The calculation of temporary support for casting PSC Box Girder 45 M which has been implemented at BR 553 and BR 557 of Barang to Cuttak Section in Or...
SUPPORT FOR CASTING PSC 45.1 m GIRDER BRIDGE BR-553
A. LOADING CONDITION
Dead Load Shuttering & Accesories Manpower Total weight Effective Span of Steel Girder To be support by 5 Longitudinal Beam
= 657.0 = 76.5 = 5.0 = 738.5 = 45100
Load on each beam (DL+LL)
=
738.5 4 x 45.1
ton ton ton ton mm = 4.1t / m'
Wind Load Wind pressure is considered at 8 m height from HWL with the wind velocity is about 113 km/h (during monsoon season, thus the wind pressure is 82 kg/m2. 82 x3.4 x 45.1 = 1143.08.3kg The horizontal load on each cross portal = 11 Hydrostatic pressure of running water during monsoon season: Where: =Hydrostatic pressure of running water (ton) =Coefficient of pillar shape = 0.07 (square) =Velocity of running water during flood (m/sec) = 2.778 m/sec (equal to 10 km/hr-estimate) =Width of structure (m) = 0.6 m = Depth of water level during flood (m) = 10.3 m (as recorded at site) = 3.339ton (at 0.666x10.3 = 6.86m from the bed level)
Runner beam use ISMB 100 @ 625 mm ctc ( +/-72 numbers along the girder) 738.5 Load on each beam = =10.26t 72 10.26 Width of PSC girder is 3.0 m, hence the load on runner beam = = 3.42t / m' 3 Load for working platform = 0.25 x 0.625 = 0.16 t/m on each runner beam 3.42t/m2
The calculation result is as on follows: Mmax = 0.16 tm Vmax = 1.34 ton Beam Properties ISMB 100 A = 14.60 cm2 Ix = 257.5 cm4 Iy = 40.8 cm4 Wx = 51.5 cm3 Wy = 10.9 cm3 σ all = 2400/1.5 = 1600 kg/cm2
tw h1 h2
= 4.0 = 85.6 = 14.4
mm mm mm
STRESS CHECKING
a.
Stress Checking M max 0.16 x10 5 2 2 = = 310.68kg / cm < 1600kg / cm σ = 51.5 w x check for tensile stress h1 85.6 = = 21.4 < 85 , hence OK t w 4
b.
Shear Stress 2 Resisting area = 10 x 0.4 = 4 cm V max 1.34 x10 3 2 2 = = 335kg / cm < 1020 kg / cm (IRS Steel Bridge Code) τ = Ar 4
c.
Diagonal Buckling h l 8.56 2 = 1 6= 6 = 52.42 <910 kg/cm 0.4 r t w
d.
Web Crippling at Support Bearing length = 75 mm Induced bearing stress R 1340 2 = = 335.19 < 1890kg / cm = t w x( B + 3h2 ) 0.4 x(7.5 + 3 x1.44) (IRS Steel Bridge Code)
e.
Direct Compression in web P < 0.75 f y Bt B = b + 2 3h = 7.5 + 2 3 x1.44 = 12.5 1340 2 = 268 < 1600kg / cm 12.5 x0.4 The web is sufficient not required to be stiffened
Deflection 715 L i) = = 37.41 < 100 , hence OK 19.11 19.11 1430 L ii) = = 74.88 < 100 , hence OK 19.11 19.11
C. LONGITUDINAL BEAM
The calculation result is as follows: Mmax = 16.31 tm Vmax = 11.65 ton Beam Properties ISMB 400 A = 78.46 cm2 Ix = 20460 cm4 Iy = 422.1 cm4 Wx = 1023 cm3 Wy = 88.87 cm3 = 2400/1.5 = 1600 kg/cm2 σ all
tw h1 h2 tf
= 8.9 = 334.4 = 32.8 = 16
mm mm mm mm
STRESS CHECKING
g.
Stress Checking M max 16.31 x10 5 2 2 = = 1594.33kg / cm < 1600 kg / cm σ = w x 1023
h.
Shear Stress 2 Resisting area = 40 x 0.89 = 35.6 cm V max 11.65 x10 3 2 2 τ = = = 327kg / cm < 1020 kg / cm (IRS Steel Bridge Code) Ar 35.6
i.
Web Crippling at Support Bearing length = 210 mm Induced bearing stress R 11650 2 = = = 542.32 < 1890kg / cm t w x( B + 3h2 ) 0.89 x(21 + 3 x3.28) (IRS Steel Bridge Code)
j.
Direct Compression in web P < 0.75 f y Bt B = b + 2 3h = 14 + 2 3 x1.6 = 19.54
19.54 x0.89 The web is sufficient not required to be stiffened k.
Deflection f = 1.6cm <
l
325
=
560 325
= 1.723cm ok!
D. MAIN CROSS BEAM
The calculation result is as follows: Mmax = 8.09 tm Vmax = 13.04 ton Beam Properties ISMB 400 A = 78.46 cm2 Ix = 20460 cm4 Iy = 422.1 cm4 Wx = 1023 cm3 Wy = 88.87 cm3 σ all = 2400/1.5 = 1600 kg/cm2
tw h1 h2
= 8.9 = 334.4 = 32.8
mm mm mm
STRESS CHECKING
a.
Stress Checking M max 8.09 x10 5 2 2 σ = = = 790.81kg / cm < 1600 kg / cm w x 1023
b.
Shear Stress V max 13.04 x10 3 2 2 = = 366.3kg / cm < 1020kg / cm τ = Ar 35.6
c.
Web Crippling at Support Bearing Length = 300 mm Hence bearing stress R 13040 2 = = 442.16 < 1890kg / cm = t w x(a + 3h2 ) 0.89 x(30 + 3 x3.28) (IRS Steel Bridge Code)
Direct Compression in web P < 0.75 f y Bt B = b + 2 3h = 14 + 2 3 x1.6 = 19.54 13.04 x10 3
= 749.83 < 1600 kg / cm
2
19.54 x0.89 The web is sufficient not required to be stiffened
E. BRACING
The calculation result is as follows: Compression Force = 1447 kg (long bracing) Compression Force = 4698 kg (cross bracing) Bracing Properties L 50.50.5 A = 4.79 cm2 Ix = 11 cm4 Iy = 11 cm4 Wx = 3.1 cm3 Wy = 3.1 cm3
r = 1.52 cm
Compression Stress (long bracing)
Stress =
1447 4.79
= 302.1kg / cm
2
l
for this stress is 190 r Hence unsupported length = 190 x 1.52 x 2 =577.6 cm > 536 cm (actual length) Compression Stress (cross bracing)
Stress =
4698 4.79
= 980.8kg / cm
2
l
for this stress is 80 r Hence unsupported length = 80 x 1.52 x 2= 243 cm > 230 cm (actual length) for longitudinal and cross bracing using 2 L50.50.5
CC Crib made from 4 ISA 75.75.8 (600x600x1800mm) A = 11.38 cm2 W = 8.9 kg/m Exx/eyy = 5.36 cm cxx.cyy = 2.14 cm Ixx/Iyy = 59 cm4 Ivv = 24 cm4 Rxx/ryy = 2.28 cm Rvv = 1.45 cm Ixx of conposite section 2 = 4 (Ixx + AD ) 2 = 4 (59 + 11.38 x 29.2 ) = 39048.17 cm4 Rxz (composite) =
I xxcomp A
=
39048.17 4 x11.38
= 29.29cm
Maxm allowable load on crib = 51 ton (actual force is 36.7 ton-taken from cross calculation) Hence stress =
51000 4 x11.38
= 1120.39kg / cm
2
l
for this stress is 64.1 r Hence unsupported length = 64.1 x 29.29 = 1877.50 cm = 18.78 m Cribs are restrained with bracing longitudinally and laterally with not more than 2x1.8 m i.e 3.6 m. Check for buckling of crib 2
Rvv = 1.45 cm, stress = 1120.39 kg/cm l for this stress is 64.1 r Unrestrained length fro this stress is 64.1 x 1.45 = 92.945cm Actual unrestrained length of member of CC Crib is 60 cm and hence OK.
Soil Data C = 3 t/m2 0 φ = 6.5 = 1.888 t/m3 N c = 7.32 N q = 1.64 N γ = 0
Type of Foundation Type rectangle: L = 1.80 m B = 1.40 m D = 0.40 m Df = 1.50 m Ultimate Bearing Capacity . c + γ D . f . N q + 0,44.. B.γ . N γ q d = 1.16.c N q d = (1.234 x3 x7.32) + (1.888 x1.50 x1.64) + (0.42 x1.0 x1.888 x0)
= 31.743 t/m2 Safe bearing capacity =
31.743 2.0
= 15.87t / m 2 (being temporary structure)
Vertical Working Load Pressure
Total Load = 29.43 ton 29.43 P 2 = = 11.68t / m < 15.87t / m 2 ok q= A 1.4 x1.8 Horizontal Working Load :
Total Load = 2101 kg W = (0.5x1.8x2.6x1.888)+(0. (0.5x1.8x 2.6x1.888)+(0.5x1.8x0.4x1. 5x1.8x0.4x1.888)+(1.4x1.8x 888)+(1.4x1.8x2.4)= 2.4)= 11.14 tons wx 0.6 11140 x 0.6 Fs = = = 3.18 > 1.5 safe 2101 Ph
H. FOUNDATION (PILE FOUNDATION – CASTING PSC DURING MONSOON)
Pile data: Diameter : 40.0 cm thick 6mm Length : 16.5m Material : Steel Pipe Pile
1. Allowable Bearing Capacity of Pile Due to Soil Condition Ra = 1/3 (30 x N x AP + ( Σ Ns/5 x Ls + Σ N x Lc) x Ψ) Where: N : average N value between 1.0 d below pile and 4.0d above pile : (25+19)/2 = 22 AP : Pile end area = 0.126 m2 Ns : Average N value considered as skin friction of sandy soil : 16.27 Ls : Length of pile in sandy layer = 12.5 m Qu : Average unconfined compression strength considered as skin friction in cohesive soil = 0 Lc : Length of pile in cohesive layer = 0 m Ψ : Circumferential length of pile = 1.257 m
Ra
= 1/3 (30 x 22 x 0.126 + (16.27/5 x 12.5 + 0 x 0) x 1.257) = 44.76 ton
Number of piles required = 26.85/44.76 =0.6 nos ~ 1 nos
The maximum deflection at pile top is 0.5 cm <
Max bending moment 23.16 kNm = 2.316 tm
Stress Checking M max 2.316 x10 5 2 2 = = 293.7kg / cm < 1600 kg / cm σ = w x 788.6
I. FOUNDATION (PILE FOUNDATION – CASTING PSC DURING MONSOON)
Pile data: Diameter : 40.0 cm Length : 16.5m Material : Bored Pile
2. Allowable Bearing Capacity of Pile Due to Soil Condition Ra = 1/3 (30 x N x AP + ( Σ Ns/2 x Ls + Σ N/2 x Lc) x Ψ) Where: N : average N value between 1.0 d below pile and 4.0d above pile : (25+19)/2 = 22 AP : Pile end area = 0.126 m2 Ns : Average N value considered as skin friction of sandy soil : 16.27 Ls : Length of pile in sandy layer = 12.5 m Qu : Average unconfined compression strength considered as skin friction in cohesive soil = 0 Lc : Length of pile in cohesive layer = 0 m Ψ : Circumferential length of pile = 1.257 m
Ra
= 1/3 (30 x 22 x 0.126 + (16.27/2 x 12.5 + 0/2 x 0) x 1.257) = 70.32 ton
Number of piles required = 26.85/70.32 =0.38 nos ~ 1 nos
The maximum deflection at pile top is 1.2 cm <
Pile capacity 523kN (axial load) with 79kN-m (bending moment) > actual axial load 268.5kN with bending moment 50kN-m. Thus, Bored Pile dia 400mm with main rebar 6-D16 and spiral bar D-10
