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AS 3850.2:2015
A S 3 8 5 0 .2 : 2 0 1 5
) d e t n i r p n e h w d e e t n a r a u g t o n y c n e r r u c t n e m u c o D ( 6 1 0 2 b e F 4 2 n o D T L Y T P A I L A R T S U A E K R U O R O G N I A L y b d e s s e c c A
Prefabricated concrete elements Part 2: Building construction
This Australian Standard® was was prepared by Committee BD-066, Tilt-up construction. It wa was s approved on behalf of the Council of Standards Australia on 8 July 2015. This Standard was published on 3 September 2015.
The following are represented represented on Committee BD-066:
• • • • • • • • • • • • • •
) d e t n i r p n e h w d e e t n a r a u g t o n y c n e r r u c t n e m u c o D ( 6 1 0 2 b e F 4 2 n o D T L Y T P A I L A R T S U A E K R U O R O G N I A L y b d e s s e c c A
• • • • •
Australasian Fire and Emergency Emergency Service Authorities Council Council Australian Council of Trade Trade Unions Australian Engineered Engineered Fasteners and Anchors Counc Councilil Australian Institute of Building Building Surveyors Australian Steel Institute Building Designers Association of NSW Cement Concrete and Aggregates Australia Concrete Institute of Australia Concrete Pipe Association of Australasia Crane Industry Council of Australia Curtin University of Technology Engineers Australia Master Builders Australia National Association of Testing Authorities Australia National Precast Concrete Association Australia Steel Reinforcement Institute of Australia Sydney University WorkCover New South Wales WorkSafe Victoria
This Standard was issued in draft draft form for comment as DR2 AS 3850.2. Standards Australia wishes to acknowledge the participation of the expert individuals that contributed to the development of this Standard through their representation on the Committee and through the public comment period.
Keeping Standards up-to-date Australian Standards® are living documents documents that reflect progress in science, science, technology and systems. To maintain their currency, all Standards are periodically reviewed, and new editions are published. Between editions, amendments may be issued. Standards may also be withdrawn. It is important that readers assure themselves they are using a current Standard, which should include any amendments that may have been published since the Standard was published. Detailed information about Australian Standards, drafts, amendments and new projects can be found by visiting www.standards.org.au www.standards.org.au Standards Australia welcomes suggestions for improvements, and encourages readers to notify us immediately of any apparent inaccuracies or ambiguities. Contact us via email at
[email protected],, or write to Standards Australia, GPO Box 476, Sydney, NSW 2001.
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AS 3850.2:2015
®
Australian Standard Standard
Prefabricated concrete elements ) d e t n i r p n e h w d e e t n a r a u g t o n y c n e r r u c t n e m u c o D ( 6 1 0 2 b e F 4 2 n o D T L Y T P A I L A R T S U A E K R U O R O G N I A L y b d e s s e c c A
Part 2: Building construction
First published as AS 3850.1—1990, AS 3850.2—1990 and AS 3850.3—1992. AS 3850.1—1990, AS 3850.2—1990 and AS 3850.3—1992 3850.3—1992 revised, amalgamated and redesignated as AS 3850—2003. AS 3850—2003 revised and redesignated (in (in part) as AS 3850.2:2015.
COPYRIGHT
© Standards Australia Limited All rig hts are res erv ed. No par t o f t his wor k m ay be rep rod uce d o r c opi ed in any for m o r b y any means, electronic or mechanical, including photocopying, without the written permission of the publisher, unless otherwise permitted under the Copyright Act 1968. Published by SAI Global Limited under licence from Standards Australia Limited, GPO Box 476, Sydney, NSW 2001, Australia ISBN 978 1 76035 243 1
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PREFACE This Standard was prepared by the Stand ards Australia Committee BD-066, Tilt-up Construction, to supersede AS 3850—2003, Tilt-up concrete construction. This Standard is part of a series, which comprises the following parts: AS 3850 3850.1 3850.2
Prefabricated concrete elements Part 1: General requirements Part 2: Building construction (this Standard)
The objective of this part of the Standard is to provide requirements for planning, construction, design, casting, transportation, erection and incorporation into the final structure of prefabricated concrete elements in building construction. In this Standard where the word ‘shall’ is used, a mandatory requirement is implied; where the word ‘should’ is used, a recommendation is implied. Statements expressed in mandatory terms in notes to tables are deemed to be requirements of this Standard. ) d e t n i r p n e h w d e e t n a r a u g t o n y c n e r r u c t n e m u c o D ( 6 1 0 2 b e F 4 2 n o D T L Y T P A I L A R T S U A E K R U O R O G N I A L y b d e s s e c c A
The term ‘normative’ has been used in this Standard to define the application of the appendix to which it applies. A ‘normative’ appendix is an integral part of a Standard.
This document includes commentary on some of the clauses, tables and figures of the Standard. The commentary directly follows the relevant clause, table or figure, is designated by ‘C’ preceding the clause number and is printed in italics in a box. The commentary is for information and guidance and does not form part of the Standard.
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CONTENTS
Page SECTION 1 SCOPE AND GENERAL 1.1 SCOPE...................................................... .................................................................................. ......................................................... ....................................... .......... 5 1.2
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NORMATIVE REFERENCES ....................................................... .................................................................................... ............................. 5
SECTION 2 DESIGN AND DOCUMENTATION 2.1 GENERAL..................................................... ................................................................................. ......................................................... .................................. ..... 6 2.2 DESIGN STAGES ......................................................... ..................................................................................... .............................................. .................. 6 2.3 ERECTION DESIGN ......................................................... ..................................................................................... ......................................... ............. 6 2.4 BUILDING STABILITY DURING ERECTION AND CONSTRUCTION ................ 7 2.5 DESIGN FOR MANUFACTURE, HANDLING AND ERECTION ERECTION............................ 8 2.6 JOINT WIDTHS ...................................................... .................................................................................. .................................................. ...................... 33 2.7 FOOTINGS.......................................... FOOTINGS....................................................................... ......................................................... ......................................... ............. 34 2.8 CONNECTIONS ....................... ................................................... ....................................................... .................................................... ......................... 35 2.9 STRONGBACKS ................................................... .............................................................................. ................................................... ........................ 37 2.10 DOCUMENTATION....................................................... .................................................................................. .......................................... ............... 38 2.11 TOLERANCES.................................... TOLERANCES............................................................... ...................................................... ........................................... ................ 39 SECTION 3 CASTING 3.1 GENERAL....................................................... .................................................................................. ...................................................... ............................... .... 44 3.2 LAYOUT ................................................... ............................................................................... ....................................................... .................................... ......... 44 3.3 CASTING BED ..................................................... ................................................................................ .................................................... ......................... 44 3.4 SURFACE FINISH AND FORMWORK FORMWORK..................................................... ................................................................... .............. 44 3.5 CURING AND RELEASE AGENTS .................................................... ........................................................................ .................... 44 3.6 LIFTING, BRACE AND FIXING INSERTS ................................................... ............................................................ ......... 45 3.7 WELDING...................................................... .................................................................................. ....................................................... ............................... .... 45 3.8 IDENTIFICATION AND ORIENTATION ..................................................... ............................................................... .......... 45 3.9 INSPECTION ................................................... .............................................................................. ....................................................... .............................. .. 45 3.10 COMPACTION OF CONCRETE.......................... ..................................................... .................................................... ......................... 46 3.11 ELEMENT RELEASE (LIFT-OFF (LIFT-OFF FROM CASTING BED) .................................... .................................... 46 SECTION 4 TRANSPORT, CRANAGE AND ERECTION 4.1 4.2 4.3 4.4 4.5
TRANSPORT ................................................... ............................................................................... ....................................................... ............................. .. 47 STORAGE AND MULTIPLE HANDLING .................................................... .............................................................. .......... 49 CRANES AND RIGGING.................................................... ................................................................................ ..................................... ......... 49 ERECTION........................................ ERECTION.................................................................... ....................................................... ............................................ ................. 51 DAMAGE AND REPAIR..................................................... ................................................................................. ..................................... ......... 56
SECTION 5 TEMPORARY SUPPORTS 5.1 INSTALLATION AND INSPECTION OF TEMPORARY BRACING AND PROPPING ....................................................... .................................................................................. ....................................................... .............................. .. 57 5.2 SUPERIMPOSED SUPERIMPOSED LOADS ..................................................... ................................................................................ ................................... ........ 57 5.3 LEVELLING PADS AND SHIMS ................................................... ............................................................................ ......................... 57 5.4 GROUTING OF THE BASE ...................................................... ................................................................................. ............................... .... 58 SECTION 6 INCORPORATION INTO FINAL STRUCTURE 6.1 FIXING TO FINAL STRUCTURE ....................................................... ........................................................................... .................... 59 6.2 INSPECTION AND REMOVAL REMOVAL OF TEMPORARY SUPPORTS............................ ............................ 59
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Page APPENDIX A INFORMATION REQUIRED REQUIRED ON DRAWINGS ............................. ........................................... .............. 60 BIBLIOGRAPHY...................................................................... ................................................................................................... ............................................... .................. 63
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STANDARDS AUSTRALIA Australian Standard Prefabricated concrete elements
Part 2: Building construction
S E C T I O N
1
S C O P E
A N D
G E N E R A L
1.1 SCOPE
This Standard provides requirements for planning, construction, design, casting, transportation, erection and incorporation into the final structure of prefabricated concrete elements in building construction. It applies to prefabricated concrete elements including, but not limited to, wall elements, columns, beams, flooring and facade elements used in building construction. This Standard does not cover the following elements: ) d e t n i r p n e h w d e e t n a r a u g t o n y c n e r r u c t n e m u c o D ( 6 1 0 2 b e F 4 2 n o D T L Y T P A I L A R T S U A E K R U O R O G N I A L y
(a)
Concrete pipes, bridge beams or culverts (e.g. concrete pipes or culverts used in civil
(b)
construction works to channel water under roads, railways or embankments). Small individual concrete elements that can be handled manually (e.g. bricks, blocks and pavers).
NOTE: The element ele mentss ment m entione ioned d in Ite Items ms ( a) and (b) are cove covered red by othe otherr Austra Au stralia lian n St Standa andards. rds.
1.2 NORMATIVE REFERENCES
The following are the normative documents referenced in this Standard: NOTE: Document Docu mentss rrefer efer enced ence d fo r inform in formati ative ve purpo purposes ses are lis ted in the Bibl Bibliogr iography aphy..
AS 2550
Cranes, hoists and winches—Safe use (series)
3610 3610.1
Formwork for concrete Part 1: Documentation and surface finish
3850 3850.1
Prefabricated concrete elements Part 1: General requirements
4100
Steel structures
AS/NZS 1100 1100.501
Technical drawing Part 501: Structural engineering drawing
1170 1170.0 1170.2:2011
Structural design actions Part 0: General principles Part 2: Wind actions
1554 1554.3
Structural steel welding Part 3: Welding of reinforcing steel
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S E C T I O N
2
D E S I G N
A N D
D O C U M E N T A T I O N
2.1 GENERAL
This Section specifies requirements for the construction design and documentation of prefab pre fabric ricate ated d conc c oncret retee eelem lem ents. ent s. NOTE: Designe Des igners rs should shou ld refe referr to the Nati National onal Construc Cons truction tion Code (NCC (NCC)) Volu Volume me 1, Sect Section ion C: Fire resistance, for fire design requirements.
2.2 DESIGN STAGES
The following two separate design stages shall be considered: (a)
In-ser Inservic vicee ddesi esign gn NOTES : 1 The in-service design provides for the performance of the element as part of the permanent structure. For in-service design, see AS 3600 or AS 4100 for examples. 2 The in-service designer should consider the practicality of the construction process.
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(b)
Erecti Ere ction on des design ign The element shall be designed to resist all handling forces, including impact, arising out of stripping, storage, transport, lifting, and temporary bracing and propping. a temporary structure. While in the braced condition, the element shall be regarded as NOTES : 1 The erection designer should pay particular consideration to the stability of the structure during all phases of the construction process, including loads applied due to staged construction. 2 Consideration should be given to the NCC regarding fire performance during construction.
C2.2
The NCC Volume 1 includes requirements for the design for fire requirements.
The design of prefabricated concrete buildings for fire is a complex matter and the design should take into consideration the behaviour of the building under fire conditions. Reference should be made to the NCC and its commentary, with particular attention to the structural adequacy provisions in the event of fire. 2.3 ERECTION DESIGN
The design shall take into account the interrelation of the various stages of manufacture, construction, transport and erection.
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C2.3
The full benefit and economies inherent in prefabricated methods of construction are only possible with preplanning and coordination between all parties. Close collaboration between the in-service designer, erection designer, principal contractor and subcontractors, manufacturer, and the erector is necessary to ensure safety in construction. Pri or to man Prior manufa ufactu cturin ringg the t he prefab pre fabric ricate atedd con concre crete te elemen ele ments, ts, the princi pri ncipal pal contra con tracto ctor, r, in association with the erection designer, the manufacturer and the erector, should have pla nnedd the planne t he comple com plete te con constr struct uction ion and ere erecti ction on seq sequen uences ces.. Consideration should be given to details such as the following:
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(a)
Site limitations.
(b)
Local street access.
(c)
Element sizes, shapes and masses.
(d)
Crane size, mobility and access.
(e)
Casting sequence.
(f)
Overhead obstructions (e.g. to cranage and temporary work platforms), especially overhead power lines.
(g)
Lifting, handling and erection sequence.
(h)
Construction sequence.
Des igners Design ers sho should uld giv givee due con consid sidera eratio tionn to han handli dling ng req requir uireme ements nts and transp tra nsport ort limitations during the planning and design of the elements. Consultation with the transport contractor, if available, is recommended during the design phase, so as to avoid potential changes due to transport limitations. Alt hough Althou gh specia spe ciall veh vehicl icles es mig might ht be ava availa ilable ble,, por portio tionn elemen ele ments ts sho should uld be pro propor portio tioned ned so that they can be transported on standard vehicles during normal working hours. 2.4 BUILDING STABILITY DURING ERECTION AND CONSTRUCTION
The stability design of the whole building shall be checked for each stage during erection, up to completion. Special care shall be taken in design and construction to guard against progre pro gressi ssive ve collap col lapse se during dur ing constr con struct uction ion.. C2.4
During construction, prefabricated concrete structures are susceptible to progre pro gressi ssive ve col collap lapse. se. The failur fai luree of a sin single gle bra bracin cingg or pro proppi pping ng mem member ber sho should uld not lead to the disproportionate collapse of a structure. Due consideration should be given to the situations during construction where the failure of a single element could lead to disproportionate or progressive (domino-type) collapse. To avoid disproportionate or progressive collapse, erection designers should consider— (a)
adequate strength and continuity of the structure and its parts; and
(b)
alternative load paths, whereby applied forces can be transmitted safely through the structure.
Structural continuity might rely on, among other things, moment, shear or tensile connection, depending on the kind of structural system employed.
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2.5 DESIGN FOR MANUFACTURE, HANDLING AND ERECTION 2.5.1 Factors applicable to self-weight of element
When determining the critical load or load combination for design, consideration shall be given to construction sequences and construction procedures. In the design for handling, transport and erection, the weight of the element shall be considered as a dead load (permanent action) in accordance with this Standard. The weight of the concrete element shall be multiplied by the appropriate factors as indicated in Tables 2.1 to 2.4. The appropriate factors shall be— (a)
at the time of lift-off from the casting bed, the suction factor and sling angle factor combined; and
(b)
after lift-off from the casting bed, the dynamic factor and sling angle factor combined and service life factor if applicable.
NOTE: The fac factors tors coul could d vary va ry at diff differen eren t stage s tagess of manu manufact fact ure, hand handlin ling g an and d er ection. ect ion.
The factors shall be used to determine the applied load at each lifting point and shall also be considered in the selection of the rigging. NOTE: This Thi s is i s indepe i ndependen ndentt to t o th e fa facto ctors rs consi c onsidere dered d in the select sel ection ion of tthe he ccrane rane.. ) d e t n i r p n e h w d e e t n a r a u g t o n y c n e r r u c t n e m u c o D ( 6 1 0 2 b e F 4 2 n o D T L Y T P A I L A R T S U A E K R U O R O G N I A L y b d e s s e c c A
C2.5.1
Consideration should be given to the use of A-frames or flatbed trailers during transportation. Additional care should be taken when using mobile lifting equipment for movement or installation of elements. The factor for transport over very rough ground may be higher in certain circumstances. Special consideration should be given to the following: (a)
Construction loads.
(b)
Handling and transport loads.
(c)
Erection loads.
(d)
Wind load on the braced elements.
(e)
Snow and seismic loads.
(f)
Pre-tensioned elements.
(g)
Thin or asymmetrical elements.
Ere ction Erecti on-loa loadd des design ign sho should uld con consid sider er var variat iation ionss to the loa loadd dis distri tribut bution ion dur during ing lif liftin ting, g, rotation and impact during placement. The effect of suction and adhesion at separation from the form or casting bed (lift-off) and dynamic and impact loading during transportation, erection and temporary support should be considered. The multiplying factors stated in this Clause assume the use of effective bond-breakers and release agents. Suction loads may vary according to the finish and the type of form or casting bed. Where the casting bed has a profiled or textured surface, the suction load factor may exceed 2 and will need to be considered in the design. Consideration should be given to the casting bed profile to ensure that adequate draw (slope) is provid pro vided ed to the fixed fix ed edg edges es of the forms for ms not str struck uck pri prior or to lilifti fting. ng. A min minimu imum m dra draw w of 1:12 is recommended. Dyn amicc loa Dynami loads ds gen genera erated ted dur during ing hand handlin lingg and transp tra nsport ort can be signif sig nifica icant nt and sho should uld be considered in the design of the lifting inserts and rigging system. These increases can range from 20% during handling by crane up to 100% during transportation. Dynamic loading should only be considered after release (lift-off) of the element from the casting bed. The increase in design load due to suction and impact are not cumulative. © Standards
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TABLE 2.1 SLING ANGLE FACTORS APPLIED TO THE ELEMENT AND LIFTING POINTS Angle
Sling angle factor
0
1.00
30
1.04
60
1.16
90
1.42
120
2.00
NOT ES: 1
Bending moments in the lifted element may increase with increasing sling angle.
2
For an example of the effects of the sling angle on the lifting inserts with a 10 t element, see Figure 2.1.
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30°
5.2 2 tt
55. 22tt
60° 6t
6t
90° 7t 7t
7t 7t 120°
10 tt
10 1 t
10 t load FIGURE 2.1 SLING ANGLE FACTOR
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TABLE 2.2 SUCTION FACTORS APPLIED TO THE ELEMENT AND LIFTING POINTS Suction condition
Suction factor
When calculating insert loads and bending moments at the point of element liftoff from a concrete casting bed with an effective bond-breaker
≥1.4
When calculating insert loads and bending moments at the point of element lift-
≥1.2
off from a smooth, oiled steel casting bed Other casting surfaces to account for the effects of suction and adhesion (e.g. form liners)
As appropriate
TABLE 2.3 DYNAMIC FACTORS APPLIED TO THE ELEMENT AND LIFTING POINTS (UNLESS VERIFIED BY OTHER MEANS) Means of transportation
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Dynamic factor
A stationary crane, including an overhead gantry crane, a crane standing on outriggers or a tower crane
≥ 1.2
Transport by truck on a prepared even surface
≥ 1.4
Tracked mobile lifting equipment travelling with the suspended load on a
≥ 1.7
prepared even surface (see Note 1) Non -tr ack acked ed mob mobile ile lif tin g e qui quipme pme nt (inclu (in cludin din g r ubb er-t yred ) ttrav ravell elling ing with the suspended load on a prepared even surface (see Note 1)
≥ 2.0
≥ 5.0
All mobile equipment travelling with the load suspended on unprepared uneven surfaces (see Note 1) NOT ES: 1
Mobile lifting equipment travelling with a suspended load shall be operated according to the manufacturer’s instructions, paying particular attention to the travelling speed and surface condition.
2
For a maximum travelling speed with a suspended load, see AS 2550.1.
TABLE 2.4 SERVICE LIFE FACTOR (To be read in conjunction with Clause 2.5.3.2) Application
Service life factor
All lifting and handling of prefabricated concrete elements during manufacture, delivery and installation prior to the completion of construction
1.0
Where the application of the element requires it to be lifted repetitively throughout its service life (e.g. temporary concrete barriers that are regularly repositioned)
1.6
Table 2.4
The application of the 1.6 factor is equivalent to increasing the WLL factor from fro m 22.25 .25 to 44.0, .0, as giv given en in AS 385 3850.1 0.1,, TTabl ablee 22.1. .1.
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2.5.2 Typical rigging configurations
Typical rigging configurations include but are not limited to the following: (a)
Flat lifting of elements.
(b)
Edge lifting of elements.
(c)
Face lifting of elements.
(d)
Mid-air rotation of elements (see Note 1).
The rigging system shall be designed to equalize loads on all lifting inserts, unless otherwise specified (see Note 2). The rigging system shall be designed to suit the spacing and layout of the lifting inserts. Load-equalizing lifting beams shall be of adequate length and capacity to suit the specified rigging system (see Note 3). When using multi-leg (three or more) fixed length slings connected to a common point, the full load shall be able to be taken by any two legs of the system. The included angle between the legs of a multi-leg sling shall not exceed 120° (see Note 4).
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The layout of the lifting points and the rigging configurations shall be designed to ensure stability of the element, without manual assistance that may place an operative in the drop zone, during all lifting and handling operations (see Note 5). NOTES : 1 Common rigging configurations are shown in Figures 2.3 to 2.6. 2 The rigging system will distribute equal loads to all lifting points only if the lifting inserts are equally located around the centre of gravity of the element being lifted. 3 A typical snatch-block for running rigging is shown in Figure 2.2. 4 An example of the included angle is shown in Figure 2.1. 5 This is not intended to exclude the use of guide ropes that may be used to control an element with the operative standing outside the drop zone.
C2.5.2
Three or four lifting inserts (see Figure 2.3) should be provided for lifting thin wide elements (e.g. large pit lids), which can become unstable if lifted from only two inserts placed in the face or the side of the element, as follows: (a)
For three inserts, insert locations for lifting aann element should be designed so that a line drawn between any two inserts does not pass through, or close to, the centre of gravity of the element. Ration Rat ionale ale:: The elemen ele mentt cou could ld rot rotate ate unc uncont ontrol rollab lably ly abo about ut the two ins insert ertss in lin linee with the centre of gravity if the sling attached to the third insert tried to go into compression and therefore became non-loadbearing.
(b)
For four inserts, insert locations for lifting an element should be designed so that a line drawn between any two adjacent inserts does not pass through, or close to, the centre of gravity of the element.
Lifts Li fts sho should uld be pla planne nnedd so tha thatt rot rotati ation on of sna snatch tch-bl -block ock sw swive ivels ls und under er loa loadd is not required. Where the snatch block is required to rotate, it should have thrust races or separate swivel bearings. An ins inspec pectio tionn and che check ck of riggin rig gingg sho should uld be per perfor formed med pri prior or to lif liftin ting, g, usuall usu allyy by the rigger in charge. A visual check should be carried out before each use to ensure that the collar pin is intact and that the collar has not become loose. Where sheave blocks with lockable clamp bolts are not available, care should be taken to ensure that the cheek plate clamp bolt is fully tightened and that rubbing and abrasion under load does not occur. www .st and ard s.o rg. au
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Alt hough Althou gh the loa loads ds in the slings sli ngs of run runnin ningg rig riggin gingg att attach ached ed to eac eachh ins insert ert are equ equal, al, the components of the sling load in the plane and perpendicular to the prefabricated elements might not be equal for each lifting insert because of the differing inclination of the slings to the elements. The sling loads, including their in-plane and perpendicular components, will also vary during rotation of the element. For elemen ele ments ts tha thatt are a re to be rot rotate ated, d, the use of liftin lif tingg ssyst ystems ems com compri prisin singg of o f 33,, 6, 9 or 12 lifting points should be avoided wherever possible due to the complex rigging required Run ningg rig Runnin riggin gingg is riggin rig gingg whe where re slings sli ngs pas passs thr throug oughh a she sheave ave blo block ck (ot (other herwis wisee kno known wn as a snatch block).
Ey e
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Thr ust fa c e
Collar
Clamp bolt Collar pin
Che e k pla te s
She a ve
FIGURE 2.2 TYPICAL SNATCH BLOCK
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Centre of gravity
Centre of gravity
(a) Despite four legs, the load is only d ist r ib u t e d o ve r t w o d ia g o n a lly opposed legs. The other two legs are r e q u ir e d t o p r o vid e st a b ilit y d u r in g t h e lif t . ) d e t n i r p n e h w d e e t n a r a u g t o n y c n e r r u c t n e m u c o D ( 6 1 0 2 b e F 4 2 n o D T L Y T P A I L A R T S U A E K R U O R O G N I A L y b d e s s e c c A
AS 3850.2:2015 3850.2:2015
(b) The load is equally distributed over four le g s u sin g lo a d e q u a liza t io n e q u ip me n t .
Pin n e d / H in g e d co n n e ct io n to allow free rotation
120°
120° 120°
Centre of gravity Centre of gravity (c) The load is equally distributed o ve r t h r e e le g s w h e n t h e lif t in g in se r t s a r e positioned equally around the centre of gravity and the legs are of equal length; however the design should only consider 2 le g s
(d) The load is equally distributed over four le g s u sin g a lo a d e q u a lisin g lif t in g b e a m
FIGURE 2.3 (in part) COMMON FLAT LIFTING CONFIGURATIONS
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Centre of gravity Packing material under chain (e) Alternate lifting arrangements with the load is distributed over two legs
) d e t n i r
p n e h w d e e t n a r a u g t o n y c n e r r u c t n e m u c o D ( 6 1 0 2 b e F 4 2 n o D T L Y T P A I L A R T S U A E K R U O R O G N I A L y b d e s s e c c A
Centre of gravity Packing material under chain (f) Alternate lifting arrangements with the load is distributed over two legs
Always attach hook or shackle through both top and diagonal wires
¼L
Packing material between units
Centre of gravity ¼L
Packing material under chain (g) Alternate lifting arrangements with the load is distributed over two legs per load. NO T E: T h i s t y p e of l i f t i n g r e q u i r e s t h e u s e of e q u a l le n g th slin g s a c r o ss a ll lo a d s so th a t th e lo a d s a r e le v e l. T h is f ig u r e d o e s n o t sh o w a p ig g y - b a c k e d lo a d .
(h) This method of lifting is only acceptable if tested in accorda nce with AS 3850.1. Despite four legs, the load is only distributed over only two diagonally o p p o s e d l e g s . Th e o t h e r t w o l e g s a r e required to provide stability during the lift. NO T E : L o c a t i on of l i f t i ng p oi nt s t o b e p e r m a n e n t l y m a rk e d o n t h e p a n el p r i o r to lifting
FIGURE 2.3 (in part) COMMON FLAT LIFTING CONFIGURATIONS
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C en en tr tr e o f g ra ra v it it y
) d e t n i r p n e h w d e e t n a r a u g t o n y c n e r r u c t n e m u c o D ( 6 1 0 2 b F e 4 2 n o D T L Y T P A I L A R T S U A E K R U O R O G N I A L y b d e s s e c c A
(i ) T he l oad i s di s tr ibuted over t wo le gs
AS 3850.2:2015 3850.2:2015
C en en tr tr e o f g ra r a v it it y
j) F j) t ar itrs tw o ohuald n gn w h et heeq ul aid nist d i nagn t le( ve l,otrhteh e in s se o ti tb f r o m t h e c e n t r e o f g r a vit y a n d t h e l o a d s in t h e slin g s w o u ld n o t b e e q u a l.
NOTES: 1
When flat lifting with three lifting points in a single plane with equal length slings, the centre of lift for the lifting points should be located in line with the centroid of the element, otherwise the sling and insert loads will be unequal and potentially unstable, with the load shared by only 2 slings.
2
When lifting on three points in any other configuration [e.g. (j) above], the rigging should be designed to ensure that centre of lift is in line with the centroid of the element, and take into consideration the desired erection orientation and stability. In this case the sling and insert loads will be unequal.
3
When fixed length inclined chains are connected to an element with inserts at a different level, it is difficult to ensure the element will ‘hang level’. Consideration should be given to inserting a pulley block into one leg so the level of the element can be adjusted.
4
When some inserts on an element are below its centre of gravity, consideration should be given to ensuring the element cannot roll sideways during lifting. Elements should never have all lifting inserts below the centre of gravity.
FIGURE 2.3 (in part) COMMON FLAT LIFTING CONFIGURATIONS
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Centre of g r a v it y
Centre of g r a v it y
P o in t o f r o t a t io n
) d e t n i r p n e h w d e e t n a r a u g t o n y c n e r r u c t n e m u c o D ( 6 1 0 2 b
M aa xxim M i m um s llin i ng a n gg lle e 6 0°
M aa xxim M i m uum m ss llin ing a n gg lle e 60°
P o in t o f r o t a t io n
( a ) T h e lo a d is d is t r ib u t e d o v e r t w o le g s u s in g a lif t in g b e a m ( f la t p a n e l r o t a t io n
( b ) T h e lo a d is d is t r ib u t e d o v e r t w o le g s .
f r o m h o r iz o n t a l t o v e r t ic a l) .
NO T E: A m a x i mu m r e c o m m e n d e d sl i n g a n g le o f 6 0 ° ( f l at p an el r o t at i o n f r o m h o r i zo n t al t o v er t i cal )
C ee nn tt r e o f g r a vv iitt y
P o in t o f
F e 4 2 n o D T L Y T P A I L A R T S U A E K R U O R O G N I A L y b d e s s e c c A
r o t a t io n
( c ) S in g le p o in t lif t ( c o lu m n r o t a t io n f r o m h o r iz o n t a l t o v e r t ic a l)
FIGURE 2.4 COMMON EDGE LIFTING CONFIGURATIONS
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AS 3850.2:2015 3850.2:2015
Minimum sling le ngth = 2 D
Minimum sling le ngth = C + 300 mm
C
D
(a)
( b) Minimum sling le ngth = 4.5 D or 4.5 E whic he ve r is the gr e a te r
Minimum sling le ngth = 3 C + D ) d e t n i r p n e h w d e e t n a r a u g t o n y c n e r r u c t n e m u c o D ( 6 1 0 2 b F e 4 2 n o D T L Y T P A I L A R T S U A E K R U O R O G N I A L y b d e s s e c c A
C
E
D D
Minimum sling length 3D
(c )
(d )
Minimum sling le ngth = 2 D
D
(e )
FIGURE 2.5 COMMON FACE LIFTING CONFIGURATIONS
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) d e t n i r p n e h w d e e t n a r a u g t o n y c n e r r u c t n e m u c o D ( 6 1 0 2 b F e 4 2 n o D T L Y T P A I L A R T S U A E K R U O R O G N I A L y b d e s s e c c A
18
1. L i f t - o f f
2. S p in u p
3. Disconnect and erect
FIGURE 2.6 MID-AIR ROTATION OF ELEMENTS
Figures 2.5 and 2.6
Specification of sling lengths is part of the erection design; however, the minimum shown in Figure 2.5 should be complied with. Dur ing mid During mid-ai -airr rot rotati ation on (see (se e Fig Figure ure 2.6), 2.6 ), the loa loads ds app applie liedd to the lif liftin tingg ins insert ertss var varyy depending on the relative position of the lifting inserts and crane lines. The load transferred to a single insert could exceed 75% of the total load. 2.5.3 Lifting inserts 2.5.3.1
General
Lifting inserts in accordance with AS 3850.1 shall be i ncorporated into prefabric ated elements to enable them to be lifted. NOTE: Rigging Rig ging confi configura guration tion exam example pless for pref prefabri abricat cated ed concret conc retee element ele mentss are shown in Figures 2.3 to 2.6.
The actual locations of the lifting inserts shall be determined according to the— (a)
number of lifting inserts, their spacing and edge distances;
(b)
centre of gravity;
(c)
method of lifting (face or edge);
(d)
mass, size and shape of the prefabricated concrete element and presence of openings and cut-outs;
(e)
structural capacity of the prefabricated concrete element;
(f)
strength of the prefabricated concrete element at the time of lifting;
(g) (h)
capacity of the lifting inserts; and direction of load (shear, tension or combined shear/tension).
NOTE: For an eexamp xample le of shea shearr and a nd ttensi ension on loads l oads,, s ee F igure igur e 2. 2.7. 7.
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AS 3850.2:2015 3850.2:2015
When a prefabricated concrete element is to be tilted about an edge by using lifting inserts that are placed in the face of the prefabricated concrete element, the geometric centre of the face-lift inserts shall be above the prefabricated concrete element’s centre of gravity. Face-lifted prefabricated concrete elements shall be designed to hang not more than 10° from the vertical. If this is not possible, consideration shall be given to using edge-lifting or a combination of face-lifting and edge-lifting. If the lifting system specified contains component reinforcement, it shall be installed and verified in accordance with the lifting system manufacturer’s specification. Such validation shall be documented. NOTE: For typ typical ical liftin lif ting g inser i nser ts, see Figu res 2.8(A) 2.8( A) and for an exa example mple of tens ion bar attache att ached d to an insert, see Figure 2.8(B).
C2.5.3.1
Lifting inserts are specially designed and manufactured with a controlled strength and ductility. They should be specified and installed in accordance with the manufacturer’s specifications, including component reinforcement to AS/NZS 4671, for the direction of the applied load. When a designer selects lifting inserts, consideration should be given to the applied lifting load (see Clause 2.5.1) at all stages of construction. ) d e t n i r p n e h w d e e t n a r a u g t o n y c n e r r u c t n e m u c o D ( 6 1 0 2 b F e 4 2 n o D T L Y T P A I L A R T S U A E K R U O R O G N I A L y b d e s s e c c A
A des design igner er sho should uld con consid sider er whe where re to pla place ce liftin lif tingg ins insert ertss and con consid sidera eratio tionn sho should uld als alsoo be given to slenderness and whether there is a need for strongbacks to be used, partic par ticula ularly rly if the pre prefab fabric ricate atedd con concre crete te elemen ele mentt has lar large ge or awk awkwar wardly dly loc locate atedd openings. The centre of gravity of the element is essential to the lifting design to ensure that the element is lifted as intended. The anchorage capacity of the lifting point is affected by— (a)
method of installation;
(b)
proximity to the edges;
(c)
proximity to the holes, recesses or edge rebates;
(d)
proximity to other loaded lifting devices;
(e)
the concrete thickness;
(f)
the concrete strength at lifting;
(g) (h)
the embedment depth; the presence of cracks;
(i)
the direction of load, for example shear and tension (see Figure 2.7);
(j)
proximity of reinforcement or prestressing tendons; and
(k)
additional reinforcement specified by the insert supplier.
Not e tha Note thatt any reinfo rei nforce rcemen mentt not spe specif cified ied by the ins insert ert sup suppli plier er can cannot not be ass assume umedd to increase capacity unless verified by testing in accordance with AS 3850.1. Bars placed around the foot of the lifting insert typically provide no additional lifting capacity to the insert [see [s ee Figure 2.8(A)]. An example of the cor correct rect connection of component reinforcement to an insert is given in Figure 2.8(B). Welding of reinforcement to lifting inserts, brace inserts or ferrules should not be carried out. Technical specifications of the lifting inserts, including make, type and working load limit (WLL), should be provided with the lifting inserts and a copy held on the project site. www .st and ard s.o rg. au
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Lifti Li fting ng insert ins erts, s, bra brace ce insert ins ertss and ferrul fer rules es sho should uld be spe specif cified ied on the des design ign drawin dra wings gs as to the type (e.g. cast-in or post-installed expansion anchor) and the capacity. They should not be changed without prior approval from the prefabricated concrete element designer. Lifting inserts within the prefabricated concrete element should be specified as cast-in inserts. Where cast-in inserts are omitted or after casting are found to be unusable, approval from the designer to use other types should be obtained before installation. 2.5.3.2
The re-use of the lifting inserts
The re-use of lifting inserts is permissible for lifting and handling of precast concrete elements during all stages of manufacture, delivery and installation prior to the completion of construction. Where re-used, a service life factor of 1 shall be used. Where the application of the prefabricated concrete element requires that it be lifted repetitively during its service life, a service life factor of 1.6 shall be used (see Table 2.4).
Ele ments Elemen ts are typ typica ically lly lifted lif ted mor moree tha thann onc oncee bet betwe ween en man manufa ufactu cture re and fin final al positi pos ition. on. The pri princi ncipal pal fac factor torss tha thatt may lim limitit the rere-usa usabil bility ity of lif liftin tingg ins insert ertss in these the se types of elements are as follows: C2.5.3.2
) d e t n i r p n e h w d e e t n a r a u g t o n y c n e r r u c t n e m u c o D ( 6 1 0 2 b
(a)
Overloading of the insert past its WLL.
(b)
The condition of the concrete at time of lift.
(c) (d)
Deformation and wear of the lifting insert. Corrosion of the lifting insert.
(e)
Other actions that have a physical impact on the insert’s material properties or the insert shape (i.e. welding to the insert).
Pro vided Provid ed the liftin lif tingg insert ins ertss have hav e nev never er bee beenn loa loaded ded pas pastt their the ir WLL WLL,, the there re is no physic phy sical al deformation or corrosion of the insert, the concrete is still sound and in its original state, and the loads are and have been applied at low speeds and at low frequency, the lifting inserts will continue to perform their design task. Special requirements detailed in Claus Clausee 2.5.1 apply for concrete el elements ements that are designed to be repetitively lifted during their design life (e.g. temporary road barriers).
F e 4 2 n o D T L Y T P A I L A R T S U A E K R U O R O G N I A L y b d e s s e c c A
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AS 3850.2:2015 3850.2:2015
Pa ne l r ota tion
Tilting axis
Casting bed SHE AR LOAD
Edge lifting insert She a r ba r (if specified)
TE NSI ON LOAD
) d e t n i r p n e h w d e e t n a r a u g t o n y c n e r r u c t n e m u c o D ( 6 1 0 2 b
Te nsion ba r (if specified)
NOTE: If shear load lifting is required in the opposit oppositee direction to the initial lift, then shear bars may be required on both faces.
FIGURE 2.7 SHEAR AND TENSION LOADS IN EDGE-LIFTED ELEMENTS
F e 4 2 n o D T L Y T P A I L A R T S U A E K R U O R O G N I A L y b d e s s e c c A
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=
= ) d e t n i
FIGURE 2.8(A) EXAMPLES OF REINFORCEMENTS THAT HAVE NO EFFECT ON THE CAPACITY OF LIFTING INSERTS
r p n e h w d e e t n a r a u g t o n y c n e r r u c t n e m u c o D ( 6 1 0 2 b F e 4 2 n o D T L Y T P A I L A R T S U A E K R U O R O G N I A L y b d e s s e c c A
Tension bar is attached to an insert in accordance with the manufacturer’s specifications.
FIGURE 2.8(B) TENSION BAR
2.5.4 Cast-in and post-installed brace inserts
Brace inserts shall be in accordance wit h AS 3850.1 and designed to resist all loads transferred by the brace to the fixing, including loads dependent on the angle of bracing and prying pryi ng forces for ces depend dep endent ent on the geo geomet metry ry o off the t he brace bra ce foot. foo t. NOTE: Figu re 2.9 2 .9 illust ill ustrat rates es the effect effe ct of brac bracee angle angl e and brac bracee foot geom geometr etry y on the tens ion or compression forces into a brace fixing.
Where elements are lifted with braces attached, brace inserts in the elements shall be positi pos itione oned d so s o the t he crane cra ne riggin rig ging gw will ill not foul fou l the t he brace brac e duri d uring ng lif liftin ting. g. Where possible, braces shall not obstruct the erection of subsequent construction. Where unavoidable, a procedure shall be nominated and followed. The permanent structural elements that will provide in-service stability to the element (such as roof steelwork) shall be installed prior to removal of the braces, in accordance with Clause 6.2.
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AS 3850.2:2015 3850.2:2015
C2.5.4
In general, brace inserts should not be placed closer than 300 mm to the edge of the element (to avoid edge reduction factors), footing or other bracing support, unless specifically designed otherwise. Where possible, for face-lifted wall element, brace inserts should be on the same face of the element as the lifting inserts. Bra ce insert Brace ins ert cap capaci acitie tiess are se sensi nsitiv tivee to the sam samee fac factor torss as lif liftin tingg ins insert ertss giv given en in C2.5.3.1 Items (a) to (k). Bra ce insert Brace ins ertss abo above ve the line lin e of attach att achmen mentt of roo rooff ste steelw elwork ork are an exa exampl mplee of obstruction of subsequent construction. The durability of brace inserts should also be considered, particularly when exposed to the elements.
Br a ce V T
Pin co n n e ct io n o f b r a ce to brace foot
HT
B
Br a ce in se r t
) d e t n i
F e 4 2 n o D T L Y T P A I L A R T S U A E K R U O R O G N I A L y b d e s s e c c A
HT
Br a ce f o o t
A
r p n e h w d e e t n a r a u g t o n y c n e r r u c t n e m u c o D ( 6 1 0 2 b
T
C
V T
D
I d e a l b r a ce a n g le o f in clin a t io n D ime n sio n s o f b r a ce f o o t r e q u ir e d t o ca lcu la t e b r a ce in se r t lo a d
N C =
T ×
Br a ce ’s a xis p a sse s t h r o u g h xin g h o le ce n t r e - lin e o n u n d e r sid e o f b r a ce ( Bo lt t e n sio n = V T )
V T
e cc
N C =
C
Bo lt t e n sio n : = V T + N C
V T HT
T ×
e cc
D
HT
T c c e
NC
Brace inclination below ideal angle LEGEND: V T = = N c = T H T = ecc =
T
c e c
Bo lt t e n sio n : = V T + N C NC
Brace inclination above ideal angle
vertical component of the tension reaction load tension in the line of the brace horizontal component of the tension eccentricity
NOTES: 1
A rigid base plate is assumed.
2
Dimensions A, B, C and D can be obtained from the brace supplier’s product information.
3
The bracing loads may be tension or compression.
FIGURE 2.9 EFFECT OF BRACE ANGLE AND BRACE FOOT GEOMETRY ON TENSION TENSION IN BRACE FIXING
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2.5.5 Cast-in fixing and brace inserts (ferrules) 2.5.5.1
General
Cast-in inserts, such as threaded inserts, weld plates or brackets, shall be designed and specified by an engineer, and shall be installed according to the element shop drawings. Where possible, to minimize the chance of error, fixings shall be standardized for all prefab pre fabric ricate ated d concre con crete te elemen ele ments ts on an ind indivi ividua duall pro projec ject. t. Where Whe re perman per manent ent fixing fix ingss are also als o intended to be used for the attachment of temporary supports, designers shall give consideration to all load cases. Any fixings or fixing method, in particular impact-driven fixings, including explosive charge-driven fixings, shall not be used if their use will compromise the strength of a prefabricated concrete element. NOTE: Forces Forc es applied appl ied to fixi fixing ng inse inserts rts are determi dete rmined ned by the in-s ervi ervice ce desi designer gner.. Ther efore efore,, their the ir determination is outside the scope of this Standard; however, all fixings required for the permanent structure should be shown on the architectural or structural drawings, as appropriate.
2.5.5.2
Specifying inserts
The in-service designer may either specify— ) d e t n i r p n e h w d e e t n a r a u g t o n y c n e r r u c t n e m u c o D ( 6 1 0 2 b e F 4 2 n o D T L Y T P A I L A R T S U A E K R U O R O G N I A L y b d e s s e c c A
(a)
the type and size of the permanent fixing inserts; or
(b)
the loads the inserts are required to resist.
2.5.5.3
Specifying loads
Where loads are specified, it shall be made clear— (a)
in which direction they act; and
(b)
whether the specified loads are factored or unfactored.
2.5.5.4
Selection and location of inserts
When selecting inserts to take specified loads, the load capacity of the insert shall have been determined by testing with due allowance for the following possible areas of difference between the test and the proposed insert location: (a)
Concrete strength.
(b)
Element thickness.
(c) (d)
Fixing length. Edge distance.
(e)
Proximity of fixings to one another.
(f)
Component reinforcement.
(g)
Ductile behaviour of the insert steel.
Factors affecting permanent or temporary fixing selection include the following: (i)
Durability (finish of the insert).
(ii)
Performance in fire.
All cast-in inserts required for in-service and erection shall be shown and specified on the manufacture (shop) drawings. Where (e.g. drilled in or chemical anchors) element are used,depth their and locations shall bepost-installed verified priorinserts to casting, with respect to edge distance, local reinforcement, as appropriate. NOTE: The loc locati ation on of o f po postst-inst install alled ed inse inserts rts is not shown on tthe he manu manufac facture turer’s r’s (sho (shop) p) drawi d rawings. ngs. © Standards
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AS 3850.2:2015 3850.2:2015
C2.5.5.4
Elevated temperatures may reduce the capacity of anchors, in particular chemical anchors. Supplier’s data should be consulted.
2.5.6 Wind loads
Wind loads on elements that are temporarily braced shall be determined from AS/NZS 1170.2:2011 using annual probabilities of exceedance based on Tables F1 and F2 of Appendix F of AS/NZS 1170.0:2011, and when comparing with the WLL of temporary braces, wind load shall be divided by 1.5 to convert to the working load. Where the ‘drop zone’ of the element is within the building site, a minimum importance level 2 in accordance with AS/NZS 1170.2:2011 shall be used. Where the drop zone of the element is beyond the building site boundary, the importance level of the adjacent property shall be considered if the importance level of the adjacent site is greater than 2. NOTES : 1 For importance levels, see Table F1 of Appendix A of AS/NZS 1170.0:2002. 2 The design terrain category, region and design wind speed should be included in the erection documentation.
C2.5.6 ) d e t n i r p n e h w d e e t n a r a u g t o n y c n e r r u c t n e m u c o D ( 6 1 0 2 b e F 4 2 n o D T L Y T P A I L A R T S U A E K R U O R O G N I A L y b d e s s e c c A
For elements with potential to cause progressive collapse by falling on other elements, or falling from height onto other structure, the designer should consider a more conservative annual probability of exceedance.
When significant delays in construction occur, the designer of the temporary works may need to be informed to ensure the design assumptions are still valid. This can be of partic par ticula ularr rel releva evance nce for pro projec jects ts in sea season sonal al are areas as (e.g. (e. g. cyc cyclon lonic ic are areas) as) whe where re the initial intention was to construct in non-cyclonic periods. This Standard incorporates the use of several items of equipment that have their capacity stated as WLL. Therefore, for consistency, WLL has been adopted throughout this document. When AS/NZS 1170.2 changed from working loads to limit states, the load factor for conversion between the two was 1.5. That value has been retained in this Standard. Site huts, amenities and evacuation/refuge areas should ideally be located outside of the drop zone. 2.5.7 Strength specification of concrete
The concrete strength shall be specified to provide adequate strength at the time of lifting— (a)
to develop the required design capacity of any lifting insert or device; and
(b)
to factor in adequate flexural tensile strength.
NOTE: The requirem requ irem ents ent s for f or in-s in-servi ervice ce load loading, ing, durab ility ili ty and any construc cons tructio tion n requi r equirem rements ents such as workability need to be considered when specifying concrete strength.
2.5.8 Design of elements for manufacture, transport and and erection
Bending stresses in precast elements imposed by their self-weight (factored only as required by Clause 2.5.1) during handling, transportatio n and erection, and determined with due consideration of the rigging configurations specified, shall be resisted by— (a)
the flexural tensile strength of the concrete at the time of the activity, which shall be limited to not greater than
0.41
f ′c.age ;
(b)
in accordance with reinforced concrete design methods based on the assumption of a cracked section; or
(c)
a combination of Items (a) and (b).
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When designing on the basis of a c racked section [Item (b)], due consideration shall be given to control of crack widths as required for the element to meet aesthetic and durability requirements in its in-service life. When designing on the basis of Item (c), the design shall stipulate the extent of reinforcement from zones designed assuming a cracked section into zones that are designed as an uncracked section. C2.5.8 Generally, prefabricated concrete elements will be designed for erection, assuming they are usually uncracked and for the appropriate loads in the permanent structure on the basis of reinforced concrete design. Significant cracks in prefabricated concrete elements that exceed 0.3 mm in width and occur during lifting are difficult to repair and may be detrimental to serviceability issues (e.g. corrosion).
Wall panels to be transported to site should include at least one continuous perimeter reinforcing bar, lapped as required and cogged at the corners of typically 12 mm or 16 mm diameter bars. Add itiona Additi onall rei reinfo nforce rcemen mentt may be req requir uired ed in con concre crete te elemen ele ments ts whe where re ere erecti ction on str stress esses es exceed stresses arising from in situ loads. ) d e t n i r p n e h w d e e t n a r a u g t o n y c n e r r u c t n e m u c o D ( 6 1 0 2 b e F 4 2 n o D T L Y T P A I L A R T S U A E K R U O R O G N I A L y b d e s s e c c A
To accommodate forces during handling, transportation and erection, further reinforcement may be required. Furthe Fur therr addi a dditio tional nal rei reinfo nforce rcemen mentt sshou hould ld be con consid sidere eredd ffor or the fol follow lowing ing con condit dition ions: s: (a)
Near the base of the concrete element to resist stresses that arise from thermal and shrinkage movements while the concrete element is supported only on the levelling shims.
(b)
At the edges and around openings in the concrete element to resist thermal and shrinkage stresses, and to prevent cracking due to concrete element mishandling.
(c)
Where there is a possibility of load reversal due to mishandling that could occur during transport or erection.
Add itiona Additi onall rei reinfo nforce rcemen mentt or str strong ongbac backs ks sho should uld be pro provid vided ed whe where re the max maximu imum m flexur fle xural al ten tensil silee str stress ess in con concre crete te elemen ele ments ts exc exceed eedss the lim limits its rec recomm ommend ended ed in techni tec hnical cal Standards or 0.41√f′c, whichever is the lesser. 2.5.9 Design of temporary bracing for vertical elements
Where prefabricated elements are erected without sufficient horizontal stability at the point of installation, they shall have additional appropriate measures designed and installed until the required restraint is afforded by the completed structure. The temporary restraint system may be designed as either primary bracing or a combination of primary and secondary bracing components. NOTE: For an iillu llustra stratio tion n of prim ary and secondar seco ndary y br acing aci ng eeleme lements nts,, ssee ee Figure Figu re 2.10.
Factors for the design of temporary support for vertical or near-vertical elements shall comply with the following: (a)
Wind forces in temporary braces shall be determined in accordance with Clause 2.5.6.
(b)
Additional superimposed lateral load shall be considered in the bracing design for vertical concrete elements that support horizontal flooring elements, particularly for unpropped flooring construction. NOTE: For requirem requ irem ents for superimp supe rimpose osed d lo loads, ads, see Clause Cla use 5.2.
(c)
© Standards
Lateral pressure from the in situ pour shall be considered in the bracing and base connection design for vertical elements acting as formwork for the adjacent in situ construction, such as an in situ deep beam abutting a concrete panel. Australia
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(d)
The overall stability and the sequence of element erection shall be checked to ensure that, at any stage, the risk of a mechanism leading to progressive collapse of the elements is minimized.
(e)
Except as provided for in Item (g), each element shall be supported by a minimum of two braces of adequate capacity.
(f)
Narrow Nar row elemen ele ments ts shal l be be b brac raced ed in two orthog ort hogona onall dire d irecti ctions ons..
(g)
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AS 3850.2:2015 3850.2:2015
Where designed replaced by— and specified on the shop drawings, one or more braces shall be (i)
equivalent supports, such as corner supports, main structure and box structures; or
(ii)
a single fixed-length robust brace purposely designed for the specific application.
(h)
Fixings at each end of the brace shall be adequate to transmit the calculated force in the brace into the surrounding concrete or steel. The type of fixing or the required capacity of the fixing shall be nominated on the manufacture (shop) drawings.
(i)
The end of a brace not connected to the element shall be fixed to a member or system capable of resisting the calculated force in the brace.
(j)
The brace feet shall be of a type designed to prevent sliding disengagement from the
(k)
(l)
(m)
insert after installation. The effective length of a main brace may be reduced by the inclusion of secondary bracing components to afford lateral restraint at a location along its length, provided any such secondary bracing shall restrain the main brace in all directions of possible buckling. Calculation of loads applicable to components that provide buckling restraint shall comply with the requirements for parallel compression braced members given in Clause 6.6.3 of AS 4100:1998, regardless of the materials used in the secondary bracing. The capacity and performance of any component or system of components to act as a buckling restraint (as secondary bracing) and their required connections shall be verified by te sting the loads calculated by Item (k) above i n accordance with Paragraph A10 of Appendix A of AS 3850.1:2015, (Additional testing for braces). A test report shall be provided with the component.
(n)
The braceorstructure shall be adequate to support the prefabricated elements including concrete steel. The bracing requirements shall be fully documented in the erection documentation. NOTE: The shop draw drawings ings and the erec erection tion docum entati ent ation on sshoul hould d be coord coordinat inated. ed.
(o)
Where elements are braced to other temporarily braced elements, the system shall be designed to provide adequate temporary support to avoid the potential for progressive and/or disproportionate collapse.
(p)
The design of the brace layout and erection sequence, particularly where wall panels are designed to abut at corners, shall ensure that during erection of the second corner panel pan el the braces bra ces are placed pla ced withou wit houtt fou foulin ling g the braces bra ces of the first fir st erecte ere cted d panel. pan el. Consideration shall be given to the outward rotation of the brace of the second panel.
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C2.5.9
A bracing system is an arrangement of temporary supports, which provides stability to prevent a prefabricated concrete element from overturning. Common types of bracing systems include the following: (a)
Primary bracing only (individual, clear-spanning main braces).
(b)
Primary and secondary bracing (main braces with dual secondary knee braces).
(c)
Primary and secondary bracing (main braces with single secondary knee brace, pluss cros plu c ross-l s-laci acing, ng, in-pla in- plane ne diagon dia gonal al or end bra braces ces). ). (d) Primary and secondary bracing (main braces with single secondary knee brace and laced together as a deep truss). Eac h typ Each typee of bra bracin cingg pre presen sents ts a differ dif ferent ent str struct uctura urall for form m to wit withst hstand and the loa loadd cas casee of bracing compression and any onset of buckling behaviour by manipulating the slenderness of elements. The design of temporary bracing systems should account for the behaviour of all components and their connections within the specified system, and clearly detail the intended layout, material specification and installation requirements, allowing for any erection staging.
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For win windd load l oading ing,, ssee ee Cla Clause use 2.5 2.5.6. .6. The cho choice ice of the ret return urn per period iod for the win windd lload oad on braced elements should be reviewed in terms of the likelihood of high winds due to the season while the elements are temporarily braced and, in terms of the length of time, the elements are in the braced position. Par ticula Partic ularr con consid sidera eratio tionn nee needs ds to be giv given en to the str streng ength th of bra brace ce sup suppor portt elemen ele ments ts at the time of bracing, especially isolated footings. The use of a single brace should be avoided where possible; however, where single braces are used (e.g. on narrow elements), care needs to be exercised in preventing out of balance loads, which might rotate the element about the brace and cause collapse. Precau Pre cautio tions ns sho should uld be tak taken en to pro protec tectt brac b races es fro from m iimpa mpact ct loa loads. ds. If the upp upper er attach att achmen mentt poi point nt of the bra braces ces is below bel ow the cen centre tre of mas mass, s, spe specia ciall car caree should be taken in the erection design, including consideration of the base restraint. The design and installation of skew braces (i.e. braces not perpendicular to the element in plan) need to be carefully reviewed to consider any induced lateral and torsional forces for ces ont ontoo tthe he elemen ele ments ts.. Braces Bra cesricate are int edt pri toor res resist anyorpora pre predic dictab table le o loa loads tha that t ent canstr des destab tabili ze ethe pre prefab fabric atedd intend elemen eleended ment prior to ist its inc incorp oratio tion n int into the dsper perman manent struct ucture ure. .ilize Som Some of the likely loads are wind loads and construction loads. Where more than two braces are provided, the erection engineer will need to consider how the loads are apportioned to the braces. Connecting plates between elements are sometimes designed purely to facilitate alignment. Such plates should not be assumed to be a substitute for braces, unless otherwise specified on the manufacture (shop) drawings. For mwork Formwo rk pro props ps and fra frames mes are not sui suitab table le elemen ele ments ts to be use usedd to res resist ist hor horizo izonta ntall loads on prefabricated elements. Consideration should be given to multiple rows of bracing on tall slender elements. This would include consideration of the height from floor to braces, the height between braces, and the cantilever height above the top brace. For panels with the ratio of brace height to thickness exceeding 50, two levels of braces might be required.
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Br a c e point
Va r i e s a cc or di ng to de sign r e quir e me nts typic a lly two-thir ds he ight
Main brace (minimum two pe r pa ne l)
(a) Primary bracing of elements (where loads are less than the WLL)
Cr oss-la c ing ( should be c ontinuous) la p ove r ma in br a c e s ) d e t n i
r p n e h w d e e t n a r a u g t o n y c n e r r u c t n e m u c o D ( 6 1 0 2 b e F 4 2 n o D T L Y T P A I L A R T S U A E K R U O R O G N I A L y b d e s s e c c A
M a in br a c e
Kne e br a c e D ia gona l br a c e s in pla ne of ma in br a c e s or e nd br a c e s a t e a c h e nd of cross-bracing
(b) Secondary bracing of elements (where additional load capacity is required)
FIGURE 2.10 (in part) PRIMARY AND SECONDARY SECONDARY BRACING OF ELEMENTS
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NOTE: Where only one brace in each direction is possible, special precautions should be taken to protect those braces from impacts.
(c) Bracing of columns and thin elements
FIGURE 2.10 (in part) PRIMARY AND SECONDARY SECONDARY BRACING OF ELEMENTS
2.5.10 Design of temporary propping for horizontal elements
Where vertical temporary support is provided, robust lateral stability or a method of fixing the temporary support shall be provided to ensure the temporary support remains stable during construction. The following factors shall be considered in the design of temporary support for horizontal elements: (a)
The self-weight of the prefabricated element.
(b)
Any imposed load or load transferred onto the installed prefabricated element while in its temporary condition, which may include actions from temporary bracing of vertical elements.
(c)
The weight of any concrete topping or screeds while in the temporary condition.
(d)
The live load allowance for construction work occurring while the element is in the temporary propped state is in accordance with AS 3610.1 or other calculated values, and nominated on the design drawings.
(e)
© Standards
Whether the prefabricated concrete element is capable of supporting its own weight pluss the plu t he loads loa ds l ist isted ed above. abo ve. Australia
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(f)
That the structure below is capable of supporting the horizontal elements.
(g)
The propping is adequately braced for lateral loads.
AS 3850.2:2015 3850.2:2015
NOTES : 1 The temporary vertical support of prefabricated elements may or may not need to accommodate the self-weight of the element. Some prefabricated elements might be designed to require back propping for the applied load of the weight of a concrete screed only, for example to reduce deflection for the in-service condition. 2 Care should be taken when erecting prefabricated concrete elements on steel beams, which may not have adequate torsional restraint and will deflect elastically, resulting in possible problems in lining and levelling of prefabricated concrete elements. 3 When vertical precast concrete elements are erected on post-tensioned concrete floors which are subsequently stressed, allowance will need to be made for the relative movement of the floor in relation to the final position of the vertical element.
C2.5.10
Propping systems should allow for possible changes to the distribution of loads during the construction process. Where beams are post-tensioned after erection, the stressing process will change the shape of the member, thereby reducing the load on some props/frames and increasing the load on others. This particularly applies where the stressing induces a camber into the beam, which can lift the beam off props/frames at midspan, transferring the entire load to the props/frames at the ends.
) d e t n i r p n e h w d e e t n a r a u g t o n y c n e r r u c t n e m u c o D ( 6 1 0 2 b e F 4 2 n o D T L Y T P A I L A R T S U A E K R U O R O G N I A L y b d e s s e c c A
Pro ps and frames Props fra mes are tem tempor porary ary com compon ponent entss sup suppor portin tingg loa loads ds tha thatt pro produc ducee compression forces in the props and frames. Where the seating for precast beams cannot transfer loads during construction, the beams should be propped at each end to carry the full load. Where beams are to have floor systems placed on them prior to the beams being fully built into the structure, allowance should be made for uneven loading on the beam during construction. With floor units placed only on one side of a beam, additional temporary propping may be required to each edge of the beam. Steel beams that are end-supported on web cleats are particularly vulnerable to temporary eccentric loading. Support of prefabricated elements on structural steel beams demands special consideration of the compression flange restraint available to the steel beam during the construction phase and prior to integration into the final structure. Where required, all temporary propping should be in place and fully braced prior to commencement of erection of any prefabricated elements. Unless specifically detailed otherwise, temporary propping should provide full support to all construction loads, including the full self-weight of the completed floor system and possible local concentrations of load during construction. Construction loads may include mobile plant, reinforcing steel, material storage or excess concrete. Subject to the safe work method statement, it may be satisfactory to erect temporary props pro ps and fra frames mes after aft er the pre precas castt floo f loorr unit u nitss are a re in place, pla ce, and for the pro props ps and frames fra mes to take only a portion of the full construction load. Pro ps and frames Props fra mes should sho uld be ver vertic tical al and the theyy sho should uld als alsoo be bra braced ced to pre preven ventt side-sway of the whole assembly and the buckling of individual props. Precau Pre cautio tions ns sho should uld be tak taken en to pro protec tectt prop p ropss and a nd frames fra mes fro from m iimpa mpact ct loa loads. ds. Props Pro ps and frames fra mes should sho uld be ade adequa quatel telyy sea seated ted,, levell lev elled ed and cap capabl ablee of tra transf nsferr erring ing the ful full l loa loadd deflection throug thr oughh wha whatev er str struct ucture ure the theyy are bea bearin ringg onin and int intoo the ground und wit without hout adverse or tever settlement. Geotechnical advice addition to gro a geotechnical report may be required.
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2.5.11 Slenderness 2.5.11.1
General
Slender elements or parts of elements that are placed in direct or flexural compression during the handling and erection process may be subject to lateral buckling. This shall be considered in the erection design. 2.5.11.2
Size and shape of concrete elements
Slenderness and stability are major considerations in the design of pre-fabricated concrete elements. They shall be considered for the manufacture, handling, storage and erection phases pha ses of the constr con struct uction ion work. wor k. NOTE: Slender Sle nderness ness and stabil sta bility ity for in-servi in-s ervice ce condi tion shou should ld be addre addressed ssed by the in-s ervi ervice ce designer.
When determining the size and shape of concrete elements, consideration shall be given to the following:
) d e t n i r p n e h w d e e t n a r a u g t o n y c n e r r u c t n e m u c o D ( 6 1 0 2 b e F 4 2 n o D T L Y T P A I L A R T S U A E K R U O R O G N I A L y b d e s s e c c A
(a)
Size, capacity and arrangement of crane(s) that will undertake lifting and erection.
(b)
Manufacturing restrictions.
(c)
Location and proximity of overhead power supplies.
(d)
Access to and around the workplace.
(e)
Bracing, propping and grouting requirements.
(f)
Transport restrictions.
C2.5.11
Inclined slings attached to lifting inserts can cause compression, or a combination of bending and compression in an element. Thin elements transported to site on A-frames and rotated through 90° on site may have significant compression in their top edge (as transported) during rotation. Longer slings or a two-crane lift is a possible solution.
Edg e-lift Edge-l ifted ed elemen ele ments ts lifted lif ted from fro m a single sin gle hoo hookk wit withou houtt a lif liftin tingg beam bea m cou could ld als alsoo hav havee compression and bending induced into element edge in which the lifting inserts are cast. 2.5.12 Supports
When initially erected, elements shall be designed to sit on only two localized shimming poi nts.. T points The he ele men mentt and the foo footin tings gs shal l be be d desi esigne gned d tto o carr c arry y tthe he forces for ces from fro m t he locali loc ali zed supports, taking into account normal construction tolerances. To ensure the known distribution of load when elements are initially erected, they shall be supported on bearing pads, shims or bearing strips as follows: (a)
Columns—(one shim might be adequate).
(b)
Thin element elements [e.g., wall elements, facades and narrow beams (laterally braced)]—two shims only.
(c)
Wide horizontal elements (e.g., stair landings)—three shims only (where shims are required).
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C2.5.12
By specifying the locations of the shimming positions beneath elements, the designer can control where the weight of the elements will be supported. Construction tolerances are usually such that multiple shimming will not distribute the elements weight to its support in a predictable manner, since any two of the shims are likely to support most of the load. After erecting the elements, the addition of further shimming points poi nts or gro grouti uting ng ben beneat eathh the elemen ele ments ts cou could ld ser serve ve to red redist istrib ribute ute loa loadd fol follow lowing ing settlement beneath the original shimming points or additional loading of the elements. These points are particularly relevant to the design of strip footings or thickened slabon-ground edges to support elements. Construction tolerances of discrete element supports should be considered. For example, it is unlikely that adjacent ends of two elements can be supported on a single pierr of less pie les s tha thann 750 mm diamet dia meter. er. For pie piers rs on bou bounda ndarie ries, s, the imp implilicat cation ionss of the combined effect of tolerances and eccentric loads have to be considered and usually result in the need for pier/pile caps or transfer beams. Where two wall elements land on a discrete support, the load eccentricities that occur during construction—because one element has to be erected before the other—can sometimes be a critical load case in design. 2.6 JOINT WIDTHS ) d e t n i r p n e h w d e e t n a r a u g t o n y c n e r r u c t n e m u c o D ( 6 1 0 2 b e F 4 2 n o D T L Y T P A I L A R T S U A E K R U O R O G N I A L y b d e s s e c c A
Joint widths shall be specified in the drawings. The width of joints or gaps between adjacent and between and the main structure, shall sufficient to maintain elements, the designed positionselements and alignments during erection, andbe accommodate tolerances and the expected movements during in-service life. When determining the joint width and selecting the joint filling materials, consideration shall be given to the combined effect of— (a)
thermal and shrinkage movement of elements;
(b)
fire resistance level required (if any);
(c)
acoustic level required (if any);
(d)
weather resistance;
(e)
structural movements;
(f)
dimensional tolerance of elements; and
(g)
element location tolerance.
Unless otherwise specified, joint widths between adjacent elements shall be not less than the following: (i)
Joints with flexible sealant ............................................ .................................. 15 mm.
(ii)
Mortar or grouted joints ........................................................................ .......... 20 mm.
(iii)
In situ concrete infill .............................................................................. ....... 150 mm.
C2.6
A method of achieving this is with an appropriate sealant supported by a round closed cell backing rod. The final geometry of the sealant should be as per the manufacturer’s specification.
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2.7 FOOTINGS 2.7.1 Permanent footing for the support of elements
The design of footings for prefabricated elements shall take account of the following: (a)
When prefabricated elements are initially erected, their self-weight will bear on localized shimming points (see Clause 2.5.12). C2.7.1(a)
This is particularly relevant prefabricated elements are erected onto strip footings, raft-thickened edgeswhere and beams. Only after the insertion of furthe fur therr shims, shi ms, gro grouti uting ng the und unders erside ide of the elemen ele ment,t, or som somee settle set tlemen mentt wil willl the element weight redistribute from the initial shim supports.
) d e t n i r p n e h w d e e t n a r a u g t o n y c n e r r u c t n e m u c o D ( 6 1 0 2 b e F 4 2 n o D T L Y T P A I L A R T S U A E K R U O R O G N I A L y b d e s s e c c A
(b)
Provision of sufficient footing dimensions to accept the load and location of shims and accommodate the required reinforcement, considering the allowable construction tolerances.
(c)
The overall area of the shim to be selected, so that the bearing strength of the footing surface with which it is in contact is not exceeded.
(d)
The erection sequence of prefabricated elements that may produce a more adverse loading condition in a supporting member than the final in-service loads. C2.7.1(d)
An example of how the erection sequence of elements may produce adverse loading conditions in a supporting member is the connection between a single pile and its pile cap, positioned symmetrically beneath the joint of two adjacent elements. The pile cap may be subjected to a greater moment (resulting from fro m loa loadd ecce eccentr ntrici icity) ty) after aft er the ere erecti ction on of the fir first st elemen ele mentt tha thann aft after er ere erecti ction on of both elements. The caps on steel screw piles and timber piles could be particularly susceptible to this problem. (e)
Settlement of supports. C2.7.1(e)
This may be particularly critical for tall, narrow elements and columns where a small vertical settlement at the base may result in a significant horizontal deflection at the top of the element.
2.7.2 Footings for the temporary support of elements (deadman anchors)
Temporary brace footings shall be designed to ensure sufficient capacity to resist the bracing forces, including uplift forces by virtue of— (a)
the self-weight of the brace footing; and
(b)
a combination of the self-weight of the brace footing and the properties of the soil in which it is cast, provided that such soil properties have been tested and the design parame par ameter terss specif spe cified ied by a geo geotec techni hnical cal engine eng ineer, er, taking tak ing int into o accoun acc ountt weathe wea the r effect eff ectss and soil conditions (e.g. degree of compaction and disturbance during the footing installation).
Detailed drawings of any required temporary footings shall be included in the erection documentation and, as minimum, the set-out and size of the temporary brace footings shall be nominated. The specification of concrete for temporary brace footings shall nominate the following criteria: (i)
The strength required to develop the brace insert strength at the time of bracing.
(ii)
The requirements for in-service loading, if any, durability and any construction requirements such as workability.
Temporary brace footing inserts shall comply with Clause 2.5.4. © Standards
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C2.7.2
Where permanent structure is not available, not suitable or not chosen to resist the loads imposed by temporary support, it may be necessary to use a temporary footing (commonly known as the deadman footing) as a temporary support and anchor. These temporary footings should be designed for both vertical and horizontal loads. These may be designed as strip or pad footings or piers. The use of concrete mass blocks sitting on top of the ground, as anchorages for installing brace footings, should only be used if they have been designed for the intended purpose and applied loads. The requirement for the development of concrete strength at the time of bracing will commonly require the specification of early-age strength concrete. If tem tempor porary ary foo footin tings gs are cas castt usi using ng low str streng ength th con concre crete te (e.g. (e. g. 20 to 25 MPa at 28 d), care needs to be taken to ensure they reach the specified strength at the time of bracing. Where concrete piles or bored piers are used as temporary footings, they should be designed with cast-in reinforcement that runs the full length of the pile. Where expansion anchors are used, edge distances can be critical, and a diameter of the pile of not less than 600 mm should usually be used unless a pile cap is provided. The piles will need to be designed to resist uplift forces, down forces and lateral forces. Sandy, wet or poorly compacted soils may not be suitable for this type of anchoring. ) d e t n i r p n e h w d e e t n a r a u g t o n y c n e r r u c t n e m u c o D ( 6 1 0 2 b e F 4 2 n o D T L Y T P A I L A R T S U A E K R U O R O G N I A L
Without a verified geotechnical test and design report, the brace footings cannot be assumed to Where be capable resisting thegeotechnical uplift forcesadvice unlessonthey of sufficient self-weight. screw of piles are used, theirare capacity should be obtained. Such advice should consider deterioration of soil properties in wet conditions particularly with respect to pull-out. Trench footings of sufficient dimensions and weight often provide an economical solution for a line of braces. The footing of the permanent structure may be suitable for the temporary footings, subject to detailed design. For the des design ign of the tem tempor porary ary foo footin ting, g, two des design ign cas cases es wil willl nee needd to be con consid sidere eredd depending on the direction of the wind. In one case there will be uplift together with horizontal force in one direction on the temporary footing, and in the other case there will be a force down again with a horizontal force in the other direction on the temporary footing. Of the two different loading cases, the case where the wind tends to pul pull the tem tempor foo footin tingg out of the gro ground und is usu usuall allyy the mor moree critic cri tical al wit withh res respec pectt to the ldesign ofporary theary temporary footing. 2.8 CONNECTIONS 2.8.1 General
Connections shall allow for independent shrinkage and thermal movements between prefab pre fabric ricate ated d elemen ele ments ts and other oth er str struct uctura urall membe me mbers, rs, and allow all ow for the constr con struct uction ion tolerances in locating fixings and other cast-in components.
b y d e s s e c c A
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2.8.2 Horizontal restraint of vertical elements 2.8.2.1
Construction conditions
Horizontal restraint at the base of the element during construction shall be considered. C2.8.2.1
Dowels will not provide effective lateral restraint until they are grouted and cured. Designers should satisfy themselves that there is sufficient restraint to the dowel or the grout tubes at the base of panels to resist the temporary loads during erection and the in-service condition. Braces should not be removed until such time as the dowels have been grouted and cured, and it is safe to remove the braces. For brace removal, see Section 6. Consideration should be given to positive fixing of the base of the element where horizontal displacement when temporarily braced can cause significant vertical movement. Where the base of the element is elevated above ground level or when an element is braced at or below its centroid of area, there should be positive connections at the base of the element. 2.8.2.2 ) d e t n i r p n e h w d e e t n a r a u g t o n y c n e r r u c t n e m u c o D ( 6 1 0 2 b e F 4 2 n o D T L Y T P A I L A R T S U A E K R U O R O G N I A L b y d e s s e c c A
In-service conditions
A fixing system shall be used to resist the horizontal load transmitted from the element into the footings or floor slabs in the in-service condition. Friction forces shall not be relied upon to resist any part of this load. The fixings shall be capable of resisting the greater of— (a)
forces resulting from the design loadings;
(b)
an unfactored live load of 3 kN/m (or 5 kN min.) applied over the full element width, perpen per pendic dicula ularr to t o the t he plane pla ne of the elemen ele ment, t, at the level lev el of the connec con nectio tions; ns; or
(c)
5% of the value ( G + ψ Q) for the connection under consideration, c
where
G
= permanent action (self-weight or ‘dead’ action)
ψ c
= combination factor for imposed action
Q
= imposed action (due to occupancy and use, ‘live’ action)
NOTE: For mini mum lateral lat eral resi resista stance nce of cconnec onnection tion and tie ties, s, see AS/NZ S 1170.0 11 70.0:2002 :2002..
C2.8.2.2
Designers should be aware that pitched rafters can exert significant outward loads onto braced elements. In some cases, these forces are sufficient to cause failure of the brace inserts/bolts.
Lat erall outw Latera o utward ard forces for ces on elemen ele ments ts dur during ing the ere erecti ction on of pit pitche chedd rroof oof raf rafter terss can c an res result ult in the overloading of the temporary bracing and its connections. During the release of the rafter’s weight from the crane, the braces adjacent to the rafter being erected will need to be monitored and adjusted accordingly. Superimposed loads applicable to flooring elements could also include steelwork, formwo for mwork, rk, mob mobile ile pla plant, nt, sto storag ragee of bui buildi lding ng mat materi erials als and loa loads ds imp impose osedd by oth other er temporary bracing. Lat erall out Latera outwar wardd forces for ces are gen genera erated ted by the self-w sel f-weig eight ht of the elemen ele mentt and con constr struct uction ion materials being stacked upon the element. Care will need to be taken to avoid punching by ensuring that concentrated loads on voided flooring elements are adequately distributed. Any add additi itiona onall impo i mposed sed loa loads ds sho should uld be ref referr erred ed to the des design igner. er. © Standards
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AS 3850.2:2015 3850.2:2015
2.9 STRONGBACKS
Strongbacks may be required to reduce deflection, which could cause cracking and element failure. Strongbacks may also be required to control the movement of elements during lifting and ensure the stability of the element once erected. NOTE: For exam example pless of stro strongba ngbacks cks and their the ir appl applica ication tion , ssee ee Figure Figu re 2 .11.
Where braces and strongbacks are pre-attached on the same element, their locations shall allow the rigging to operate without interference, at all angles of element rotation.
) d e t n i r p n e h w d e e t n a r a u g t o n y c n e r r u c t n e m u c o D ( 6 1 0 2 b e F 4 2 n o D T L Y T P A I L A R T S U A E K R U O R O G N I A L
B l o c k f o r pa n e l t h i c k n e ss a n d h e i g h t o f o pe n i n g (a ) S t r o n g ba c k a ppl i c a t i o n s
Insert bolt with pla te a nd wa she r
Steel sections
Fix ing a s spe c ifie d by a n e ngine e r a nd insta lle d in a c c or da nc e with the ma nufa c tur e r ’s spe c ific a tion
( b) Str ongba c k—Ste e l
NOTES: 1
Where strongbacks with holes are used, holes used to attach a strongback to a panel/element should be clean so as to ensure a secure fit when it is attached.
2
Cast-in ferrules should be used in preference to expansion anchors for attaching strongbacks to precast elements.
3
Where bolts are used for ca cast-in st-in inserts, a suitable anti-loosening device (e.g. spring washer) may be used under the attaching bolt head when attaching strongbacks to precast elements.
b y d e s s e c c A
FIGURE 2.11 STRONGBACKS
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2.10 DOCUMENTATION 2.10.1 General
Drawings shall comply with AS/NZS 1100.501. The project documentation shall provide all information necessary to ensure the robustness and stability of the structure during construction, and that the completed structure complies with the intentions of the in-service design. Structural drawings shall include sufficient detail to allow at least one robust method of construction of the prefabricated concrete elements. NOTE: The drawings draw ings,, incl uding manu fact facture ure (sho (shop) p) draw drawings ings,, may be combine comb ined d or prov provided ided as separate sheets for layout plans, manufacture and erection.
2.10.2 Information required on drawings
Information required on drawings shall be in accordance with Appendix A. The structural drawings and manufacture (shop) drawings shall be available on site at the time of erection. 2.10.3 Review of manufacture (shop) drawings 2.10.3.1 ) d e t n i r p n e h w d e e t n a r a u g t o n y c n e r r u c t n e m u c o D ( 6 1 0 2 b e F 4 2 n o D T L Y T P A I L A R T S U A E K R U O R O G N I A L
Manufacture (shop) drawings
The manufacture (shop) drawings, including any layout plans and elevations, shall be submitted for certification and endorsement by the in-service designer and erection designer, prior to manufacture of the elements. 2.10.3.2
Erection documentation
The erection documentation shall be submitted for certification and endorsement by the erection designer, prior to the erection of any elements. C2.10
The concrete strength grade on the shop drawings may be higher than that specified on the structural drawings to achieve the concrete strength required at the time of lifting. When the structural drawings and manufacture (shop) detail drawings are being produc pro duced ed as one ent entity ity by one org organi anizat zation ion,, it is suffic suf ficien ientt for the inf inform ormati ation on spe specif cified ied in Clause 2.10.1 to be included in the complete set of drawings. In add additi ition, on, it is rec recomm ommend ended ed tha thatt the sho shopp dra drawi wings ngs inc includ ludee a lay layout out drawin dra wingg (marking plan) showing the following: (a) The location of each element. (b)
Where applicable, rigging diagrams detailing the required configurations with sling lengths, spreader/lifting beam requirements and arrangement of sheaves.
(c)
Specifications for the brace fixings and brace footings, including the required concrete strength of the footing at the time of erection.
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AS 3850.2:2015 3850.2:2015
2.11 TOLERANCES
Unless otherwise specified, the dimensional tolerances for as-cast elements, casting bed and insert locations shall be as follows: (a)
As cas castt elem e lement entss (includes permanent fixing insert locations) see Table 2.5.
(b)
Casting bed The tolerance on deviation from planeness of the casting bed, measured in any direction using a 3 m straightedge (as set out in AS 3610.1) shall be ±3 mm.
(c)
Temporary fixing inserts (for lifting, bracing, strongbacks, etc.) see Table 2.6. (d) Pre Pre-te -tensi nsione onedd eelem lement entss See Table 2.7 and Table 2.8. Where more stringent tolerances are required, they shall be specified in the appropriate design documentation and manufacture (shop) drawings. The effects of cumulative tolerances shall be considered. The total accumulation of tolerance shall be not be greater than 20 mm when related to set-out grids and data.
When stack casting, the top surface of the first element will need to be carefully levelled to ensure successive elements do not inherit level and profile deviations from the base element. This might be achieved by using a dumpy level.
C2.11
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TABLE 2.5 TOLERANCES ON AS-CAST ELEMENTS (NOT PRE-TENSIONED) Acceptable deviation, mm
Tolerance classification
Linear dimensions
Description
Dimensions of flat elements
Plus
Minus
