tio n s m a d e w ith 4.6 g ra d e b o lts

13 8

Ta b le 6.22

C h a ra c t e ri rist ic ic la t e ra ra l lo a d c a p a c it y p e r sh e a r p la n e fo r 3 -m -m e m b e r st e e l-t im im b e r-st e e l c on ne c t io io ns m a d e w iitt h 4.6 4.6 gra gra d e b olt olt s

13 9

Ta b le 6.23

C h a ra c t e ri rist ic ic la t e ra ra l lo a d c a p a c it y p e r sh e a r p la n e fo r 3 -m -m e m b e r t im im b e r-st e e l-t im im b e r c on ne c t ion ion s m a d e w iitt h 4. 4.6 gra gra d e b olt olt s

14 0

Ta b le 6.24

Min im u m sp a c in g s a n d d ist a n c e s fo r d o w e ls

141

Ta b le 6.25

C ha ra c t e rist ic ic la t e ra l loa d c a p a c it y p e r fa st e ne r for 2-m 2-m e m b e r t iim m b e r-t im im b e r c o n n e c t io io n s m a d e w iitt h 4 .6 .6 g ra ra d e d o w e ls

14 2

Ta b le 6.26

C h a ra c t e ri rist ic ic la t e ra ra l lo a d c a p a c it y p e r sh e a r p la n e fo r 3 -m -m e m b e r t iim m b e r-t im im b e r c o n n e c t io io n s m a d e w iitt h 4 .6 .6 g ra ra d e d o w e ls

14 3

Ta b le 6.27

C h a ra c t e ri rist ic ic la t e ra ra l lo a d c a p a c it y p e r sh e a r p la n e fo r 3 -m -m e m b e r st e e l-t im im b e r-st e e l c on ne c t ion ion s m a d e w iitt h 4. 4.6 g ra d e d o w e ls

14 4

Ta b le 6.28

C h a ra c t e ri rist ic ic la t e ra ra l lo a d c a p a c it y p e r sh e a r p la n e fo r 3 -m -m e m b e r t im im b e r-st e e l-t im im b e r c on ne c t ion ion s m a d e w iitt h 4. 4.6 gra gra d e d ow e ls

14 5

Ta b le 6.29

Lo a d -b e a rin g a d h e siv e s a n d t h e ir u se s

149

Ta b le 6.30

Exp o su re c a t e g o rie s fo r lo a d -b e a rin g a d h e siv e s

150

Ta b le 6.31

Minim nim um re c o m m e nd e d sp a c ing s a nd d ist a nc e s for g lue d -in rod rod s in t e rm s of rod rod d ia m e t e r or si sid e le ng t h, d 

15 2

Ta b le 6.21

nef   fo fo r

c o n n e c t io n s m a d e w itit h b o lt lt s, d o w e ls a n d la la rg e sc re re w s

Ta b le 6.32

UK c o n n e c t o r t y p e s a n d size s

158

Ta b le 6.33

Use s o f t im b e r c o n n e c t o rs

159

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Am e n d m e n t s – Ma y 2 00 00 8  

Ta b le 6.34

P ro je c t e d a re a s a n d d e p t h o f c o n n e c t o r g ro o v e s

1 59

Va lue s of K ser    for fa ste ne rs in timb timb e r-to-t to-tiimb e r a nd wo od -b a se d ser  for  p a n e l-to -tim b e r c o n n e c tio n s

160 16 0

Ta b le 7.1

Ro o f lo a d s

1 66

Ta b le 7.2

Exa m p le lo a d c a se s

1 68

Sa m p le sp e c ific a ti tio o ns fo fo r ti tim b e r flo o r co nstr nstruc uc ti tion on s fo fo r d iffe re nt  p e rfo rm a n c e re q u ire m e n ts

178 17 8

Ta b le 8.2

Re c om o m m e nd n d e d ro w s o f st ru t t in g b e t w e e n so lid t im b e r jo ist s

1 80

Ta b le 8.3

Fixin g s fo r so lid t im b e r t rim m e rs a n d t rim m in g jo ist s

1 87

Ta b le 10.1

Va lue s of k masonry masonry

198 19 8

Ta b le 10.2

In su la t io n m a t e ria ls su it a b le fo r t im b e r fra m e w a lls

2 02

Illustr ustraa ti tive ve spe c ific a ti tio o ns fo fo r ti tim m b e r fra m e stud wa lls fo fo r p a rti ticc ul ulaa r  p e rfo rm a n c e re q u ire m e n ts – n o t to b e u se d w ith o u t c o n fi firm rm a tio n fr fro om t h e sp e c ifie d p ro ro d u c t m a n u fa fa c t u re re rs

205 20 5

Ta b le 10.4

Illustr ustraa ti tive ve va lue s o f c pe,10 f  fo o r o ve ra ll sta b ility a nd ra c king re sista nc e ve rific a ti tio o ns

207 20 7

Ta b le 10.5

Desig n la Desig la te ra l loa d c a p a c iti tiee s unde r wi wind nd loa d ing in servi servic e c la ss 2 for for so m e c o m m o n c o n n e c t io io n s m a d e w it it h sm sm o o t h ro ro u n d n a ils d riv e n in in t o

216 21 6

Ta b le 6.35

Ta b le 8.1

Ta b le 10.3

Ta b le 10.6

Ta b le 10.7

C 1 6 t im im b e r   Desig Desi g n la la te ra l loa d c a p a c iti tiee s unde r wi wind nd loa d ing in servi servic e c la ss 2 for for so m e c o m m o n c o n n e c t io io n s m a d e w it it h m a c h in in e d riv e n n a ils d riv e n in in t o C 1 6 t im im b e r  

216 21 6

Desig n la Desig la te ra l loa d c a p a c iti tiee s und e r wi wind nd loa d ing for Type A  p la ste rb o a rd a tt a c h e d to C 16 tim b e r w ith p la ste rb o a rd sc re w s

216 21 6

Ta b le 10.8

Desig n a xia l loa d c a p a c iti Desig tiee s unde r wi wind nd loa d ing in se rvi vicc e c la ss 2 for so m e c o m m o n c o n n e c t io io n s m a d e w it it h fa fa st e n e rs d riv e n in in t o C 1 6 t im im b e r  

217 21 7

Ta b le 10.9

Ba sic ra c kin g re sist a n c e s o f so m e c o m m o n C 1 6 g ra ra d e t im im b e r fra m e w a ll c on fig ur uraa ti tion on s

218 21 8

Ta b le 10.10 Va lue s of k c,90  fo o r m a tc tc hi h in g sin g le wa w a llll st u d s a nd n d b o t t o m ra ilils c,90 f

2 28

Ta b le 12.1

241 24 1

Re q ui uirre me nts for the the ins nsta ta lla ti tion on of woo d -b a se d d e c king for fl floo rs a nd roofs

Ta b le A.1

Re q ui uirre d tyi tying ng fo rc e s fo r ro b ust de ta iling o f a ti tim m b e r b ui uilld ing o r a  b u ild in g w ith tim b e r flo flo o rs

255 25 5

Ta b le A.2

 Na il sp a c in g s re q u ire d to a c h ie ve 5kN/ m la te ra l d e si sig g n c a p a c ity in C 16 so ft ft w o o d u n d e r a c c id e n t a l in st st a n t a n e o u s lo a d in g

256 25 6

Ta b le A.3

Wo o d sc re re w sp sp a c in g s re q u ir ire d t o a c h ie ie v e 5 kN kN/ m la t e ra l d e sig n c a p a c it y in C16 soft softwo wo od und e r a c c id e nta l inst nstaa nta ne ou s loa d ing – no p re d rilling

257 25 7

Ta b le A.4

La t e ra ra l d e sig n c a p a c it y p e r n a il in C 1 6 so so ft ft w o o d u n d e r a c c id e n t a l lo a d ing thr thro o ug h 5mm ste e l a nc ho r str traa p s – no p re d rilling

257 25 7

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Glossary

Accide Acc identa ntall act action ionss

Actions, Action s, usual usually ly trea treated ted as of of insta instanta ntaneo neous us dura duratio tion n but but signi signific ficant ant magnitude, which are unlikely to occur within the design life of the structure, e.g. exceptional snow drifting, impact, fire, explosion or earthquake.

Accidental design

A design situation involving an accidental action.

situation Action

Either a force or load applied to a structure (‘direct action’), or else an imposed deformation (‘indirect action’) such as temperature effects or settlement.

Arris

The line of intersection between two adjacent sides of a piece of timber.

Assembly

A substructure consisting of several members, e.g. a roof truss or floor diaphragm.

Balloon frame construction

2- or 3-storey height timber framed and sheathed wall panels which act as vertical diaphragms and support roofs and floors acting as horizontal diaphragms.

Block Blo ck she shear ar fai failur luree

The tea tearin ring g out out of a block block of mate materia rial, l, usua usually lly as the the result result of a for force ce applied by a group of fasteners which produce a combination of tensile and shear failure around the perimeter of the fastener group.

Buck Bu ckli ling ng le leng ngth th

The dist The distan ance ce bet betwe ween en the the poi point ntss of con contr traf afle lexu xure re in in the the full fully y buck buckle led d mode of a compression member or flange. In BS 5268-23 terms this is the effective length.

Buil Bu ildi ding ng el elem emen entt

A pr prin inci cipa pall par partt of a buil buildi ding ng,, e.g. e.g. roo roof, f, wal wall, l, flo floor or..

Characteris Chara cteristic tic value

The chara characteris cteristic tic value of an actio action n or or materi material al proper property ty is its appr appropria opriate te representative test value, before combination or safety factors are applied to it.

Chipboard

See ‘Particleboard’.

Combin Com binati ation on fact factor or

Usuall Usu ally y referr referred ed to as as a ‘psi fact factor’, or’, a comb combina inatio tion n factor factor adju adjusts sts the the values of variable actions to obtain an appropriate representative design value for the combination.

Comb Co mbin ined ed gl glul ulam am

Glulam Glul am in in whic which h the the oute outerr lami lamina nati tion onss are are made made of of timb timber er whi which ch has has a higher strength than the inner ones.

Compartment floor, compartment wall

A floor or wall which subdivides a large building into compartments of a specified size or volume for fire safety. The use of the term in National Building Regulations is not always consistent.

Component

A member ma made up up of of va various pa parts (e (e.g. a glued th thin-webbed be beam), often manufactured as a product, or part of a force (e.g. the vertical component).

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Connector

See timber connectors.

Creep

The time- and moisture-dependent deformation of a loaded timber member or a laterally loaded mechanically fastened timber connection which occurs in addition to its instantaneous deformation.

Cripple st stud

An ad additional stud wh which st stands on on th the bo bottom rai raill of of a timber fr frame wa wall  panel and supports a sill or the end of a lintel.

Desi De sig gn val alue ue

The des esig ign n val alu ue of an ac acti tio on or gro rou up of ac acti tio ons or mat ater eriial pro rop per erty ty is the appropriate characteristic value or values modified as necessary by the relevant combination and safety factors.

Defo De form rmat atio ion n

The def efle lect ctio ion n or dis ispl plac acem emen entt of a mem emb ber er,, co com mpone nen nt or as asse sem mbly ly,, or the slip in a connection.

Dowelled Dowel led connect connection ion

A conn connectio ection n made with nails, nails, screws, screws, bolts bolts or or round round steel steel dowels. dowels.

Element

A single part of a connection, component, or structural model.

Engineer

In this Manual the Engineer is the person who has overall responsibility for ensuring that the strength, stability and structural serviceability of a building and its elements meet the requirements of the client and the relevant Building Regulations.

Engineered timber  joists

This term principally refers to: •  prefabricated timber floor joists: most commonly I-joists with

•

flanges made of solid timber or a structural timber composite, and webs made of OSB metal open-web timber joists with flanges made of solid timber and punched metal plate webs in a zigzag shape.

Engineered wood  products

This term normally covers structural timber composites and engineered timber joists.

ENV edition

The preliminary edition of a Eurocode published for trial use.

European Technical Approval (ETA)

European Technical Approval (ETA) for a construction product is a favourable technical assessment of its fitness for an intended use. An ETA ET A is used when a relevant releva nt European harmonize h armonized d standard for f or the  product does not exist and is not likely to exist in the near future.

Execution

The act of constructing the works. For timber structures this includes  both fabrication and erection.

Favo Fa vour urab able le ef effe fect ct

A str struc uctu tura rall effe effect ct whi which ch,, in com combi bina nati tion on wit with h othe otherr effe effect cts, s, mak makes es the the overall effect less unfavourable.

Fibree saturation Fibr saturation point point The moistur moisturee content content of timber timber when when all the free free water containe contained d by the cells has drained out but all the water bound within the cell walls is still  present. Fina Fi nall de defo form rmat atio ion n

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The tota The totall defor deforma mati tion on in in a struc structu tura rall membe memberr, compo compone nent nt or or assem assembl bly y  produced by an action or group of actions at the end of its design life, including creep.

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Flitch be beam

A ver erttically lam lamiinated be beam co consisting of of al alternate la laminates of of st steel and either solid timber or a structural timber composite. Most flitch beams consist of a single steel plate bolted between two solid timber sections.

Flitch plate

A plate, usually of steel, sandwich cheed betwee een n two timber members and connected to them with bolts or dowels so that the members act as one. It may also be used to join members end-to-end or at a node.

Frame

An assembly of members capable of carrying actions.

Fundament Fund amental al action action

A quan quantifia tifiable ble persi persistent stent (perm (permanent anent)) or trans transient ient (vari (variable) able) actio action n which is likely to occur with significant magnitude within the design life of the structure.

Fundamental design situation

A design situation which involves only fundamental actions.

Girder tr truss

A multiple tr trussed ra rafter (s (see Se Section 7. 7.3.1.2) th that: • supports a roof width greater than 2.5 times the normal truss spacing in a roof, or • directly supports other trusses, or • supports another girder truss.

Glulam

Glued laminated timber. Consists of lengths of planed timber glued together with a structural adhesive to form larger members with mechanical properties that are better than those of the original timber. It can be made in almost any length and shape, but is generally manufactured in standardised sizes.

Gusset plate

A plate, us usually of of st steel or or pl plywood, us used to to jo join or or re reinforce pr principal members in the same plane.

Hardboard

A panel product made from lignocellulosic fibres combined with an adhesive and bonded under heat and pressure. It is denser than MDF or  particleboard.

Hardwood

Solid timber from a broadleaf species, widely used for beams and columns with medium or high loading. The less dense hardwoods can also be made into high strength glulam, and the more durable species are useful externally and in wet environments. Their relatively fine grain makes them more suitable than softwoods for high quality joinery. joinery.

Homogenous Homogeno us glulam glulam Instantaneous deformation

Glulam made Glulam made with with a singl singlee structu structural ral grade grade of timber timber.. The deformation produced by an action or group of actions at the moment of application, i.e. without any component of creep.

Irreversible serviceability limit state

A serviceability limit state in which the effects of exceeding it remain when the actions causing it are removed.

Kiln dried

Timber which has been dried in a kiln under controlled temperature and humidity.. Structural graded timber is usually dried to a moisture content humidity of 18% to 20% before grading and is stamped ‘KD’.

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Limit states

States be beyond wh which th the st structure no no lo longer sa satisfies th the de design  performance requirements.

Load ca case

An action or a combination of simultaneous actions producing a structural

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effect on a member, component or assembly (see Section 3.2.1.2.). Laminated strand lumber (LSL)

An alternative to large-section solid timber, LSL consists of strands of aspen up to 300mm long and up to 30mm wide. These are coated with a polyurethane adhesive, orientated parallel to the finished length, then  bonded under heat and pressure to form a material superior in strength and stiffness to the wood from which it was made.

Laminated veneer lumber (LVL)

An alternative to large-section timber, consistsadhesive of veneers of timber around 3mm thick gluedsolid together withLVL a structural under  pressure to form a material superior superior in strength and stiffness stiffness to the wood from which it was made.

M.C.

See ‘Moisture content’.

Medium density fibreboard (MDF)

This is a panel product made from wood or other lignocellulosic fibres combined with an adhesive and bonded under heat and pressure. It is not commonly used as a structural material in the UK.

Med ediium-rise

For pl platform timber fr fram amee bu buildings th this ter term m is is us used to mea ean n 4 to 7 storeys.

Member

A beam or column within a structure or assembly.

Moisture content (m.c.)

A measure of the percentage of water in timber, calculated as 100 # (weight of water) / (oven dry weight).

Mult Mu ltip iple le me memb mber er

A mu mult ltip iple le lin linte tel, l, joi joist st,, beam beam,, tr trus usss or tru truss ssed ed raf rafte terr cons consis ists ts of of two two or more single members of one kind joined in parallel so that they act together.

 Nailing plate

A metal plate with holes in it to receive nails - used to join together adjacent timber members in the same plane. Sometimes called a ‘cam  plate’.

 Net projected area

The total area occupied by drilled holes within the plane of a given crosssection. In connection design holes lying within a designated distance of a given cross-section are considered to occur within that cross-section.

 Notified Body

An organisation which has been nominated by a government within the European Union and notified by the European Commission to provide services for assessing the conformity of products to the requirements of the relevant European Directives.

Open frame construction

 

Statically determinate beams and columns stabilised by bracing and/or vertical and horizontal diaphragms, or frameworks with rigid joints such as portal frames, or a combination of the above.

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Oriented strand board This is a panel product made from flakes or large chips of wood at least (OSB) twice as long as they are wide, bonded together with an adhesive under heat and pressure in layers. The directions of the fibres within each layer are generally in the same direction, but in some cases the direction alternates between layers. Its most common structural use is in timber frame walls and prefabricated I-joists.

Parallel strand lumber An alternative to large-section solid timber, PSL consists of strands of (PSL) timber 2mm to 3mm thick and up to 2400mm long cut from peeled log veneers. They are orientated parallel to the finished length, then glued together with a structural adhesive under pressure to form a material superior in strength and stiffness to the wood from which it was made. Par arti ticl cleb eboa oard rd

A pan anel el pro rodu duct ct mad adee fr fro om sm smal alll wo woo od par arti ticl cles es an and d a sy synth thet etic ic res esiin  bonded under heat and pressure. Boards are available in thicknesses from 3 to 50mm. They may be of uniform construction through their thickness, of graded density or of a distinct 3- or 5-layer construction. Commonly called ‘chipboard’, its most common structural use is in flooring.

Party floo floor, r, party wall Generic Generic terms for floor floorss and walls which separate separate dwellings dwellings or areas designated for some other purpose from other dwellings or areas designated for some other different purpose within the same building, or which are required to subdivide a large building for purposes of fire resistance. Party floors are described in the National Building Regulations as compartment or separating floors depending on the function being considered. Perman Per manent ent acti action onss

Dead load Dead loads, s, such such as the the sel self-w f-weig eight ht of the str struct ucture ure or fit fittin tings, gs, anc ancill illari aries es and fixed equipment.

Platform frame construction

A building method based on storey height timber framed and sheathed wall panels which act as vertical load-bearing diaphragms and support roofs and floors acting as horizontal diaphragms.

Plug Pl ug shea shearr failu failure re

A fo form rm of of bloc block k shea shearr fail failur uree in whi which ch the the blo block ck doe doess not not exte extend nd thr throu ough gh the full thickness of the ruptured member. member.

Plywood

A panel product made by gluing together veneers of timber, usually with alternating fibre directions.

Portal frame

A frame in in th the fo form of of a 2- or or 33-pinned arch, de designed to be be st stable in in it its  plane. It is generally used to resist horizontal loads where other bracing methods are not permitted and a large, open space is required. Timber  portals are usually designed as 2-pinned arches, with moment resisting site joints for ease of transportation.

Punched metal plate fastener (PMPF)

A metal plate with integral projections punched out in one direction  perpendicular to the base of the plate, used to join together adjacent softwood members in the same plane. Also called a ‘connector plate’.

PVAc

A polyvinyl acetate (PVA) adhesive with improved properties, often used to provide additional fixity to floor decking.

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Racking

The effect caused by horizontal actions in the plane of a wall. (The racking strength of a wall is the load it can resist applied in the plane of the wall.)

Rais Ra ised ed ti tiee tr trus usss

Someti Some time mess call called ed a ‘c ‘col olla larr trus truss’ s’,, this this is is a tri trian angu gula late ted d roof roof tr trus usss in which the ceiling tie is attached to the rafters at a level above the eaves, normally to provide more headroom.

Resistance

The strength of a member in a particular mode of failure.

Reversible serviceability limit

A serviceability limit state in which the effects of exceeding it disappear when the actions causing it are removed.

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state Rim beam

A beam positioned at at th the ou outer ed edge of of a floor wh which pr provides fu full or or  partial support across across an opening in the case of its accidental removal. In  platform timber frame design a rim beam is usually a solid timber, LVL LVL or prefabricated timber I-joist which is nailed into the ends of joists or  placed parallel to the edge joists and transfers part of the vertical load from a wall to the wall or foundation beneath it.

Rope effect

A contribution ma made to to th the la lateral lo load ca capacity of of a do dowel-type connection by the resistance to axial withdrawal of the fastener when the mode of failure includes bending of the fastener.

Sarked roof

A roof made with sarking.

Sarking

Wood based panels fastened to the upper side of rafters. Sarking may be designed and used as a structural diaphragm.

Separating floor, separating wall

A floor or wall which separates dwellings or areas designated for some other purpose from other dwellings or areas designated for some other different purpose within the same building. (The use of the term in  National Building Regulations is not always consistent.)

Serviceability limit states

Limit states beyond which specified service criteria are no longer met.

Service class

Refer to Section 2.15.

Shear plane

A plane between two connec ectted members which are load adeed in different directions. A dowel dowel connecting 5 members loaded in alternate directions would have 4 shear planes.

Shear plate

A timber co connector co consisting of of a ci circular pl plate fl flanged on on on one si side and with a central bolt hole, which is fitted into a recess in the face of a connected timber member.

Structural Insulated Panel System (SIPS)

A SIPS panel consists of two wood-based panels with a rigid insulating foam plastic-based core between them. They are laminated together to  produce a one-piece structural building system which can be used to form whole wall, roof or floor components.

SLS

Abbreviation for Serviceability limit state.

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Softwood

Solid coniferous timber, widely used for beams and columns with low or medium loading, in the manufacture of glulam, LVL, OSB, plywood and  particleboard, for cladding cladding and joinery joinery,, and for the flanges flanges of some types types of prefabricated timber joist. Softwoods generally require preservative treatment for external structural use.

Slip

The relative movement between two loaded members within the area of a mechanically fastened connection between them.

Slip modulus

A property us used to to cal calcu cullate th the re relative mo movement be between tw two connected members of a structure, expressed in N/mm. For a laterally loaded dowelled connection the slip modulus allows for deformation in the fastener and the members on both sides of the shear plane.

Space st structures

Domes, gr grid shells, et etc.

Spandrel

The triangular area of a gable wall between the eaves and the ridge.

Splice plate

A plate, usually of steel or plywood, fas fastten eneed to two or more timber members to join them end-to-end or at a node.

Split ring

A timber connector consisting of a steel ring which is fitted into circular grooves cut into adjacent faces of connected timber members.

Stress Str essed ed ski skin n pan panel el

Term ermed ed a ‘thin ‘thin-fl -flang anged ed beam’ beam’ in EC5, EC5, a timbe timberr stresse stressed d skin skin panel panel can  be described as a set of parallel I-joists of which the flanges are made of a wood-based panel product and the webs of solid timber or possibly an STC, with the flange material continuous across the joists. The connection between the flanges and webs may be made by means of mechanical fasteners (generally nails or screws) or adhesive bonding. When mechanical fasteners are used, joint slip must be allowed for in calculating the composite strength and stiffness of the panel.

Structural timber composites

Also known as ‘engineered wood products’, glulam, LSL, LVL, PSL are efficient replacements for large sections se ctions of solid timber timber..

STCs

See ‘Structural timber composites’.

Stud St ud,, wal walll stu stud d

A ve vert rtic ical ally ly or orie ient ntat ated ed so soli lid d tim timbe berr or or eng engin inee eere red d woo wood d pr prod oduc uctt mem membe berr which resists vertical loads and wind loads within a timber wall. In structurally sheathed wall panels a full height wall stud also transfers  panel shear forces to the foundation.

Syst Sy stem em st stre reng ngth th

The capa The capaci city ty of a tim timbe berr stru struct ctur uree cons consis isti ting ng of sev sever eral al equ equal ally ly spa space ced d similar members, components or assemblies acting together to resist load. Since wood based members even of the same grade vary in their  properties, it may be assumed that that when several of them act together they they do not all have the minimum characteristic strength properties which would have to be used if they acted alone. The weaker members are less stiff and therefore attract less load than the stronger members. Their combined strength is therefore greater than the sum of their individual strengths, and this is allowed for by a system factor in the Code.

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T&G

See ‘Tongue and groove’.

Target size

The specified size (breadth an and d depth or len eng gth) of timber at a reference moisture content, to which permissible deviations are related. Target sizes are used for engineering design calculations, even though the actual size depends on the moisture content (see Section 3.3.2.3).

Timb imber er con connec nector torss

Toot oothed hed plat plates, es, spli splitt rings, rings, shea shearr plate platess or simi similar lar devi devices ces used used in in conjunction with a bolt to transfer shear loads between adjacent timber members.

Timber frame construction

A building method or a building in which the load-bearing walls are made of a rectangular timber framework sheathed with a wood-based  panel product or gypsum plasterboard. The external walls are invariably sheathed on the outside with a wood-based panel product, most commonly OSB. The two principal types of timber frame construction are balloon frame and platform frame, the latter type being nearly always used in the UK.

Tol oler eran ance ce cl clas asss

A se sett of of per permi mitt tted ed di dime mens nsio iona nall dev devia iati tion onss fro from m the the ta tarrge gett siz sizee at at the the reference moisture content.

Tong ongue ue and and groove groove

The edg edgee of a sol solid id timb timber er boar board d or woo wood-b d-base ased d board board pro profil filed ed in in such such a way that adjacent boards can be locked together. A tongue in one board fits into a groove in its neighbour neighbour.. This keeps adjacent boards in line and enables them to share loads.

Toot oth hed pla late te

A ro roun und d or or sq squar aree ti timbe berr con conn nec ecto torr mad madee of of sh shee eett ste steel el wi with th tri rian angu gula larr teeth projecting at right angles around its circumference on one or both sides. The teeth are embedded into the connected timber member or members, normally by the use of a high tensile steel bolt and nut.

Tru russ ssed ed raf raftter

A st stru ruct ctur ural al as asse sem mbly of ti tim mber mem embe bers rs of the the sa sam me th thic ick kne ness ss,, fas faste ten ned together in one plane by metal plate fasteners or plywood gussets for the support of roofs and ceilings. Trussed rafters are used at spacings of 400mm to 600mm and are generally made with softwood and punched metal plate fasteners.

Var aria iabl blee ac acti tion onss

Var aria iabl blee act actio ions ns ar aree act actio ions ns wh whic ich h var vary y in in mag magni nitu tude de wi with th ti time me.. Th They ey mainly comprise imposed loads, snow loads and wind loads.

ULS

Abbreviation for Ultimate limit state.

Ultimate Ultim ate limi limitt states states

Limit states Limit states associated associated with collap collapse se or other form formss of struc structural tural failu failure re that may endanger the safety of people.

Unfavoura Unfav ourable ble effe effect ct

An undesi undesirable rable struc structural tural effe effect ct on a structu structural ral member member,, compon component ent or or assembly, normally produced by an action.

Woo ood d par parti ticl cleb eboa oard rd

Seee ‘Par Se ‘Parti ticl cleb eboa oard rd’. ’.

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Notation Latin uppe r c ase letters  A  Ad   E   E 0,05 0,05  E 0,mean 0,mean  E 90,mean 90,mean  E ct,0,mean ct,0,mean

Cross-sectional area; Accidental action Design value of accidental action The effect of an action – e.g. bending moment, deflection Fifth percentile value of modulus of elasticity Mean value of modulus of elasticity parallel to grain (or parallel to surface grain of  plywood or OSB) Mean value of modulus of elasticity perpendicular to surface grain of plywood or OSB Mean value of modulus of elasticity in compression and tension parallel to surface grain of plywood or OSB

 E ct,90,mean Mean value of modulus of elasticity in compression and tension perpendicular to surface grain of plywood or OSB  E mean Mean value of modulus of elasticity mean  E mean,fin Final mean value of modulus of elasticity mean,fin F   Force or action; Point load  F d d  Design value of a force or point load 

Ff,Rd F i,t,Ed i,t,Ed F i,vert,Ed i,vert,Ed F i,v,Rd i,v,Rd F t  F v,Ed v,Ed

Design load capacity per fastener in wall diaphragm Design tensile reaction force at end of shear wall Design vertical load on wall Design racking resistance of wall i (in Section 10.8.1.1) Tensile force Design shear force per shear plane of fastener; Horizontal design effect on wall

F v,Rd v,Rd F v,Rk v,Rk G Gk,j Gmean Gr,mean Gv,mean  H   K ser  ser   K ser,fin ser,fin K u 

diaphragm Design load capacity per shear plane per fastener; Design racking load capacity Characteristic load capacity per shear plane per fastener  Permanent action Characteristic value of a permanent action, numbered  j Mean value of shear modulus (in panel shear for panel products) Mean planar shear modulus in bending for panel products Mean planar shear modulus in racking for panel products (same as Gmean) Overall rise of a truss Slip modulus Final slip modulus Instantaneous slip modulus for ultimate limit states

 M d    M y,Rk y,Rk  N   Q Qk,1

Design moment Characteristic yield moment of fastener  Axial force Variable action Characteristic value of a leading variable action

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Qk,i  Rd  

Characteristic value of a variable action, numbered i Design value of a load capacity

 Rk   V   W y   X d d    X k k  

Characteristic load capacity Shear force Section modulus about axis y Design value of a strength property Characteristic value of a strength property

Latin low lowe e r c a se le le tt tte e rs a a1  a2  a3,c a3,t a4,c

Distance Spacing, parallel to grain, of fasteners within one row Spacing, perpendicular to grain, between rows of fasteners Distance, parallel to grain, between fastener and unloaded end  Distance, parallel to grain, between fastener and loaded end  Distance, perpendicular to grain, between fastener and unloaded edge

a4,t b  bi bnet d   d 0 d char,n char,n d ef ef

Distance, perpendicular to grain, between fastener and loaded edge Width Width of wall i (in Section 10.8.1.1) Clear distance between studs Diameter  Charring depth parameter   Notional charring depth Effective diameter; Effective charring depth

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 f c,90,k c,90,k

Design compressive strength parallel to grain (or surface grain of plywood or OSB) Characteristic compressive strength parallel to grain (or surface grain of plywood or OSB) Characteristic compressive strength perpendicular to grain (or surface grain of

 f h,k h,k  f 1   f m,k m,k  f m,0,k m,0,k  f m,90,k m,90,k  f m,y,d m,y,d  f m,z,d m,z,d  f t,0,d t,0,d  f t,0,k t,0,k  f t,90,d t,90,d  f t,90,k t,90,k

 plywood or OSB) Characteristic embedment strength Fundamental frequency Characteristic bending strength Characteristic bending strength parallel to surface grain of plywood or OSB Characteristic bending strength perpendicular to surface grain of plywood or OSB Design bending strength about the major  y-axis Design bending strength about the minor z-axis Design tensile strength parallel to grain (or surface grain of plywood or OSB) Characteristic tensile strength parallel to grain (or surface grain of plywood or OSB) Design tensile strength perpendicular to grain (or surface grain of plywood or OSB) Characteristic tensile strength perpendicular to grain (or surface grain of plywood or

 f c,0,d c,0,d  f c,0,k c,0,k

 f v,0,k  v,0,k   f v,90,k  v,90,k 

OSB) Characteristic transverse shear strength in bending parallel to surface grain of plywood or OSB Characteristic transverse shear strength in bending perpendicular to the surface grain of plywood or OSB

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 f v,d v,d  f v,k  v,k   f v,r,k v,r,k

Design shear strength (panel shear in panel products) Characteristic shear strength (panel shear in panel products) Characteristic rolling shear strength in plywood 

g Distributed permanent load  h  Depth of member; Height of wall he Distance between loaded edge and centre of most distant fastener  hef Effective depth k 0 Charring coefficient k  bond  Glued bonding pressure factor  k c,y c,y or k c,z c,z Instability factor  Factor used for lateral buckling k crit crit k d Dimension factor for panel k def Deformation factor, dependent on duration of load and moisture content def k h Depth or width factor  k c,90 Bearing strength modification factor  c,90 dist k dist k  joint k m k masonry masonry k mc mc k mod  mod  k n  k shear  shear  k sys sys k v

Proportion of point load acting on a single joist Deformation factor for connections Factor to allow for the re-distribution of bending stresses in a cross-section Factor to allow for the wind shielding effect of masonry walls Glued bond moisture effect factor  Strength modification factor for duration of load and moisture content Material factor for notched beams Amplification factor to account for shear deflections in vibration calculations System strength factor  Reduction factor for notched beams Span

l lef 

Effective length

m  nef  p  q qi  s  s0  t   t  pen u ucreep ufin

Mass per unit area Effective number of fasteners in a row parallel to grain Distributed load  Distributed variable load  Equivalent uniformly distributed load  Spacing; Size effect parameter  Basic fastener spacing Thickness Penetration depth Deformation – slip or horizontal horizontal deflection Creep deformation Final deformation

uinst uinst,j uinst,Q,1 uinst,Q,i

Instantaneous deformation Instantaneous deformation for a permanent action G j Instantaneous deformation for the leading variable action Q1 Instantaneous deformation for accompanying variable actions Qi

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wcreep wfin winst,G winst,Q wnet,fin

Creep deflection Final deflection Instantaneous deflection for a permanent action, G Instantaneous deflection for a variable action, Q  Net final deflection

G ree k lowe lowe r c ase lett letters ers a

Angle (‘alpha’)

c

Partial factor (‘gamma’)

cG

Partial factor for permanent actions

cG,j

Partial factor for permanent action  j

cM  cQ

Partial factor for material properties, also accounting for model uncertainties and dimensional variations Partial factor for variable actions

cQ,i

Partial factor for variable action i

y my

Poisson’s ratio (‘nu’) Slenderness ratio corresponding to bending about the y-axis (‘lambda’)

mz

Slenderness ratio corresponding to bending about the z-axis

mrel,y

Relative slenderness ratio corresponding to bending about the  y-axis

mrel,z

Relative slenderness ratio corresponding to bending about the  z-axis

tk 

Characteristic density (normally a fifth percentile of the density) (‘rho’)

tmean

Mean density

vc,0,d 

Design compressive stress parallel to grain (‘sigma’)

vm,crit

Critical bending stress

vm,y,d 

Design bending stress about the major  y-axis

vm,z,d 

Design bending stress about the minor  z-axis

vt,0,d 

Design tensile stress parallel to grain

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vt,90,d 

Design tensile stress perpendicular to grain

xd 

Design shear stress (‘tau’)

p

Reduction factor (‘xi’)

z

Diameter (‘phi’)

}0

Factor for combination value of a variable action (‘psi’)

}1

Factor for frequent value of a variable action

}2

Factor for quasi-permanent value of a variable action

g

Modal damping ratio (‘zeta’)

 Note that ‘ f ’ denotes a material property and ‘v‘ or ‘x‘ a stress.

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Foreword

The Eurocode for the Design of Timber Structures (EC5) comprising BS EN 1995-1-1: General: Common rules and rules for buildings   was published in December 2004. The UK National Annex (NA) setting out the Nationally Determined Parameters (NDPs) has also been published. These documents, together with previously published documents BS EN 1990:  Basis of Structural Design  and BS EN 1991:  Actions on Structures and their respective NAs, provide a suite of information for the design of most types of timber  building structures in the UK. After a period period of co-existence, the current National National Standards will be withdrawn and replaced by the Eurocodes. The Institution of Structural Engineers has not previously published a manual for the design of timber structures. This Manual follows the basic format of manuals published  by the Institution for other structural materials. It provides guidance on the design of structures of single-storey and medium-rise multi-storey buildings using common forms of structural timberwork. Structures designed in accordance with this  Manual will normally comply with EC5. However it is not intended to be a substitute for the greater potential range of EC5. The NDPs from the UK NA have been taken into account in the design formulae that are presented. Timber Timb er is a relatively complex structural material therefore a manual for the design of timber structures is bound to be more extensive than that for other materials. Despite its length, designers should find this  Manual  concise and useful in practical design. It is laid out for hand calculation, but the procedures are equally suitable for spread sheet and/or computer application. An example is in the design of connections; EC5 requires the solution of a series of expressions, a process that is not practicable in hand calculations and so tabulated values are provided in the  Manual. The accompanying CD provides connection design software and more extensive material properties. The Timber Engineering community in the UK is small but through those directly associated with the  Manual’  Manual’ss preparation we were able to draw on a wealth of knowledge. EC5 is a design code on the European model; it contains many design rules but little

 practical advice. Throughout Throughout the preparation preparation of the Manual, we have been conscious of the need to capture practical knowledge and set it down. We We have worked hard to interpret the intent of the Eurocode and where appropriate due to Eurocode limitations we have used alternative methods. Special thanks are due to Arnold Page who researched and drafted the  Manual. Through his participation, we were fortunate to have been able to draw on information from both TRADA’s knowledge base, built up over 70 years, as well as Arnold’s own deep understanding gained over half a lifetime in timber engineering. The  Manual  was more demanding and time consuming than originally envisaged and particular thanks are due to TRADA for recognising the importance of the  Manual to the construction industry and continuing to fund Arnold’s Arnold’s time to enable a proper completion.

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Special thanks are also due to all of the members of the Task Group and to their organisations, who have given their time voluntarily. I am also grateful to Ben Cresswell Riol for acting as secretary to the Group and for having undertaken this with patience and skill. During the review process, members of the Institution provided a substantial response, both in quantity and quality on the draft  Manual, which has contributed to its improvement and completion. I join with all of the other members of the Task Group in commending this Manual  to the construction industry.

R J L Harris Chairman  

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1 Introd oduc ucttion

1.1

Aims of the M  Ma a nua l

 Manual and the accompanying CD provides qualified Structural Engineers with guidance This on the structural design of single-storey and medium-rise multi-storey buildings using common forms of structural timberwork. Structures designed in accordance with the Manual will normally comply with BS EN 1995-1-1:  Eurocode 5: Design of timber structures – Part 1-1: General: Common rules and rules for buildings  (EC5)1, together with its supporting codes and standards. The  Manual  is primarily intended for carrying out simple calculations, and is not necessarily relevantt to the design of complex relevan c omplex buildings requirin requiring g more sophisti sophisticated cated analysis. analysis. However However it is good good  practi  pra ctice ce to che check ck the the outpu outputt of com comple plex x analy analyses ses usin using g simpl simplifi ified ed meth methods ods suc such h as thos thosee provid provided. ed. For simplicity reference to clauses in BS EN 1995-1-1 will be in the form ‘EC5 4.2(1)’ Reference to clauses in the  Manual will be by section, e.g. ‘Section 2.1.1’.

1.2

The Eur uroc oco ode sys systtem

1.2.1 1.2. 1 O rig in a nd p ur urp p o se The structural Eurocodes are produced by the European Committee for Standardisation (CEN), its members being the national standards bodies of the EU and EFTA countries, e.g. BSI. 1.2.2 List o f Euroc o d e s 1.2.2 The complete set of Eurocodes consists of the following: BS EN 1990: Eurocode: Basis of structural design (EC0) BS EN 1991: Eurocode 1: Actions on structures (EC1)   Part 1-1: General actions – Densities, self-weight and imposed loads   Part 1-2: General actions on structures exposed to fire   Part 1-3: General actions – Snow loads   Part 1-4: General actions – Wind loads   Part 1-5: General actions – Thermal actions Part 1-6: Actions during execution   Part 1-7: Accidental actions from impact and explosions   Part 2: Traffic Traf fic loads on bridges   Part 3: Actions induced by cranes and machinery   Part 4: Actions in silos and tanks BS EN 1992: Eurocode 2: Design of concrete structures (EC2) BS EN 1993: Eurocode 3: Design of steel structures (EC3) BS EN 1994: Eurocode 4: Design of composite steel and concrete structures (EC4)

BS EN 1995: Eurocode 5: Design of timber structures   Part 1-1: General – Common rules and rules for building (EC5)   Part 1-2: General – Structural fire design (EC5-1-2)   Part 2: Bridges (EC5-2)

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BS EN 1996: Eurocode 6: Design of masonry structures BS EN 1997: Eurocode 7: Geotechnical design BS EN 1998: Eurocode 8: Design of structures for earthquake resistance BS EN 1999: Eurocode 9: Design of aluminium structures Eurocodes 1 to 9 all comprise several parts, but only EC1 and EC5 have been listed in full. 1.2.3 Pri 1.2.3 Princ ip le s a nd Ap Ap p lic a ti tio o n Rul ulee s All the Eurocodes contain ‘Principles’ and ‘Application Rules’.  Principles are general statements, definitions, design rules or analytical models for which no alternative is permitted, for example EC5 8.2.3(2)P “The strength of the steel plate shall be checked.” Clauses which comprise a principle are identified by the letter ‘P’. Application Rules are generally recognised rules which comply with and satisfy the Principles. Alternative design rules may be used instead, provided that they can be demonstrated to comply with the Principles and to produce similar levels of safety, serviceability and durability to the Application Rules. 1.2. 1. 2.4 4

Na ti tio o na l Anne xe s

Every National Standards body may produce its own National Annex (NA) for each part of each Eurocode. An NA provides values or decisions related to ‘Nationally Determined Parameters’ (NDPs) which allow for differences in such matters as climatic conditions, standards of workmanship, and perceptions of acceptability in deflections. UK NDPs are identified by bold type in the  Manua  Manuall. 1.2.5 1.2. 5 Non c o ntr ntraa d ic tor tory y c om p le m e nta ry inf nforma orma ti tio on The Eurocode system also permits reference in NAs to sources of ‘non contradictory complementary information’ (NCCI) which help designers to use the associated Eurocodes. In the UK the principal source for EC5 is BS PD 6693 2. This Manual includes a number of NCCI items which will not be found in EC5 itself.

1.2.6 1.2. 6 Eur uro o c o d e d e sig n b a sis The Eurocode common basis of design for all structural materials is based on limit states and  partial safety factors. For structural s tructural timber design in the UK this represents a major change from BS 5268-23, in which all the safety factors are incorporated in the permissible stresses. A limit state is simply a state beyond which a structure no longer satisfies its performance requirements. Ultimate limit states are associated with collapse or similar forms of structural failure that may endanger the safety of people, and generally involve the consideration of strength and stability. Serviceability limit states are associated with user discomfort or dissatisfaction or a lack of functionality, and generally involve the consideration of deformation (i.e. the deflections of members or slip in connections). Partial safety factors are used to increase the values of loads and to decrease the material strength values (also to adjust stiffness properties for second order linear

1

elastic analysis – see EC5 2.2.2(1) Note 2). In each case the values of the factors are specified

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and are applied to the characteristic values of the loads or material properties, so the approach to safety is known and transparent.

1.3

Sc op ope e of the M  Man anua ua l

1.3.1 1.3. 1 Na ti tio o na l sc o p e The Manual is intended primarily for the design of buildings within the United Kingdom. Where values and design methods specified in UK National Annexes are quoted the information given may not be applicable elsewhere. 1.3.2 1.3. 2 Str truc uc tur turee s c o ve re d For the majority of design situations and a nd materials involving timber the information required has  been provided in this  Manual or in the accompanying CD. Two principal types of timber structure are covered: • open frame buildings, i.e.  –  statically determinate beams and columns stabilised by bracing and/or vertical and horizontal diaphragms  –  frameworks with rigid joints such as portal frames  –  a combination of the above • timber platform frame buildings with a maximum height of 18 metres to the finished floor level of the top storey. 1.3.3 1.3. 3 • • • • •

Princ ip a l sub je c ts c o ve re d Pri roofs, floors and walls flexural, tension and compression members diaphragms, flitch beams mechanically fastened and glued connections load duration, service class, creep, durability and fire resistance.

1.3.4 1.3. 4 •

Sub je c ts no t c o ve re d foundations and geotechnical design (see BS EN 1997: Eurocode 7: Geotechnical design   (EC7)4)

•

seismic design (see BS EN 1998:  Eurocode 8: Design of structures for earthquake resistance (EC8)5) the following detailed design issues:  –  analysis of frame structures – EC5 5.4.2  –  analysis of trusses with punched metal plate fasteners – EC5 5.4.3  –  glued thin-webbed beams – EC5 9.1.1  –  glued thin-flanged beams – EC5 9.1.2  –  mechanically jointed beams – EC5 9.1.3  –  mechanically jointed and glued columns – EC5 9.1.4  –  trusses – EC5 9.2.1 and 9.2.2.

•

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1.3. 1. 3.5 5 •

•

•

Ad d iti tio o na l inf nfo o rm a ti tio o n c o nta ine d in in the C D material properties of solid timber, glulam, wood-based panel products and structural timber composites nail, screw, bolt and dowel connection spreadsheets links to manufacturers web sites.

For a more detailed list see the Contents. 1. 1.3. 3.6 6 So ur urcc e s o f a d d iti tio o na l informa ti tio on For timber-related subjects which are not covered by the  Manual, EC5 or its supporting standards should be consulted. Other useful publications are: STEP Timber Engineering, Volumes 1 and 2 6 TRADA’s TRADA ’s EC5 Guidance Documents and EC5 Design Examples7 TRADA’s TRADA ’s Software Softwar e Toolbox8 (includes the design of connections to EC5 and will include domestic timber members in the near future) Panel Guide Partnership’s Partnership’s PanelGuide9 Building Research Establishment published material. •

•

•

•

•

It is also intended to publish other manuals in this series on EC0 and EC1. Further sources of information are given in the References. 1.4

C ontents of the  M  Man anua uall

The  Manual is set out in the sequence normally followed in design. Sections 2, 3 Principles of structural timber design   Section 4 Initial building design process   Sections 5, 6 Design of individual members and connections   Sections 7-10 Design of roofs, floors and two principal types of building There are two additional sections.   Section 11 Checking and specification guidance  

Section 12

Workmanship, installation, control and maintenance

1.5

Definitio ions ns

1.5.1 1.5. 1 Te c hn ic a l te rm s In order to rationalise the meanings of various technical terms for easy translation, some of the terms used in the past have been redefined more precisely in the Eurocodes. Those of particular importance are listed, together with other timber related terms which may not be familiar to engineers who are more accustomed to other materials, in the glossary.

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Am e n d m e n t s – Ma y 2 00 00 8

3

 

1.5.2 Ax 1.5.2 Axiis no m e nc la tur turee The use of traditional axis nomenclature in the UK has been altered to match a consistent European approach throughout throughout the Eurocodes, as shown in Figure 1.1. The x-x axis lies along the length of the member member,,  y-y is the principal or major axis, and  z -z  is the minor axis.

 z

 y  x

x  y

 z

Fig 1.1  1.6

No m e n c la t ur u re o f a xe s

Notation

The Latin and Greek characters that apply to designs to EC5 are listed under Notation in the  preliminary pages of this  Manual.

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5

2 Gener enera al pr prin inc c iples

2.1

Basis of de design sign

2.1.1 2.1. 1 Ba sic re q ui uirre m e nts BS EN 1990:  Eurocode: Basis of Structural design (EC0)10 requires structures to be designed so that, within specified limits, they are safe, serviceable, robust and durable. It is a legal requirement that building designs conform to the requirements of the applicable Building Regulations in force at the time. House-building guarantors may impose additional requirements on structural design. 2.1. 2. 1.2 2

De sig n c od e s

 2.1.2.1  2.1. 2.1 Struc tura turall Euro Eurocc od e s Structural designs carried out in accordance with EC5 must be based on the design principles set out in EC0, and on the imposed loads specified in the various parts of BS EN 1991:  Eurocode 1: Actions on Structures  (EC1). Unless more accurate values are known, the material weights specified in BS EN 1991-1-1:  Actions on Structures. General actions. Densities, self-weight, imposed loads for buildings. (EC1-1-1)11 should be used. Reference should be made to the National Annexes to these codes for the values of Nationally Determined Parameters, and to supporting European standards for material properties, dimensions, tolerances and other information which are required to complete a structural design. EC0 5.2 also allows design assisted by testing in cases where reliable modelling is difficult, large numbers of similar components are to be made, or to verify design assumptions.

 2.1.2.2  2.1. 2.2 •

•

• •

•

6

D iffe iffere renc nc e s betwe be twe e n BS 5268 and an d EC 5 The two codes have different definitions of duration of loads. BS 5268 has long term, medium term, short term and very short term; whereas EC5 has permanent, long term, medium term, short term and instantaneous. It follows that a particular action will fall into different load duration categories in the two codes. For example snow loading is mediumterm in BS 5268 but it is short-term in EC5 (see Table 2.2). BS 5268 grade values of strength properties are safe for all load durations, but the values used with EC5 are characteristic test values which must be reduced for the appropriate load duration and by a safety factor. The stiffness moduli for solid timber strength classes given in BS 5268 differ from those in BS EN 33812. EC5 fastener load capacities derived from calculations or tables yield Eurocode design values which are significantly higher than the permissible values obtained from the tables in BS 5268, so they must not be used in conjunction with the unfactored loads. EC5 requires creep effects to be considered in calculating deflections, and some of the recommended limits on deflection, e.g. in the National Annex, refer to final not initial deflections.

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Where EC5 does not provide necessary information it is acceptable to use information from other design codes provided that it is compatible with the Eurocode safety format and does not conflict

with EC5. 2.1.3 2.1. 3 Str truc uc tur turaa l m a te ria ls c o m p lia nc e All products specified for structural use in Europe must satisfy the requirements of the Construction Products Directive. This means that solid timber should be structurally graded to a standard listed in BS EN 14081-113 and stamped accordingly by a certified timber grading agency. In all but the three European States listed below, glulam, wood-based panel products and other proprietary wood-based products may be specified only if they have been certified  by a Notified Body or declared as fit for purpose by a manufacturer manufacturer,, in accordance with the relevant harmonised European standard or European Technical Approval. Such products will have associated literature detailing the relevant technical specification which they meet, and they may in addition carry a ‘CE’ mark with a summary of this information. The certification literature will include the characteristic material properties and any associated modification factors which should be used for structural calculations. In the UK, Ireland and Sweden alternative methods of demonstrating compliance with the Directive are permitted for these products via third party certification from notified bodies. Products certified by such alternative methods may be specified in designs to EC5 but they may not be used in any structures which will be erected in European countries other than the three mentioned above. However they should not be specified unless the certification literature includes either characteristic material properties derived in accordance with standard European test methods or BS 5268-23 grade values in the case of wood-based panel products (for which a conversion procedure is available (see Section 3.3.3)). For further information on certification, contact the Timber Trades Federation for solid timber, the Glued Laminated Timber Association for glulam, or the Wood Panel Industries Federation for wood-based panel products, contact details for whom may be found in Appendix B.

2.2

Respo sponsibilit nsibility y for de design sign

The Engineer has overall responsibility for ensuring that the strength, stability and structural serviceability of a building and its elements will, if properly constructed, maintained and used for its intended purpose, meet the requirements of the client and the relevant Building Regulations. The Engineer also has a duty of care concerning durability. durability. This is principally a matter of suitable architectural detailing but it may sometimes require the specification of preservative or  protective treatments for timber materials and metal fastenings. While the Engineer’s work is concerned primarily with the adequacy of load-bearing members, components and assemblies, it might also include non load-bearing items where the integrity of their fixing has safety implications, e.g. the attachment of external cladding.

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2.3 2.3

Buil uilding ding us use e and loc loca ation

The designated use and geographical location of the building should be specified. This will determine the variable actions, requirements for resistance to disproportionate collapse, requirements for the corrosion protection of metal fasteners, and in certain limited areas the necessity for the protective treatment of roof timbers against house longhorn beetle.

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2.4

Design life

A design life for the building should be specified (EC0 2.3). A properly properly designed and maintained timber building can last for centuries, but EC0 suggests a design life of 50 years for building structures, and that has been assumed in this  Manual. For temporary structures EC0 suggests a 10 year design life, and where there is no risk that this period may be exceeded the assumption of 10 years will permit the use of higher strength properties and lower creep factors.

2.5

Design situa uattions

The building must be designed to have adequate strength, stability and structural serviceability in the following situations: • during construction (the execution phase) • in designated use throughout its design life (see Section 2.4) • in accidental design events. If any significant seismic actions on the building are likely to occur within the design life then EC8 should be consulted.

2.6

Stability

Overall stability checks are particularly important for timber structures because they are relatively light in weight. The structure should resist uplift, sliding and overturning forces produced by the wind, both during the execution phase and in the finished structure. Particular care should be taken when the height:breadth ratio of a timber building exceeds 2:1. For individual members and assemblies EC5 9.2.5.1 states three principles. • Structures which are not otherwise stiff must be braced to prevent instability and excessive deflection. • Stresses caused by geometrical and structural imperfections and by induced deflections, e.g. from joint slip, must be taken into account. • The required bracing forces should be determined on the basis of the most unfavourable combination of structural imperfections and induced deflections. For methods of providing stability see Section 5.7.

2.7

Construc Const ucttion

The resistance of a timber building to overturning or sliding normally takes into account the weight of the roof, but this will not be present during the construction phases. Similarly the resistance of timber frame buildings to horizontal wind forces may depend on the connection of the roof to an adjoining terrace of houses, or on the shielding effect of brick cladding, neither of

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which will be present during construction. BS EN 1991-1-4:  Eurocode 1: Actions on structures: General actions. Wind loads (EC1-1-4)14 allows a reduction in wind loads for the execution phase,  but the structural adequacy during this period must nevertheless be verified. Where necessary consideration should be given to the need for temporary bracing during the execution phase. To comply with the Construction (Design and Management) Regulations 15 the Engineer should consider and where necessary provide safe procedures or instructions for: • manual handling • the method of erection • the type of craneage

•

lifting points.

The Engineer should ensure that this information is recorded in the construction phase plan and the health and safety file. Where design assumptions dictate certain methods and sequences of erection, full information concerning them should be included in the health and safety plan as well as being shown on the design drawings.

2.8

Movement

2.8.1 2.8. 1 Mo istur turee m o ve m e nt The moisture content of timber varies with temperature and humidity. While its dimensions are relatively stable along the grain, across the grain timber swells or shrinks as its moisture content increases or decreases, changing by about 1% for every 5% change in moisture content. Kiln dried structural graded softwood can have a moisture content of 18% to 20% on delivery, and will dry out in a heated environment to 10% to 15%, so its dimensions across the grain may decrease by 1% to 2%. Engineered wood products have either less timber content (e.g. metal web joists) or are delivered to site at a much lower moisture content and are therefore less susceptible to shrinkage. It is also possible to specify ‘super-dried’ solid timber which is delivered at a moisture content of 14% or less and has a moisture resistant coating, significantly reducing cross grain movement  particularly in timber floor joists. Some structural timber composites are also manufactured with water resistant coatings, and if necessary such coatings may be specified both for structural timber composites and for glulam. However none of these materials will retain its dimensions if it is exposed on site to the weather for an extensive period. Particular care is needed in the case of large diaphragms made with wood based panel products (see Table 12.1 and Section 4.5 of Panel Guide Partnership’s PanelGuide9). Where large timber buildings such as sports halls are likely to take a long time to erect it may be advisable to consider a temporary roofed area for stored materials. 2.8.2 2.8. 2 The rma l m ove m e nt It is rarely necessary to consider thermal movement in timber structures. The linear coefficient of thermal expansion of timber along the grain (about 3.5 #10-6 per ºC) is smaller than that of steel or concrete, and its greater elasticity enables it to accommodate movement more easily. Across the grain the coefficient ranges from 26 #10-6 to 35#10-6 per °C, but any increase in dimension

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due to temperature is more than counteracted by shrinkage due to the reduced moisture content. Also timber’s thermal conductivity is much lower than that of steel, so its temperature is less responsive to ambient changes in temperature. 2.8.3 2.8. 3 Di Difffe re nti ntiaa l m o ve m e nt Differential movement in timber frame buildings is covered in Section 10.11. 2.8.4 2.8. 4 Move m e nt jo ints Movement joints to accommodate thermal and moisture movements in a timber structure are rarely required. Movement joints in claddings are required as in non-timber buildings. For the spacing of expansion gaps in wood based horizontal diaphragms refer to Table 12.1.

9

2.9

Creep

For SLS calculations creep in the deflection of loaded members and creep in the slip between mechanically connected members should be included whenever final values are relevant. For ULS design situations creep in the deflection of members and in the slip of connections should  be allowed for in the analysis of structures if such deformations cause a significant redistribution of forces and moments.

2.10 2.1 0

Rob obus usttness and dispr disprop oport ortiona ionatte c olla ollapse pse

2.10.1 Ro b ust c o nstr 2.10.1 nstruc uc ti tio on Timber structures, like those made of other materials, must be sufficiently robust in accidental situations to ensure that the loss of individual members or components does not cause the disproportionate collapse of the entire structure or large parts of it (EC0 2.1(4)P). Any damage due, for example, to explosion, impact or the consequences of human error should not be disproportionate to the original cause. Procedures for meeting these requirements are given in Section 5.11. Designing a robust structure also involves: • consideration of how it will be used and the possible consequences – for example flour mills and chemical plants may pose specific problems with regard to explosion and  pressure venting • consideration of construction procedures – for example the ability to make the designed connections properly •  provision of access for routine maintenance and inspection. 2.10..2 Ac 2.10 Ac c id e nta l a c ti tio o ns Where relevant the magnitude of an accidental action for a specific occurrence may be agreed  between the client and the the designer. designer. The design value value of accidental actions, including including exceptional snow drifts, is calculated in accordance with Section 3.2.1.3.

2.11

Fire resistanc nce e

The design should satisfy requirements in the relevant Building Regulations for the particular  building type.

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Depending on their function, members, components and assemblies exposed to fire may  be required to provide one or more of the following for a specified period: • mechanical resistance – they should remain sufficiently strong and stiff to permit a safe exit from the building • integrity – they should form an effective barrier to smoke and flame • insulation – they should limit the transfer of heat by conduction from an area on fire to another area. In addition there may be requirements to: • limit the thermal radiation from the side unexposed to fire • ensure that the surface spread of flame properties do not unduly endanger the occupants of the building or neighbouring buildings. buildings. Adequate mechanical resistance of structural assemblies and members in fire can be achieved by: • insulating them from heat

•

the use of sacrificial timber.

Structural elements including mechanical fasteners can be insulated from heat by covering them with one or more layers of insulating material of a specified thickness. The most common material for this is gypsum plasterboard, but cork, plywood or other wood-based materials may be used instead. The use of sacrificial timber involves checking that the dimensions of the residual sections of timber members after charring are sufficiently large to support the design loads with acceptable deflections within the specified period of fire resistance. Where necessary the section size can be increased to provide the necessary period of fire resistance. This approach could be used for exposed columns or beams for example, and is applicable to solid timber, glulam, LVL and other structural timber composites, but not to engineered timber joists. In structures designed to EC5 the requirements for fire resistance should be achieved in accordance with the design rules given in EC5-1-2.

2.12 2.1 2

Ac oustic ic,, thermal and air tight ightness ness req equir uireme ement nts

The design should satisfy the requirements of the relevant Building Regulations and house  building guarantors relating to acoustic insulation, thermal insulation and air tightness. Although they may impinge on design, these factors are not essential aspects of structural design and are not addressed in any detail in this  Manual.

2.13

Durability

The building should be designed so that it continues to satisfy all the relevant limit state requirements for its specified design life (see Section 2.4). This is achieved by design details which ensure that all the timber remains dry and well ventilated, and where this cannot be ensured  by specifying durable species or suitable protection treatments for its structural members (see Section 3.4).

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2.14 2.14

Maintena enanc nce e

The Construction (Design and Maintenance) Regulations15 require the Designer to consider risks to the health and safety of persons engaged in the maintenance of the structure, to provide safe means of access to elements needing maintenance, and to provide this information for recording in the health and safety file.

2.15 2. 15

Servi ervic c e c lass

2.15.1 Ef 2.15.1 Effe c t of m o istur turee o n str stree ng th a nd sti tifffne ss An increase in moisture content reduces the strength and stiffness properties of timber and wood based materials and increases the amount of creep that occurs. Designs to EC5 should allow for the effects of moisture on strength and creep, but not on the instantaneous stiffness properties (see Section 2.17). 2.15.2 De fini 2.15.2 niti tio o ns of se rvi vicc e c la sse s Moisture content depends on both temperature and atmospheric humidity. For simplicity the moisture content is related to one of three ‘service classes’ which are defined in Table 2.1.

Table 2.1 2.1 Def Definit inition of ser servic vice e classes classes and exa examples mples

11

Servic ervice e class

Tem emper perat atu ure

Approx oxiimat ate e maximum humidity

EMC a  (%)

1

2 0 °C

65%

12%

Examples Examp les from the the EC5 EC 5 NA

Wa rm ro o fs, in t e rm e d ia t e flo o rs, ti tim m b e r-f -frra m e wa lls  – int in t e rn a l a n d p a rty w a lls

2

2 0 °C

85%

20%

C o ld ro o fs, g ro u n d flo o rs, tim ti m b e r-fra m e wa lls – e xte rna l wa lls, e xte rna l use s whe re m e m b e r is p ro t e c t e d fro m d ire c t w e tti ttin ng

3

C o n d it it io ns n s le a d in in g to t o h ig h e r

> 20 %

Ext e rn r n a l u se se s – fu ll lly e xp o se d

m o ist u re re c o n t e n t s t h a n se rvi vicc e c la ss 2. 2.

Note a

EMC = Ma xim um e q ui uillib rium m o istur turee c o nte nt fo fo r m o st so so ftwo o d s.

2.16

Loa oad d dura durattio ion n

2.16.1 2.16. 1 Ef Effe c t of lo lo a d d ur uraa ti tio o n o n str stre ng th a nd sti tifffne ss An increase in load duration reduces the loads which timber can resist and increases the creep  but not the instantaneous elastic stiffness. Designs to EC5 should allow for these effects (see Section 2.17).

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2.1 2.16.2 6.2 De De fini niti tio o ns o f lo a d d ur uraa ti tio o n c la sse s Load duration classes are defined according to the approximate accumulated duration of characteristic load, as shown in Table 2.2.

Table 2.2 Loa oad d dur dura ation c la lass sses C lass

Definition

Examples from the EC 5 NA and EC 0

P e rm rm a n e nt nt

M o re th t h a n 1 0 y e a rs rs

Se lf lf-w e ig ig ht ht

Lo ng n g -t -t e rm rm

6 m o nt n t h s t o 1 0 y e a rs

Te m p o ra ra ry st ru c tu t u re s Stora g e lo a d ing inc lud ing lo a d ing in lo lo fts Wa te r ta n ks ks

M e d iu iu m -t -t e rm rm

1 w e e k to 6 m o n th s

Im p o se se d flo o r lo a d in in g

Sh o rt -t e rm rm

Le ss ss t h a n o n e we we e k

Sn o w M a in t e n a n c e o r m a n lo lo a d in g o n ro ro o fs Re sid u a l st ru ru c t u re re a ft e r a c c id e n t a l e v e n t

In st a nt n t a ne n e o u s In st a nt n t a ne ne o u s

Win d Im p a c t lo lo a d in g Exp lo si sio on

2.17 2.1 7

Fac tors to allow allow for eff effec ec ts of moistur ure e and and load load dura duration

2.17. 2. 17.1 1 Str tree ng th m o d ific a ti tio o n fa c tor tor,, k mod  mod 

Table 2.3 shows values of k mod   for the most common wood-based materials for the service classes mod  for in which they may be used. For structural fibreboards see EC5 Table 3.1. For PSL, LSL and engineered wood joists consult the manufacturers. For timber which is installed at or near its fibre saturation point, e.g. large timbers with minimum cross-sectional dimension > 100mm and not mod  for service class 3. specially dried, use the value of k mod 

2.17.2 2.17. 2 De fo rm a ti tio o n m o d ific a ti tio o n fa fa c to r, k def  def  Table 2.4 shows value val ue of k def   for the most common wood-based materials. For structural fibreboards def  for see EC5 Table 3.2. For PSL, LSL and engineered wood joists consult the manufacturers. For timber which is installed at or near its fibre saturation point, e.g. large timbers with minimum cross-sectional dimension > 100mm and not specially dried, and which is likely to dry out under load, the value of k def   should be increased by 1.00. def  should

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Table 2.3 Va Values lues of k mod  (from om EC5 EC5 Table 3.1) mod  (fr Material

Standards

So lid ti tim m b e r BS EN 1408114081-1 1 13 G lu la m BS EN 1 4 0 8 0 16 LVL BS EN 1 4 3 7 4 17 BS EN 14279 18 P lyw o o d

O SB

Pa rti ticc le  b o a rd

BS EN 6 3 6 19 Pa rt s 1 , 2 a n d 3 Pa rt s 2 a n d 3 Pa rt 3 BS EN 3 0 0 20 O SB/ 2 O SB/ 3 , O SB/ 4 O SB/ 3 , O SB/ 4 BS EN 312 21 Pa rt s 4 a n d 5 Pa rt 5 Pa rt s 6 a n d 7 Pa rt 7

Servic ervice e

Loa oad d dura duration class class

class

Perm -anent

Long term

Medium term

Short term

Instant -aneous

1 ,2

0 .6 0

0 .7 0

0 .8 0

0 .9 0

1 .1 0

3

0 .5

0 .5 5

0 .6 5

0 .7 0

0 .9 0

1 2 3

0 .6 0 0 .6 0 0 .5 0

0 .7 0 0 .7 0 0 .5 5

0 .8 0 0 .8 0 0 .6 5

0 .9 0 0 .9 0 0 .7 0

1 .1 0 1 .1 0 0 .9 0

1 1

0 .3 0 0 .4 0

0 .4 5 0 .5 0

0 .6 5 0 .7 0

0 .8 5 0 .9 0

1 .1 0 1 .1 0

2

0 .3 0

0 .4 0

0 .5 5

0 .7 0

0 .9 0

1 2 1 2

0 .3 0 0 .2 0 0 .4 0 0 .3 0

0 .4 5 0 .3 0 0 .5 0 0 .4 0

0 .6 5 0 .4 5 0 .7 0 0 .5 5

0 .8 5 0 .6 0 0 .9 0 0 .7 0

1 .1 0 0 .8 0 1 .1 0 0 .9 0

Table 2.4 Values Values of k def   (from EC5 EC 5 Table 3.2 3.2)) def  (from Material Standards 1 So lid ti tim m b e r BS EN 1408 140811-1 1 13

Service class 2

3

G lu la m LVL

BS EN 1 4 0 8 0 16 BS EN 1 4 3 7 4 17

0 .6 0

0 .8 0

2 .0 0 a

0 .8 0 0 .8 0 0 .8 0

– 1 .0 0 1 .0 0

–   –   a 2 .5 0

2 .2 5 1 .5 0

– 2 .2 5

– –

2 .2 5 2 .2 5 1 .5 0

– 3 .0 0 –

– – –

 

1 .5 0

2 .2 5

–

 

BS EN 14279 18 P lyw o o d

O SB

Pa rti ticc le  b o a rd

Note a

BS EN 6 3 6 19 Pa rt 1 Pa rt 2 Pa rt 3 BS EN 3 0 0 20 O SB/ 2 O SB/ 3 , O SB/ 4 BS EN 312 21 Pa rt 4 Pa rt 5 Pa rt 6 Pa rt 7

       

Co  C o nsul nsultt m a nufa c tur turee r o n suita suita b ility fo fo r use in se rvi vicc e c la ss 3. 3. P re re se rv a t iv iv e t re re a t m e n t m a y b e n e c e ssa ry.

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2.1 2.17.3 7.3 La La rg e se c ti tio o ns o f so lid ti tim m b e r  If both the thickness and breadth of a solid timber section exceed 100mm it is usually supplied at a moisture content above 20%, as sections of this size are difficult to dry without special arrangements. Therefore, for such sections of solid timber, the Engineer should either specify that it must be specially dried to below 20% moisture content before installation, or use a value of k mod  mod   corresponding to service class 3. In a heated environment large sections may dry out sufficiently to fall within service class 2 conditions so if necessary two separate verifications for strength may  be carried out, out, one with no action assigned assigned a duration duration longer than medium-term medium-term in service class 3, and the other with actions assigned their full term in service class 2. Allowance should be made for movement which will occur during drying out, particularly in respect of green oak 22. Also connection detailing may require special attention.

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3 Des Design ign pr princ inciples iples

3.1 3. 1

Ac tions Act

3.1.1 Typ e s o f a c ti 3.1.1 tio on EC0 distinguishes between permanent actions (dead weight of structure, finishes, permanent fixtures and fixed partitions) and variable actions (every other type of action). 3.1.2 3.1. 2 Ch a ra c te risti ticc va lue s o f a c ti tion on s For permanent actions it is normally acceptable to use an average weight as the characteristic value or, if a range of weights is specified, the highest value in the range. For variable actions an upper characteristic value appropriate to the design life (e.g. once in 50 years) is normally used. However, in ULS load cases where actions can have a favourable effect (e.g. tile weight resisting overturning), the lowest value should be used for permanent loads if a range of weights is specified. Other adjustments for favourable effects are made by means of the partial load factors (see Table 3.1). The values to be used in calculations are: • Characteristic dead load, EC1-1-1 • Characteristic imposed load, EC1-1-1 • Characteristic snow load, BS EN 1991-1-3:  Eurocode 1. Actions on structures. General actions. Snow loads (EC1-1-3)23 • Characteristic wind load, EC1-1-4. 3.1.3 3.1. 3 De sig n va lue s o f a c ti tio o ns For fundamental ULS the characteristic values of actions are converted to design values by the  partial load factors shown in Table 3.1. Additional factors applicable to snow and wind loads are given in the relevant codes. For accidental ULS the load factors for permanent and variable actions are set at 1.0. For SLS the load factor is 1.0, unless the load is favourable (e.g. an imposed load on the second span of a two-span joist) in which case a value of 0.0 should be used.

15

3.1.4 3.1. 4 Ac ti tio o n c o mb ina ti tio o ns Where more than one variable action acts simultaneously, a leading variable action is chosen, and the others are reduced by a specified combination factor. Where it is not obvious which should be the leading variable action, each action should be checked in turn to determine the combination which produces the worst effect. Other factors are used to determine the design value of accidental load combinations and the average value of variable loads in the calculation of creep deformation. All these factors, normally referred to as ‘psi’ factors, are shown in Table 3.2. For examples of their use, see Section 3.2.

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Table 3.1 Partia iall loa load d fac tors for ULSa 

(ba sed on EC 0 NA Tabl ables es NA.A 1. 1.2(A) 2(A) and NA .A1.2(B .A1.2(B)) )) Perma ermanent nent ac tions, cG Unfav avou our rab ablle Fav avou our rab ablle St re re n g t h c h e c ks Eq ui uillib rium c he c ks C o m b in e d e q u il ilib riu m a n d st re re n g t h c h e c ksb

Variable actions, cQ Unfav avou our rab ablle Fav avou our rab ablle

1.35 1.10

1.00 0.90

1.50 1.50

0.00 0.00

1.35

1.15

1.50

0.00

Notes a

b

 Va lue s for for unfa unfa vour vouraa b le e ffe c ts a re for ma in va lue s. Va Va lue s for for fa fa vour vouraa b le e ffe c ts a re fo r a c t io io n s w h ic ic h re re lie v e so m e o f th th e lo a d o n a m e m b e r o r t e n d t o st st a b ilise a me mb e r or str truc uc tur turee . For the d e sig n of ele ele me nts in a fou nd a ti tion on , e .g. ti timb e r p ile s, se e EC 0 A1.3.1(5) A1.3.1(5),, Approach 1.  Th e c o m b in e d c h e c k is a n o p t io io n a l a lt e r n a t iv iv e t o se p a ra t e c a lc u la la t io io n s fo fo r e q ui uillib rium a nd str tree ng th veri verific a ti tion on s whe n b oth ha ve to b e c a rrie d ou t. How e ve r if it is is e m p lo ye d the n it it mu st a lso b e ve rifie d tha t se se tti tting ng cG  to 1. 1.00 00 for for bo th the fa v o u ra ra b le le a n d u n fa fa v o u ra ra b le le p a rt s o f t h e p e rm a n e n t lo lo a d d o e s n o t p ro ro d u c e a le ss fa v o u ra ra b le e ffe c t .

Table 3.2 Fac tors for the rep epr rese esent ntative values values of va var ria iable ble ac ac tions for the buildings cove cover red by this this M  Ma a nua l 

(from EC EC 0 NA Tab le A 1.1) Ac tion

Fac tors for the representative value of an action }0

P e rma n e n t a c ti tio o n s – we ig h ts o f ma te ria ls

 N/ A

 

}1

 

}2

N/ A

1.0 1. 0

a n d p e rm a n e n t fixt u re re s Im p o se d lo a d s in in b ui uilld ing s – c a te g o ry fr fro m EC1-1 C1-1--1  

A: d o m e st ic ic a n d re sid e n t ia ia l a re a s

0.7

0.5

0.3

 

B: o ffic e a re a s

0.7

0.5

0.3

 

C : c o n g re re g a t io io n a re a s

0.7

0.7

0.6

 

D: sh o p p in g a re a s

0.7

0.7

0.6

 

E: stora g e a re a s (i (inc nc lud ing lo fts ts))

1.0

0.9

0.8

 

H: ro o fsa

0.7

0.0

0.0

Sno w lo lo a d s o n b ui uilld ing s – se e EC 11-11-3 3 Sit e s u p t o 1 00 00 0m 0m a b o v e se a le le v e l

0.5

0.2

0.0

Wind Wi nd lo a d s o n b ui uilld ing s – se e EC 11-11-4 4

0.5

0.2

0.0

 

Note a

 Th e ro o f im p o se d lo a d sh o u ld ld n o t b e a p p lie d a t th th e sa m e t im im e a s w in in d o r sn o w  – se e EC 1-1 1-1-1 -1 3.3 .2( 1) 1)..

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EC1-1-1 3.3.1(P) states that when imposed loads act simultaneously with other variable actions (e.g. wind or snow) the total imposed loads on the floors of multi-storey buildings shall be considered as one variable action. For timber structures this requirement is applicable  principally  principal ly to the instantaneous ins tantaneous load case c ase (wind ( wind + snow + floor imposed) imp osed) and a nd to the short-term shor t-term load case (snow + floor imposed). In addition, EC1-1-1 6.3.1.2(11) states than for building “categories A to D, for columns and walls, the total imposed loads from several storeys may be multiplied by a reduction factor an.” an is applicable to buildings with 4 or more storeys, and its values should be taken from the National Annex to EC1-1-1. For timber the medium-term load case (floor imposed) may be critical, and since this does not involve other variable actions the design value of the individual imposed loads from two or more floors may be calculated as Q k , 1 +   / }0, i Q k, i . This value may be reduced by an if and where it is applicable. i>1

3.2

Limi imitt states

This Manual adopts the limit state principle and the partial factor format common to all Eurocodes and defined in EC0. 3.2.1

Ulti tim m a te li lim it sta te s (U (UL LS)

 3.2.1.1  3.2. e finitionsby loss of equilibrium or material failure. All relevant states should be ULS1.1 areD breached checked. • Equilibrium:  –  uplift of the whole or part (e.g. roof) of the structure  –  overturning  –  sliding.  The stability of the foundations should be checked in accordance with EC7. The •

Strength:  –  material rupture in bending, tension, compression or shear   –  stability failure (e.g. buckling of columns, lateral torsional buckling of beams,  – 

stresses induced by–sway portals, diagonalorbracing in roofs walls)failure by connection failure yieldinin the fasteners metal-work, orortimber embedment, shear, splitting, fastener pull-out or head pull-through pull-through..

Where time-dependent deformations (deflections of members or slip in connections) cause a significant redistribution of effects in an assembly or framework, the strength of the members should be considered both before and after creep deformation has occurred. Fundamental design situations occur during the construction phase and in normal use. Accidental design situations occur at or following an exceptional event such as fire, exceptional

17

snowdrift, impact or explosion. All relevant design situations should be considered.

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 3.2.1.2  3.2. 1.2

Loa d c a ses

The load which timber can resist depends on the duration of the load. Therefore a duration should  be assigned to every action action (see Table Table 2.2). When several actions occur simultaneously simultaneously,, a separate load case should be considered for each load duration represented, unless it is obvious that it will not govern the design. The duration of each load case should be taken as the shortest load duration of any load in the load case. For example, a permanent + medium-term + short-term load which can act simultaneously on a member produce three load cases: •  permanent load only (permanent duration load case) •  permanent load + medium-term load (medium-term load case) •  permanent load + medium-term load + short-term load (short-term load case).

 3.2.1.3  3.2. 1.3

D e sig n va lue uess of ac a c tion c om omb b ina inations tions

The design value of the actions combined in any particular load case is calculated as follows. It is usually necessary to try each variable load, Qk , in turn as Qk,1 in order to find the worst case. i) Fundamental design situations (strength or equilibrium)

/c

G, j

Gk, j + cQ, 1 Q k, 1 +  

/c

Q, i

}0, i Q k, i

  ii)

Accidental design situations (fire, impact or explosion) G k, j + (Ad) + }1, 1 Q k, 1 +   }2, i Q k, i  – EC0 expression (6.11b) i>1 i>1   Exceptional snowdrifts (see EC1-1-3, NA.2.4 and NA 2.5)

  iii)

i>1

 – EC0 expression (6.10)

i>1

/

 

/

/ G k, j + Qk , 1 + /  }2, i Q k, i i>1

 – EC0 expression (6.11b)

i>1

     (It is assumed that the snowdrift load is the leading variable action, so Qk,1 represents the (It snowdrift.)

In expression ii),  Ad  is   is in parenthesis because it should be included only when considering the direct effects on a structure of an impact or explosion. It would not be included when considering the situation after such an event or following a fire. For final designs it may be beneficial to use expression 6.10b from EC0 6.4.3.2(3) instead of expression 6.10. iv)

/ pcG, j G k, j + cQ, 1 Qk, 1 +  /cQ, i }0, i Qk, I i>1

 

 

 – EC0 expression (6.10b)

where p = 0.925

This may be used only: • for fundamental (not accidental) design situations • for strength (not equilibrium) verifications • when the leading variable action is wind or snow and it is unfavourable and its characteristic value exceeds 13.5% of the characteristic value of the permanent actions,

or when the leading action is any other type of variable action except storage and its characteristic value exceeds 22.5% of the characteristic value of the permanent actions.

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 3.2.1.4  3.2. 1.4

D e sig n va lue of e ffe ffecc ts of a c tions

In practice it is often convenient to use the above expressions to combine the effects of actions (e.g. bending moments, shear forces) rather than the actions themselves (see EC0 6.3.2). Thus EC0 expression (6.10) becomes:

/ cG, j EG, k, j + cQ, 1 EQ, k, 1 + /cQ, i }0, i E Q, k, i   i>1

  For example, consider a rafter supporting four loads. 1 A full length permanent UDL – e.g. roof weight 2 A partial permanent UDL – e.g. solar panel weight 3 A short-te short-term rm UDL – e.g. snow 4 An instantaneous UDL – e.g. wind  These will produce three load cases with design bending moments calculated as shown in Table 3.3.

Table 3.3 Desi Design gn values of be bending nding mome moment nts – domest domestic fl floo oor r be bea am exa example mple Load Load ads s case

Duration of load lo ad c as ase e

Design value Design value of of bending moment us using EC0 EC0 (6.10) (6.10) (see Sect Sec tion 3.2.1.3(i)) 3.2.1.3(i))

A

1 +2

P e rm a n e n t

 Md

= cG

(Mk, 1 + Mk, 2) =1.35 (Mk, 1 + M k, 2)

B

1+2 +3

Sh o rt

 Md

= cG

(Mk, 1 + Mk, 2) + cQ M k, 3

 

 

=1.35 ( Mk, 1 + Mk, 2) + 1.5M k , 3

C

1 + 2 + 3 + 4 In st st a n ta ta n e o u s  M d  = max maxim imum um of 

cG ( Mk, 1 + Mk, 2) + cQ Mk, 3 + cQ }0, 4 M k, 4

 

and cG ( Mk, 1 + Mk, 2) + cQ Mk, 4 + cQ }0, 3 M k, 3 = max maximu imum m

 

of 

1.35 ( Mk, 1 + Mk, 2) +1.5Mk, 3 + 1.5 # 0.7 # M k, 4

 

and 1.35 ( Mk, 1 + Mk, 2) + 1.5Mk, 4 +1.5 # 0.7 # M k, 3

For each of the three load cases, the resulting bending stress should be compared with the bending strength of the joist calculated for the corresponding load duration. 3.2.2

 3.2.2.1  3.2. 2.1

Se rvi vicc e a b ility lim it sta te s (S (SL LS)

D e finitions

SLS are limit states beyond which specified service criteria are no longer met. In practice these comprise excessive deflection in bending members, joint slip producing excessive deflection, and unacceptable vibration in floors. An irreversible serviceability limit state is a serviceability limit state in which the effects of exceeding it remain when the actions causing it are removed. A

 

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reversible serviceability limit state is one in which the effects of exceeding it disappear when the actions causing it are removed. All relevant SLS should be checked. • Typical irreversible SLS:  –  damage to finishes – e.g. cracking of plasterboard, glass or wall tiles  –   ponding in flat roofs (which may lead to premature failure)  –  damage to masonry produced by excessive deflection of attached structural timberwork   –  deflections of members onto other members not designed to support them. • Typical reversible SLS:  –  malfunction – e.g. windows jamming beneath lintels, gaps beneath partitions  –  unacceptable appearance – e.g. gaps beneath partitions, visually unacceptable deformations in walls, ceilings or exposed beams  –  unacceptable vibration or movement in floors  –  horizontal deflection in upper storeys of medium-rise buildings (provided that this does not cause instability). The term ‘deformation’ covers the deflection of bending members and slip in connections. Slip in connections is the relative lateral movement between the connected members or relative rotation in moment-resisting connections. In frameworks it is usually necessary to consider the effects of slip on the overall deflections of the members. For deformation checks it may be necessary to check either instantaneous deformation or final deformation, or both. Instantaneous deformation is the deformation produced by an action or group of actions at the moment of application, i.e. without any component of creep. Final deformation is the total deformation in a structural member, component or assembly  produced by an action or group of actions at the end of its design life, i.e. instanta instantaneous neous deformation + creep.

 3.2.2.2  3.2. 2.2

Loa d c a ses – SL SLS S

When calculating the design values of actions or the effect of actions for SLS, all partial load factors are set to 1.0, or 0.0 if the loading is favourable. EC0 requires as a principle that “a distinction shall be made between reversible and irreversible serviceability limit states” (EC0 3.4(2)P) and it gives separate expressions for combining actions for the two limit states. However EC5 2.2.3(2) states that the “characteristic combination”, which is normally used only for irreversible limit states, should be used for all calculations of instantaneous deformation. i)  

Instantaneous deformation G k, j + Q k , 1 +   }0, i Q k, i  

/

/

i>1

i>1

– EC0 expression (6.14b)

Creep  C reep deformation is related to the average value of the deforming actions over the design life, which is calculated using the ‘quasi-permanent’ combination. combination.

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ii)  

Creep deformation G k, j +   }2, i Q k, i  

/

/

i>0

i>0

– EC0 expression (6.16b)

The resulting deformation is factored by k def   to produce the creep deformation. def  to

 3.2.2.3  3.2. 2.3

D e sig n va lue of d e form forma a tions

In practice it is generally necessary to use the expressions in Section 3.2.2.2 to combine the deformations produced by the actions rather than the actions themselves (see EC0 6.3.2). i)

Instantaneous deformation =

u inst

  ii)

/ uinst,GjGj + uinst,Q, 1 + /  }0, i uinst, Q, i>1

i>1

Creep deformation u creep

= kdef

/ uinst, Gj + kdef   / }  2, i u inst,Q,i i>0

  iii)

Final deformation ufin = uinst + ucreep

  The  T he expressions in Sections 3.2.2.2 and 3.2.2.3 produce the same final deformations as the method given in EC5 2.2.3(5). As a simpler alternative to ii) and iii) above, ufin may be calculated in the same way as uinst but using final stiffness moduli as given in Section 3.2.3 (see EC5 2.3.2.2(1)). This method gives a conservative solution and is equivalent to omitting the }2 factors in expression ii).

 3.2.2.4  3.2. 2.4

C om omp p on one e nts of de d e fl fle e c tion

Figure 3.1 shows the components of deflection, w, in a simple beam.

w w fin

w

Key Using EC5 symbols: w inst w

w

inst creep

Instantaneous deflection due to permanent and variable loads

creep

Creep deflection due to permanent and variable loads

fin

Total final deflection due to permanent and variable loads

Fig 3.1 

C o m p o n e n ts t s o f d e fle c t io io n in a b e a m w it it h o u t p re c a m b e r (e xtr traa c t fr fro m EC 5 Fi Fig ur uree 7.1 7.1))

22

 

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Precambering a beam will reduce wfin. Large glulam beams can be manufactured with a camber, but precambering is not appropriate for solid timber beams.

 3.2.2.5  3.2. 2.5

Re c om omme me nd e d d e fl fle e c tion limits limits

In Eurocode design none of these is mandatory: the serviceability criteria and limits should be specified for each project and agreed with the client (see EC0 A1.4.2(2)). Tables Tables 3.4 and 3.5 show some suggested limits on deflections.

Table 3.4 3.4 Rec ecommende ommended d vertic ica al de defflec lecttion limits ba bas sed on span, l

(from NA Tab le NA .4 and BS 526 5268-4 8-4.1 .1 C lause 5.1.124 ) Example of use

Limit state

Instantaneous/ Rec ecommende ommended d limits for for Final beams spanning between two supportsa

C ra ra c kin g o f

Irre v e rsib le le

Fin a l

 p la st stee rb o a rd , g la ss,

wfin G

l 250

c e ra m ic s, e tc , in ro o fs,

w h e r e wfin = d e fle c t io io n d u e

c e ilin g s o r fl flo o rs. Also Also

t o p e rm a n e n t + im im p o se se d

re c o m m e n d e d fo fo r

lo a d s + c re re e p .

lin te ls

In c e rta in c irc u m sta n c e s a fini nite te lim it ma y b e m o re a p p ro ro p ria t e , e . g . a ro u n d g la zing

Ap p e a ra n c e o f ro o fs

Re v e rs rsib le le

Fin a l

a nd c e iling s wi with th no a tta c h e d b rittl ttlee fin is ish e s

w fin G

l 150

io n d u e w h e r e wfin = d e fle c t io t o p e rm a n e n t + im im p o se se d lo a d s + c re re e p

In fi fire , a t e nd o f

Ac c id e n ta ta l In st st a n ta ta n e o u s

re q u ire d p e rio d

w inst G

l 20

o f fire re sista nc e ,

w h e r e winst = in sta sta n ta n e o u s

where protection

d e fle c t io io n d u e t o

d e p e n d s o n a tta c h e d

 p e rm a n e n t + im p o se d lo a d s

 p la st stee rb o a rd , u n le ss  p ro ve d b y t e st

Note a

For ca nti ntille ve rs, the the limi mitt b a se d on the c a nti ntille ve r sp a n o f l s  sh h o u ld ld b e d o u b le d .

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Table 3.5 3.5 Rec ecommende ommended d hor horizont izontal de defl flec ecttion limits Exam amp ple of of use

Limit state

Instan anttan aneo eou us/ Rec ecommende ommended d limit limits s

23

Final Porta l fra m e s wi with th

Irre v e rsib le le

In st st a n t a n e o u s

m a so n ry o r la rg e

winst inst, Q G

he 300  

a re a s o f g la ss

w h e r e winst,Q  = in sta sta n ta n e o u s

with wi th in in th e p la n e o f

h o rizo n ta l d e fle c ti tio o n a t to p o f

t h e fr f ra m e

c o lu lu m n o r st o re re y c a u se se d b y wind. re y he = h e ig h t o f c o lu m n o r sto re

Porta Por ta l fra m e s

Re v e rs rsib le le

In st st a n ta ta n e o u s

with wi th o u t m a so n ry

winst inst, Q G

he 200

o r la rg e a re a s o f

w h e r e winst,Q  = in sta sta n ta n e o u s

g la ss withi within n th e

h o rizo n ta l d e fle c ti tio o n a t to p o f

 p la n e o f t h e fra m e

c o lu lu m n o r st o re re y c a u se se d b y wind.

he = h e ig h t o f c o lu m n o r sto re re y Tim b e r fra m e

Irre v e rs rsib le le

In st st a n ta ta n e o u s

d we lling s wi with th

Th e d e sig n m e t h o d a uto m a ti ticc a lly li lim its the

Re v e rs rsib le le

m a so n ry ry

In st st a n ta ta n e o u s

in st st a n t a n e o u s d e fle c t io io n t o Tig h te r lim its, e .g . he/500, he/ 333. Ti m a y b e a p p ro xi xim a t e ly o b t a in e d  b y in c re a si sin n g t h e ra c ki kin ng str tree n g th p ro p o rti tio o n a te ly . he = store store y he ig ht

Ma son ry wa lls

Irre v e rsib le le

In st st a n t a n e o u s

winst  G 6 m m w h e r e winst = in in st st a n t a n e o u s h o ri rizo n t a l d e fle c t io io n a t e a c h e a v e s c a u se se d b y sp sp la y in g o f c o ll lla r tr tru u ss ss u n d e r d e a d + im p o se s e d lo a d

Irre v e rs rsib le le

Fin a l

winst + wcreep  G  he/6 5 0 w h e r e winst i  iss d e fin e d a s a b o v e a n d wcreep i  iss c re e p d e fo r m a t io io n u n d e r a ll lo a d s he = h e ig h t o f b u il ild in g to e a v e s

in d we lling s  – h o ri rizo zo n t a l d e fle c t io n a t e a c h e n d o f a ra ise d t ie ie truss Ma son ry wa lls in d we lling s  – h o ri rizo zo n t a l d e fle c t io n a t e a c h e n d o f a ra ise d t ie ie truss

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3.2. 2.3 3 Cr Cree e p e ffe c ts in a sse m b lie s 3. In an assembly consisting of timber components with different creep properties or a mixture of members made of timber and other materials, the distribution of moments and forces will change over time. This also occurs in assemblies with mechanically fastened connections, because EC5 states that the value of k def    should be doubled for mechanically fastened connections (see def  should Section 6.13.4), giving them different time-dependent properties from the main timber members.

The final stresses and deformations may be calculated using the appropriate design loads from Section 3.2.1.3 i) to iv) for ULS or Section 3.2.2.2 i) for SLS, in conjunction with reduced values of the stiffness moduli of each member and connection. These are calculated as follows:  E mean

=

1 + k def

]

mean an, fin fin  E me

 

g

mean an, fin fin G me

G mean

=

1 + k def

]

 

g 

K ser 

= ser, fi fin n K ser

 ^

1 + k def, jo int

h

using the appropriate values for each member or connection. For the values of K ser    and ser  and k def,joint respectively. def,joint see Sections 6.13.2 and 6.13.4 respectively. It is recommended that these expressions be used for both ultimate and serviceability limit states. 3.2.4 3.2. 4 Use o f fra m e a na lys ysiis p ro g ra m s For solid timber, glulam and LVL use  E 0,mean 0,mean  and Gmean. If values for stiffness moduli  perpendicular to the grain are required, use E0,mean/30 for softwoods and softwood glulam,  E 0,mean 0,mean/15 for hardwoods and Gmean/16 for both. For plywood and OSB use  E ct,0 ct,0 or  E ct,90 ct,90 as appropriate, and Gmean, the shear modulus for  panel shear. For plywood use the value of E ct ct appropriate to the direction of load to the grain direction of the surface veneer veneer.. For LVL see Table 3.16 or the manufacturer’s literature. (See Tables 3.14 to 3.18 for values.) For initial designs ignore slip in connections. For final, more accurate designs, if the  program allows a spring stiffness to be entered at connections, use the appropriate value of the slip modulus (see Section 3.2.3). Otherwise insert a short fictitious element between each member and its adjacent connections, continuous with the member and with a stiffness equivalent to the connection – e.g. a 1mm long element with a 1mm 2 cross-section and a modulus of elasticity of  E   = nK ser    N/mm2  or  E fin ser  N/mm fin  = nK ser,fin ser,fin N/mm2, as appropriate, where n is the number of fasteners. (With bolted joints an additional 1mm lack of fit should be entered.) To analyse an assembly after creep occurs use the approximate method given in 25

Section Some 3.2.3 or referanalysis to TRADA’s European Guidance GD5 frame programs require values Document of Poisson’s ratio,. o, which are used to calculate shear moduli via the formula G = 0.5 E /(1 /(1 + o). This formula is not applicable to timber and wood based composites, so where Poisson’ Poisson’ss ratio is required an equivalent value o should be inserted, where o  = ( E  –  – 2 G)/2G. l

l

3.2.5 Flo o r vi vib b ra ti tio on Limiting floor vibration is a serviceability limit state which is covered in Section 8.4.3.2.

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3.3

Timbe imber r ma matteria ials ls

3.3.1 Str 3.3.1 truc uc tur turaa l ti tim m b e r m a te ria ls A summary of the most common types of structural timber materials is shown in Table 3.6. Definitions are provided in the Glossary.

Benefi Bene fits ts of using using ti timbe mbe r  •

Timber has a relatively high strength:weight ratio compared with other materials,  producing light-weight structures which require lighter foundations and make them  particularly suitable for brownfield developments.

25

•

Timber materials are relatively resistant to both acids and alkalis, and are therefore a good Timber choice for corrosive environments such as salt barns and swimming pools.

•

Most structural timber originates from sustainable plantations (and may be specified as such) so in general it may be regarded as a renewable material. Timber’s low thermal conductivity and low thermal mass help to ensure good heat retention and reduce the heat required to warm a building up. Producing structural timber materials requires relatively little energy compared with other structural materials, resulting in less damage to the environment. Sources of information on the procurement of timber from sustainable sources are listed on the website of CPET, the Central Point of Expertise on Timber Procurement.

• • •

3.3.2 3.3. 2 Dim e ns nsiion s a nd tol tolee ra nc e s For further information see BS EN 336 26, BS EN 1313-227 and BS EN 39028.

 3.3.2.1  3.3. 2.1

Le ng th

 3.3.2.2  3.3. 2.2

Thic kne ss a nd w id idth th

Solid timber for construction is normally available in lengths from 1.8m to 5.4m or up to 7.2m on order, in steps of 0.3m. European oak can be obtained in lengths up to 8m, or a little more  by special arrangement, and tropical hardwoods up to 9m to 12m, depending on the species. The maximum length of LVL that is produced is 23m and the maximum length of glulam is limited only by transport considerations, however maximum stock lengths of LVL and glulam are generally 12m and 15m respectively.

Timber is initially sawn to size: the resulting dimensions are commonly called ‘sawn sizes’. It may then be machined or planed to a more exact size as follows: • timber machined on the two narrower faces is particularly suitable for joists for which an accurate depth is required, this is commonly called ‘regularised timber’ but should be called ‘machined on the width’ timber machined on all four faces is commonly referred to as ‘PAR’ or planed all round. It is used in trussed rafters and wall panels and for exposed timbers where appearance is important ‘CLS/ALS’ timber (Canadian Lumber Sizes or American Lumber Sizes) is machined all round and is imported from North America and some Scandinavian countries. It has rounded arrises and is usually lightly waxed.

•

•

26

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Standard cross-sectional dimensions are shown in Section 3.3.2.4.

Table 3.6 3.6 Struc ucttur ura al timbe imber r ma matteria erials ls Material

Uses

C omments

So lid softwood

Jo ists sts,, lilig ht b e a m s, wa ll fra m ing , lilig ht c o lum ns, roo fing , b ra c ing m e m b e rs, c o n c re t e fo r m w o rk rk. Ma Ma y  b e u se d e xte rn rnaa lly w ith  p re se rva tive tre a tm e n t

Re la t iv iv e ly ly c h e a p a n d re a d ily a v a ila b le fro m m a n a g e d p la n t a t io io n s. s. Le ss str stron on g tha n othe r ti tim m b e r a lte rna ti tive ve s

So lid h a rd w o o d

Be a m s a n d c o lu lu m n s, e xp x p o se se d b e a m s a n d

Str tron on g e r a nd sti tifffe r tha n soft softwo wo od , a nd m a n y sp sp e c ie s a re a v a ila b le in la la rg e r

c ol olum um ns ns,, p ort ortaa l fra m e s, tim ti m b e r b rid g e s, la rg e roo f m e m b e rs, ha h a rb o u rs rs a n d groynes

se c t io io n s. So m e sp e c ie s a re m o re d u ra ra b le t h a n so so ft ft w o o d s a n d a re m o re re sist a n t to fi fire . Ca re ne e d e d if if re q ui uirre d from a sus usta ta ina b le sou rc e

G lu la m , LVL VL,, PSL, LSL

Be a m s, c o lum ns, ro o fing , a rc h e s, d o m e s a n d p o rt rt a l fra m e s, tim tim b e r b rid g e s. Ma y be us usee d e xte rna lly with with  p re se rva tive tre a tm e n t a n d g o o d d e t a ilin g

La rg e me mb e rs, m or oree sta b le d ime ns nsiion a lly tha n so lid ti tim m b e r. ST STC s a re sti stifffe r a nd str tron on g e r tha n sol soliid softwoo softwoo d of the sa me sp e c ie s. Be st prote prote c te d from from the we a the r if usee d e xte rna lly us

P ly w oo oo d

Flo o r a n d ro ro o f d e c kin g , w a ll ll sh e a t h in in g , b o x b e a m a n d I-j -jo o ist we b s, truss truss g usse ts

Ext e ri rio r g ra ra d e s m a y b e p re fe ra b le t o O SB fo r m o re hum id e nvi nvirro nm e nts or situa ti tion on s whe re we tti tting ng ma y oc c ur or und e r lo ng te rm lo lo a d ing , e .g. in in fl fla t ro ro o fs. Birc h p lywoo d is str stro o ng e r tha n O SB a nd  p a rtic le b o a rd

O SB

Flo o r a nd n d ro o f d e c ki kin g , w a ll ll sh e a t h in in g , b o x b e a m a n d I-j -jo o ist we b s

The p re fe rre d c ho ic e on c ost g rou nd s for t im im b e r fra m e w a ll p a n e ls a n d t h e w e b s o f I-j I-jo o ists sts.. Also Also u se d fo r flo o r d e c ki king ng ,  p a rtic u la rl rly y th e stru c tu ra l d e c ki kin n g in p a rty floo rs. Hi Hig h c re e p fa c tor unde r lon g te rm loa d ing

Pa rti ticc le  b o a rd (a lso kn o w n a s c h ip ip b o a rd )

Flo o r d e c kin g

It s m a ss ss a nd n d p ric e m a ke ke itit v e ry ry su it a b le fo fo r flo or de c king in a d ry e nvi nvirro nm e nt. Must Must n o t b e e xp o se s e d t o t h e w e a t h e r o n b u il ild in in g site s, a nd is m o re b rittl ttlee tha n p lywoo d . Hig h c re e p fa c t o r u n d e r lo n g t e rm lo a d in g

Ha rd b o a rd

St ru c t ur u ra l sh e a t h in in g a n d b o x  b e a m a n d I-j -jo o ist w e b s in d ry e nvi nvirron me nts

Te m p e re d h a rd b o a rd is is st ro ro n g e r a n d m o re re re sista nt to to wa te r a b sorpti orption on tha n othe r type s of fi fib re b ui uilld ing b o a rd . Its Its prop prop e rti tiee s  Ma a nua l a re no t c ove re d in in this this M

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Table 3.7 Dimensiona Dimensionall tole oler ranc nces es for solid timbe imber r, glula glulam m and LVL Solid timbe timber r (BS (BS EN 33626) To le ra n c e c la ss T1 – sa w n d im e n sio n s T2 – m a c h in e d d im e n sio n s Le ng th

Fo r d im e nsi nsio o ns

G 100  100m mm

Fo r d im e nsi nsio o ns > 100mm

+ 3 / -1 m m

+ 4 / -2 m m

±1 m m

±1 .5 m m

Fo r sup p ly: no t le le ss tha n the le ng th spe c ifie d Fo r c o nst nstrruc ti tio o n: a t the d e sig ne r’s d isc re ti tio on

Glula lulam m (BS EN 39028) Th ic kne ss ss,, b  Depth, h

Sq ua re ne ss o f c ro ss-se c ti tio on

±2mm Fo r h  G 400  400m mm

Fo r h > 400m 400m m

+ 4 / -2 m m + 1 / -0 .5 m m p e r 1 0 0 m m Ma xim u m d e v ia ia ti tio o n ffrro m a rig h t a n g le : 2mm p e r 100 100m m m , or ± 1. 1.15° 15°

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Le ng th, l

Fo r l  G 2  2m m

Fo r 2 m < l  G 2 0m

Fo r l > 20m

± 2m m

± 1 m m p e r m e t re

± 20m m

LVL (BS EN 14374 1437417) Th ic kne ss ss,, b

+(0.8+0.03b)/-(0.4+0.03 b) m m

Wid Wi d th, h

Sq ua re ne ss o f c ro ss-se c ti tio on

Fo r h < 400m 400m m

Fo r h  H 400  400m mm

± 2m m

± 0 .5 %

Ma xim u m d e v ia ia ti tio o n fr fro m a rig h t a n g le : 2mm p e r 100 100m m m , or ± 1. 1.15° 15° ± 5m m

Le ng th, l

 3.3.2.3  3.3. 2.3

Ta rg e t siz size e s and tol tole e ran rancc e s

Thickness and width are specified as target sizes which refer to the dimensions at 20% moisture content for solid timber and at 12% moisture content for glulam and structural timber composites. Engineering calculations should be based on target sizes, even though at other moisture contents the thickness and width will change a little (see Section 2.8.1). This is because reductions in crosssection are compensated for by increases in strength and stiffness, and vice versa. The permitted tolerances on target sizes at the reference moisture content are shown in Table 3.7.

 3.3.2.4  3.3. 2.4

Stand a rd size size s

Tables 3.8 to 3.10 show the most commonly available target sizes for softwood and hardwood sections used in UK construction. Tables Tables 3.11 to 3.13 show the most commonly available glulam and LVL section sizes.

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Tabl ble e 3.8 Preferred softwood softwood sizes sizes (BS EN 33626) Thic kness (mm)

Finish

Fin ish

Sa w n

75

1 00

120

15 0

1 75

20 0

2 25

250

27 5

300

Ma c h in e d

72

97

120

14 5

1 70

19 5

2 20

245

27 0

295

Sa w n

Ma c h in e d

22

19

25

22

38

35

47

44

63

60

75

72

1 00

97

1 50

145

Ke y :

Width (mm)

= m o st c o m m o n ly ly a v a ila b le = g e n e ra lly a v a ila b le = n o t g e n e ra lly a v a ila b le

Table 3.9

C LS/ ALS (p (pla laned ned all all round) soft softwoo wood d sizes (BS EN 33 336 626)a Wid idth th (m (mm) m)

Thic hickne kness ss (mm)

63

89

1 14

140

18 4

23 5

2 85

38

Ke y :

= m o st c o m m o n ly ly a v a ila b le = g e n e ra lly a v a ila b le

Note a

The se size s a re c o m m o nl nly y use use d fo r wa ll stud s in in p la tf tfo o rm ti tim m b e r fra m e b ui uilld ing s.

Table 3.10 Preferred ha hardwoo rdwood d size izes s (BS EN 131 13133-2 227) Thic kness (mm)

Finish

Fin ish

Sa w n

50

60

70

80

90

1 00

12 0

Ma c h in e d

47

57

67

77

87

97

11 5

Sa w n

Ma c h in e d

19

16

26

24

38

35

52

49

63

60

75

72

Ke y:

Width (mm) C o n t in u e in 2 0 m m st e p s u p t o 3 00 00 m m d e p e n d in in g o n sp e c ie s

= p re fe rre d si sizze s fr fro o m BS EN 1313-2 (c o n sul sultt sup p lie r for a va ila b ility)

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Table 3.11 Typic ypica al glulam sec secttions – based based on Imperial sizes (more c ommon) Depth (mm) Breadth (mm)

22 5

27 0

31 5

36 0

40 5

4 50

4 95

5 40

5 85

6 30

6 75

65 90 11 5 14 0 16 5 19 0 Ke y:

= typ ic a l size s a va ila b le o ff the she lf = typ ic a l si sizze s

Note a Sq u a re

a n d ro u n d se c t io io n s a re a lso a v a ila b le fo r c o lu m n s.

Table 3.12 3.12 Typic ypica al glulam sec ecttions – Metric sizes sizes Breadth (mm) 60

Depth (mm) 2 40

28 0

32 0

36 0

400

480

5 20

80 10 0 12 0 14 0 16 0 18 0 20 0 Ke y:

= typ ic a l size s a va ila b le o ff the she lf = typ ic a l si sizze s

Note a

Sq u a re a n d ro u n d se c t io io n s a re a lso a v a ila b le fo r c o lu m n s.

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Table 3.13 Typ ypic ica al LVL sec secttions Depth (mm)

Breadth (mm) 20 0

26 0

30 0

36 0

40 0

45 0

50 0

60 0

90 0

18 0 0

27 33 39 45 51 57 63 75 Ke y:

= typ ic a l si sizze s

Glulam can be manufactured in very large sections and lengths, but lengths above 15m may be difficult to transport. One large manufacturer quotes data for sizes from 90mm wide#180mm deep to 240mm wide#2050mm deep, and up to 31m in length. The Glued Laminated Timber Association (GLTA) quotes data for sizes from 65mm #180mm to 215mm#1035mm. Some manufacturers also stock glulam machined to a round cross-section. Glulam is usually manufactured from laminations 33mm or 45mm thick: 33mm for curved members and 45mm for straight or nearly straight members. Some straight glulam made from pressure-treated material may also use 33mm laminates. The depth is therefore generally a multiple of 33mm or 45mm. For more information consult a supplier or the GLTA.

Before completing a design it is advisable to check with a stockist that the proposed sizes are available. Prefabricated timber joists are made in standard sizes which should be selected from the catalogue of the chosen manufacturer. There are also specialist manufacturers of timber engineering hardware whose catalogues should be consulted for both sizes and prices. A comprehensive on-line list of stockists of timber and timber-related products can be accessed at www www.trada.co.uk. .trada.co.uk.

 3.3.2.5  3.3. 2.5

Stre Str e ng th g rad ing a nd str stre e ng th c la ss sse es

All timber for load-bearing use in construction must be strength graded by an approved grading body, either visually according to standardised rules or by means of a grading machine supplemented by visual rules. (For further information see references 13, 22, 29, 30 and 31.) The visual grades used in the UK are GS (General structural) and SS (Special structural) for softwoods and HS (Hardwood structural) for tropical hardwoods. There are special grades for the home grown temperate hardwoods oak and sweet chestnut, and for unseasoned oak. To simplify design, combinations of species and grade are grouped into sets of strength classes, each of which has a corresponding set of characteristic material properties which are safe for all the species/grade combinations in the class. The strength classes for softwoods, poplar and

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tropical hardwoods are designated by a letter and a number. The letter ‘C’ (coniferous) generally indicates softwoods or poplar and ‘D’ (deciduous) generally indicates hardwoods, while the number refers to the characteristic bending strength of the class in N/mm2. Glulam is manufactured from graded timber in one of two forms: homogenous, in which every laminate is of the same grade, or combined, in which higher grades are used in the outer laminates. The resulting lay-ups are assigned to special glulam strength classes, each with its own set of characteristic material properties. Every length of graded solid timber or glulam must be stamped with the grade, species or strength class, and the registered number of the grading agency. Solid timber and glulam are normally specified by strength class. Where there are  particular requirements, e.g. appearance or local source, a species and strength grade may be specified instead. For solid hardwoods, it is usually necessary to specify ‘HS grade’ and a  particular species. 3.3. 3. 3.3 3

Ch a ra c te risti ticc va lue s

Tables 3.14 to 3.18 give characteristic values for some common timber materials. For more comprehensive tables see the CD. The bending strength and stiffness classes for plywood given in BS EN 12369-232 appear to be of little practical use. Either seek characteristic values directly from the manufacturers, or convert the grade values tabulated in BS 5268-2 3  for particular types of plywood to safe characteristic values as follows:  X k  k    E k  k  

= 2.7 X grade grade = 1.8 E grade grade

Where  X k  = a characteristic strength property k    X grade 40-56 grade  = the corresponding grade strength property from BS 5268-2 Tables 40-56  E k  

= a characteristic stiffness property

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