DESIGN OF RCC T - GIRDER DECK USING MORICE & LITTLE METHOD...
Description
DESIGN OF RCC T - GIRDER DECK USING MORICE & LITTLE METHOD : (All blue coloured fonts depict inputs) BASIC DESIGN DATA 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28
Effective span Clear carriage way Spacing of main girder c/c Spacing of cross girder c/c Width of crash barier Thk of deck slab Thk of wearing coat Length of cantilever Cantilever slab thk at fixed end Cantilever slab thk at free end No of main girder Depth of main girder Web thk of main girder ( at center ) Web thk of main girder ( at support ) Length of extra widening ( varrying ) Length of extra widening ( uniform ) Top haunch Bottom haunch Bottom bulb No of cross girder Depth of cross girder Web thk of cross girder Grade of concrete Grade of reinforcement Clear cover Unit weight of concrete Weight of wearing course Weight of crash barrier
19.500 m 11.000 m 2.650 m 9.750 m 0.550 m 0.250 m 0.065 m 2.075 m 0.300 m 0.200 m 4 m 2.000 m 0.325 m 0.625 m 0.900 m 0.600 m 0.300 x 0.150 m 0.150 x 0.150 m 0.625 x 0.250 m 3 m 1.750 m 0.325 m 30 N/mm2 415 N/mm2 0.04 m 2.400 t/m3 0.200 t/m2 1.000 t/m
29
Stress in concrete (compression)
fc
1000
t/m2
30 31
Stress in steel (tension) Modular ratio
ft m
20000 10
t/m2
Calculation of distribution coefficients by Morrice - Little method : Effective span (2a) Total width (2b)
= =
19.500 12.100
m m
p Computation of longitudinal rigidity beff beff = = > beff =
y N
A
Distance of cg from top fibre (y)
lo/5 + bw [ Cl. 305.15.2 IRC 21 ] 4.225 m lo = 19.5 m 2.650 m [ c/c distance of 2.650 m longitudinal girder]
= = =
Moment of inertia of longitudinal girder (IL) Flextural rigidity per unit width ( Dx ) = (IL x E) /p Computation of transverse rigidity
0.666 0.602 0.227E
m m4
19.50 m For end cross girder Its behave like L - beam beff 0.25 N 1.5
A
0.325 Distance of cg from top fibre (y) Moment of inertia of end cross girder (IT1)
beff = lo/10 + bw [ Cl. 305.15.2 IRC 21 ] lo = 0.7*2.65 1.855 m beff = 0.511 m
= =
0.818 0.170
m m4
For intermediate cross girder Its behave like T - beam beff 0.25 A
N
beff = lo/5 + bw [ Cl. 305.15.2 IRC 21 ] lo = 3*2.65 ###### beff = 1.915 m
1.5 0.325 Distance of cg from top fibre (y)
= =
Moment of inertia of intermediate cross girder (IT2) For deck slab 16.889 0.25
N
Moment of inertia of deck slab (IT3) Flextural rigidity per unit length ( Dy ) = (SIT x E )/leff Torsional rigidity of rectangle (Ri) = G x K x b3 x d Modulus of rigidity (G) = E/2x(1+m) b = Shorter side d = longer side K corresponds to d/b from table. For longitudinal girder (Consider shaded portion only)
-b -3b/4 -b/2 -b/4 0 b/4 b/2 3b/4 b Slw SlwKa K' = SlwKa/Slw
2.65 G2
2.65
2.075 G4
G3
lwKa -b
-3b/4
-b/2
-b/4
0
b/4
b/2
3b/4
b
1.87 0.21 0.00 0.00 0.00 0.00 0.00 -0.05 -0.46
1.38 0.17 0.00 0.00 0.00 0.00 0.00 -0.02 -0.30
0.92 0.13 0.00 0.00 0.00 0.00 0.00 0.00 -0.14
0.58 0.09 0.00 0.00 0.00 0.00 0.00 0.03 0.06
0.26 0.05 0.00 0.00 0.00 0.00 0.00 0.05 0.26
0.06 0.03 0.00 0.00 0.00 0.00 0.00 0.09 0.58
-0.14 0.00 0.00 0.00 0.00 0.00 0.00 0.13 0.92
-0.30 -0.02 0.00 0.00 0.00 0.00 0.00 0.17 1.38
-0.46 -0.05 0.00 0.00 0.00 0.00 0.00 0.21 1.87
1.57 1.566
1.23 1.231
0.91 0.905
0.75 0.747
0.63 0.629
0.75 0.747
0.91 0.905
1.23 1.231
1.57 1.566
Distribution coefficient K' at girder location Girder Nr. G1 G2 G3 G4 K' 1.221 0.806 0.774 1.221 Note : Coefficients have been increased by 10% to take into account the effect of higher harmonics.
Distribution coefficient K' for live load (3 lane class A) -b
-3b/4
-b/2
-b/4
Class A
b/4
Class A
1.8m
0.95m
0
1.7m
2.075 G1
b
3b/4
Class A
1.8m
2.65
b/2
1.7m
2.65 G2
1.8m
2.65
2.075 G4
G3
lwKa Ref. Pt Load at -b -3b/4 -b/2 -b/4 0 b/4 b/2 3b/4 b Slw
Distribution coefficient K' at girder location Girder Nr. G1 G2 G3 G4 K' 1.289 1.207 1.087 0.860 Note : Coefficients have been increased by 10% to take into account the effect of higher harmonics.
Distribution coefficient K' for live load (70 - R) -b
-b -3b/4 -b/2 -b/4 0 b/4 b/2 3b/4 b Slw SlwKa K' = SlwKa/Slw
-b
-3b/4
-b/2
-b/4
0
b/4
b/2
3b/4
b
0.00 15.06 13.05 8.12 0.00 0.00 0.00 0.00 0.00
0.00 12.33 11.92 8.19 0.00 0.00 0.00 0.00 0.00
0.00 9.20 10.49 8.44 0.00 0.00 0.00 0.00 0.00
0.00 6.38 8.33 8.27 0.00 0.00 0.00 0.00 0.00
0.00 3.86 6.16 7.23 0.00 0.00 0.00 0.00 0.00
0.00 1.84 4.15 5.86 0.00 0.00 0.00 0.00 0.00
0.00 -0.07 1.96 4.11 0.00 0.00 0.00 0.00 0.00
0.00 -1.56 -0.09 2.36 0.00 0.00 0.00 0.00 0.00
0.00 -3.23 -2.01 0.78 0.00 0.00 0.00 0.00 0.00
36.23 2.131
32.44 1.908
28.14 1.655
22.97 1.351
17.25 1.015
11.85 0.697
6.01 0.353
0.70 0.041
-4.47 -0.263
Distribution coefficient K' at girder location Girder Nr. G1 G2 G3 G4 K' 1.995 1.440 0.897 0.173 Note : Coefficients have been increased by 10% to take into account the effect of higher harmonics.
Distribution coefficient K' for live load (1lane class A + 70 - R) -b
-b -3b/4 -b/2 -b/4 0 b/4 b/2 3b/4 b Slw SlwKa K' = SlwKa/Slw
-b
-3b/4
-b/2
-b/4
0
b/4
b/2
3b/4
b
0.00 15.07 13.04 8.43 3.29 0.62 -0.28 0.00 0.00
0.00 12.33 11.91 8.50 4.44 1.87 -0.01 0.00 0.00
0.00 9.20 10.49 8.76 5.48 3.27 0.27 0.00 0.00
0.00 6.38 8.32 8.58 6.49 4.65 0.58 0.00 0.00
0.00 3.86 6.16 7.51 7.04 5.74 0.86 0.00 0.00
0.00 1.84 4.15 6.08 6.49 6.56 1.16 0.00 0.00
0.00 -0.07 1.96 4.27 5.48 6.70 1.47 0.00 0.00
0.00 -1.56 -0.09 2.45 4.44 6.50 1.67 0.00 0.00
0.00 -3.24 -2.01 0.80 3.29 6.45 1.82 0.00 0.00
40.16 1.414
39.05 1.375
37.47 1.319
35.00 1.233
31.17 1.097
26.28 0.926
19.80 0.697
13.40 0.472
7.12 0.251
Distribution coefficient K' at girder location Girder Nr. G1 G2 G3 G4 K' 1.490 1.337 1.088 0.611 Note : Coefficients have been increased by 10% to take into account the effect of higher harmonics.
DESIGN OF MAIN GIRDER Calculation of dead load
Inner girder 1 2 3 4 5
Weight of web Weight of top haunch Weight of bottom haunch Weight of bulb Weight of deck slab
=(0.5*(2*2-2*0.25 -2*0.25-0.15= 0.98 t/m 0.15)*(0.625-0.325) + (0.5*(2*2-2*0.3-2*0.25Wt due to extra widening (vary) = 0.98 to 0 t/m 0.15)*(0.625-0.325))*0.5*2.4 Wt due to extra widening (uni)
Calculation of SIDL (uniform)
Inner girder 1
Weight of wearing coat
=
0.53
t/m
Weight of wearing coat
=
0.57
t/m
Calculation of SIDL (concentrated) 2 Weight of crash barrier Total concentrated SIDL
= =
2.00 2.00
t/m t/m
Outer girder 1
Calculation of bending moment and shear force (DL+SIDL) (Uniform SIDL like wearing coat)
Inner girder 2.67 t
2.67 t
2.67 t
9.75
9.75 3.83t/m
0.97t/m 0.9
0.6
19.5 m A
B
Support reaction at A
Sl. Nr.
Item
=
Deff from sup
Location Span Span (L/8) (L/4)
Span (L/2)
1
BM (t-m)
70.2
83.4
143.5
195.5
2
SF (t)
31.0
29.3
20.0
0.0
42.34
t
Outer girder 1.33 t
1.33 t 9.75
1.33 t 9.75
4.22t/m
0.98t/m 0.9
0.6
19.5 m A
B
Support reaction at A
Sl. Nr.
Item
=
Deff from sup
Location Span Span (L/8) (L/4)
Span (L/2)
1
BM (t-m)
75.7
89.9
154.2
207.6
2
SF (t)
33.4
31.5
21.2
0.0
44.17
t
Calculation of total BM and SF due to concentrated SIDL (Concentrated SIDL like kerb,crash barrier) 2.00t/m
19.5 m A
B
Support reaction at A
Sl. Nr.
Item
Deff from sup
Location Span Span (L/8) (L/4)
Span (L/2)
1
BM (t-m)
35.0
41.6
71.3
95.1
2
SF (t)
15.5
14.6
9.8
0.0
=
19.50
t
=
9
mm
=
6
mm
Calculation of short term deflection due to dead load & sidl D2 L/4 D1 =
D1 L/4
D2 L/4
L/4
=(5*19.5/16)*(2*(2*(195.5+207.6)+95.1)*0.5*19.5/3 )/ (31220.186*100*2*(0.296+0.338))*1000 =D1/(2)0.5 (considering parabolic profile) D2 = Calculation of bending moment and shear force (Live load)
The live load bending moment and shear force at various sections has been worked out using an inhouse fortran programme, which runs the train of wheels both in forward and reverse directions and gives the max moment with corresponding shear and max shear with corresponding moment. The results are presented in the following sheets.
Summary of bending moment SL. Section Girder Nr. considered location
1
2
3
4
At Deff from support At 1/8th span (L/8) At quarter span (L/4) At middle span (L/2)
Design live load B M ( t-m) BM (t-m) Total BM Total BM Total BM Total BM BM (t-m) (dl+uni for 1L Cl A for 1L Cl A for 70 - R for 70 - R 3 Lane 70 - R 1L Cl A (con sidl) sidl) (Reverse) (Forward) (Reverse) (Forward) Class A (wheel) + 70 - R
Inner
70.2
7.1
56.6
44.7
110.1
118.8
54.4
50.5
59.2
59.2
136.5
Outer
75.7
10.7
56.6
44.7
110.1
118.8
58.1
70.0
65.9
70.0
156.4
Inner
83.4
8.4
70.9
55.8
138.3
149.2
68.2
63.4
74.3
74.3
166.1
Outer
89.9
12.7
70.9
55.8
138.3
149.2
72.8
87.8
82.8
87.8
190.5
Inner
143.5
14.4
116.0
97.1
237.3
248.5
111.5
105.6
125.4
125.4
283.3
Outer
154.2
21.8
116.0
97.1
237.3
248.5
119.1
146.3
139.7
146.3
322.3
Inner
195.5
19.2
144.1
144.1
325.3
325.3
138.5
138.2
166.7
166.7
381.3
Outer
207.6
29.0
144.1
144.1
325.3
325.3
148.0
191.5
185.7
191.5
428.1
Average BM = Total BM/no of main girders Design concentrated SIDL BM = Average BM x DF(K') Design live load BM = Average BM x IF x DF(K') Reduced the BM by 10% for each additional loaded traffic lane in excess of 2 lanes. [ Cl.208.2 IRC 6, 1966]
Calculation of impact factor for live load. 1 2
Max Design design BM (t-m) LL BM
For class A = 1+ 4.5/(6+L) For 70 R (Wheeled)
1.18 1.18
From curve IRC 6 1966 Cl. 211.3
Design of section for flexure Inner girder SECTION
Outer girder Deff from support
DATA M (t.m) 136.5 h (m) 2.000 bf (m) 2.650 df (m) 0.250 bw (m) 0.325 Ast (m^2) 0.00482 c (m) 0.115 Asc (m^2) 0.00080 dc (m) 0.064 m 10.0 RESULTS d (m) 1.885 Asf (m^2) 0.00515 AA (m^2) 0.0000 A (m) 2.6500 B (m^2) 0.1110 C (m^3) -0.1828 n (m) 0.243 CC (m^2) 0.0332 jd (m) 1.804 fc (t/m^2) 231 fs (t/m^2) -15677
DESIGN OF CROSS GIRDER End cross girder The end cross girder is designed as a contineous deep beam for bearing replacement condition, contineous over knife supports at the jack locations. The CL of jacks are taken to be 650 mm from the CL of main girder. The reaction of main girder due to (DL+SIDL) are applied as load at the girder location as shown below. 50.12 t
46.26 t
46.11 t
2.650
0.65
1.35
A DF FEM Balance CO Balance CO Balance Total M
1.00 32.58 0.00 -32.58
32.58 -32.58
B 0.49 0.00 3.68 -16.29 8.92 0.00 0.47 -3.22
2.650
0.65
0.51 -7.52 3.83 -1.92 9.29 -0.96 0.49 3.22
0.65 C 0.51 7.52 -3.83 1.92 -1.91 4.64 -2.84 5.49
1.35
0.49 0.00 -3.68 1.84 -1.84 0.92 -2.73 -5.49
D 0.49 0.00 3.67 -1.84 1.84 -0.92 2.72 5.47
2.650
0.65
0.51 -7.49 3.82 -1.91 1.91 -4.64 2.84 -5.47
Max support moment (DL+SIDL) Max span moment (DL+SIDL) Designed of deep beam For span AB Lever arm Z = For span CD Lever arm Z =
50.12 t
0.65 E 0.51 7.49 -3.82 1.91 -9.28 0.96 -0.49 -3.23
1.350
0.49 0.00 -3.67 16.29 -8.92 0.00 -0.47 3.23
F 1.00 0.00 -32.58 32.58
32.58 -32.58
= 32.58 t-m = 10.68 t-m
[ As per clause 28.2, IS 456-1978 ]
L= 2.65 L/D = 1.514 0.2*(2.65+1.5*1.75)
D = 1.75 >= 1 for contineous beam
L= 2.65 L/D = 1.514 0.2*(2.65+1.5*1.75)
D = 1.75 >= 1 for contineous beam
0.65
= 1.055 m
= 1.055 m
Required Ast for max span M
=M/sst*Z
=10.682/1.055*20000
2 = 5.06 cm
=
Provided Ast
= 12.3 cm2
Required Ast for max support M =M/sst*Z =32.579/1.055*20000 Provide 3 nos 20 f + 2 nos 16 f + 2 nos 12 f Distributed as per clause 28.3.2 (b) IS 456-1978
11
2
Minimum Ast at bottom =0.2%bd =0.002*32.5*175 Provide 3 nos 16 f + 2 nos 16 f + 2 nos 12 f at bottom within a depth of (0.25D - 0.05L) from bottom face with a development length of (0.8*35*dia of bar)
cm
= 0.305 m = 448 mm
2 = 15.44 cm
= 15.7 cm2
Provided Ast Hanging reinforcement
[ As per clause 28.3.3, IS 456-1978 ]
Total shear
=50.121+46.107+46.264+50.121
= 192.6 t
Required Ast as hanging R/F
=192.6*10000/20000
= 96.3 cm2
Required Ast per m length Provide 2L 12 f
=96.3/7.95 @ 180 c/c as vertical reinforcement
= 12.1 cm2/m = 12.6 cm2/m
Provided Ast Side face reinforcement
[As per clause 31.4 IS-456, 1978]
0.1 % of web area on either face with spacing not more then 450 mm. Required Ast
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