Steel Truss Bridge Design Example

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1.0 Introduction

This design note consists of 40m through trussed bridge.

1. IRC:6-2000 2. IRC:21-2000 3. IRC:22-1986 4. IRC:24-2001 5. IS:11384-1985 6. BS:5400-Part5:1979

The analysis of the structure has been done by a complete mathematical modelling using STAAD-Pro analysis software, while the design is done manually in line with the procedure & parameters laid down in the following standards:

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2.0 Basic Design Data:

Statical scheme :

Main Girders : _{Simply supported N type trusses (2 sets)}

with concrete deck at the top acting compositely with the main longitudinals Cross Bracings : _{at locations of the joint of verticals & the top}

& bottom chord

Top chord bracings : _{No bracing as the composite deck will serve}

the purpose

Bottom chord bracing : _{At every panel, as crossed braces.}

Span of Main girders : 40 m

(c/c of bearing)

Carriageway width : 4.25 m

Crash barrier width : 0.45 m

Total clear width of structure : 5.15 m

(span of cross girders)

Wearing coarse thickness : 75 mm to be provided

100 mm for design purpose

Cross fall on roadway : 2.5 % in both directions

Minimum depth of slab : 200 mm

Live load : 24 R

Density of concrete : 2.5

Density of wearing coarse : 2.3

Density of steel : 7.85

Grade of Concrete : M 20

Grade of Steel : Fe 540

Yeild Stress of Steel : 390 MPa

Modulus of Elasticity of Steel : 2.11E+05 MPa

Modulus of Elasticity of Conc. : 27500.00 MPa

(as per IRC:21-2000 cl.303.1) Coefficient of thermal expansion

Steel : 0.000012 /°C

Concrete : 0.000012 /°C

(as per IRC:22) For class 25t tracked vehicle, impact factor

(as per IRC:6-2000 cl.211.2 & figure 5) 1.154 t/m3 t/m3 t/m3

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This design note consists of 40m through trussed bridge.

The analysis of the structure has been done by a complete mathematical modelling using STAAD-Pro analysis software, while the design is done manually in line with the procedure & parameters laid

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Design of Through Steel Bridge

Effective Span 40.0m

Calculation of Member properties Steel Members: B o tt o m c h o rd .( N D -1 ) 250 0.0101 0.1375 2 7 5 10 2 5 5 0.125 1 0 0.0001154585 0.000099524 0.0001601964 230 B o tt o m c h o rd .( N D -2 ) 250 0.0101 0.1375 2 7 5 10 2 5 5 0.125 1 0 0.0001154585 0.000099524 0.0001601964 230 B o tt o m c h o rd .( N D -3 ) 250 0.0101 0.1375 2 7 5 10 2 5 5 0.125 1 0 0.0001154585 0.000099524 0.0001601964 230 To p c h o rd .N D -1 250 0.0101 0.1375 2 7 5 10 2 5 5 0.125 1 0 0.0001154585 0.000099524 FX 0.0001601964 230

Cross sectional area (A) (m2₎:

C.g. distance from top (m): C.g. distance from left (m): Ix-x (I about x-axis) (m4):

Iy-y (I about y-axis) (m4):

I_x-y (torsional constant) (m4_):

Cross sectional area (A) (m2₎_:

Ix-y (torsional constant) (m4):

Cross sectional area (A) (m2₎_:

I_y-y (I about y-axis) (m4₎:

C.g. distance from top (m): C.g. distance from left (m): I_x-x (I about x-axis) (m4₎:

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To p c h o rd .N D -2 250 0.0101 0.1375 2 7 5 10 2 5 5 0.125 1 0 0.0001154585 0.000099524 0.0001601964 230 To p c h o rd .N D -3 250 0.0101 0.1375 2 7 5 10 2 5 5 0.125 1 0 0.0001154585 0.000099524 0.0001601964 230 V er ti ca l M em b er . 100 8 0.0035 C.g. distance from bottom (m) 0.1250 C.g. distance from left (m) 0.0500 8 23 4 0.00003198 0.00000134 0.00000007 0.0003 0.0003 8 0.0000 100 0.0000 D ia g o n a l M e m b e r. 250 0.0077 0.125 2 5 0 8 2 3 4 0.125 8 0.00007567 0.00007567 0.0001133799 234

Cross Sectional Area (m2₎

I_X-X (m4₎ I_Y-Y (m4₎ Torsional Constant (m4₎ Z_t (m3₎ Z_b (m3₎ Z_Left (m3₎ Z_Right (m3₎

C.g. distance from top (m): C.g. distance from left (m): I_x-x (I about x-axis) (m4₎:

y

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B o tt o m T ra n sv er se c h o rd .( IS M B 5 00 ) 150 17.4 _0.0096

C.g. distance from bottom (m) 0.2500 C.g. distance from left (m) 0.0750 9.4 46 5. 2 0.0003829 0.0000098 0.00000058 0.0015 0.0015 17.4 0.0001 150 0.0001 To p & B o tt o m B ra c in g M e m b e r. _0.0001136 0.00000 0.03780 0.00000026 0.00000256 0.00010 0.00000 2-ISA50x50x6 0.00001 Face to face 0.00000 with 20 mm gap in between To p M ai n T ra n sv er se M em b er . 150 8 0.0043 C.g. distance from bottom (m) 0.1250 C.g. distance from left (m) 0.0750 8 23 4 0.0000437 0.0000045 0.00000008 0.0003 0.0003 8 0.0001 150 0.0001

I_X-X (m4₎ I_Y-Y (m4₎ Torsional Constant (m4₎ Z_t (m3₎ Z_b (m3₎ Z_Left (m3₎ Z_Right (m3₎

(2-22 hole on each leg) C.g. distance from top (m): I_x-x (I about x-axis) (m4₎:

Ix-y (tortional constant) (m4):

z_t (m3_):

z_b (m3_):

I_X-X (m4₎ I_Y-Y (m4₎ Torsional Constant (m4₎ Z_t (m3₎ Z_b (m3₎ Z_Left (m3₎ Z_Right (m3₎ y y x x Y Y X X y y x x

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Design Of Bottom Transverse Member

0.925 m 10.87 dead load

6.412 kn 6.412 kn 4.313 SIDL

6 m DEAD LOAD ANALYSIS

1 Load calculation.

I) Due to deck slab= =0.23182*2.5*1.875*10 10.8665625 kn/m

ii) Due to kerb & railing = =2.461*1.875+0.454*1.875 5.465625 kn

iii) Due to future overlay= =0.1*1.875*2.3*10 4.3125 kn/m

iv) Using ISMB550 as member= 1.037 kn/m

2 Moment calculation

I) Moment due to dead load= =10.866563*6*6/8 48.8995313 knm

ii) Moment due to Railing & Kerb= =5.465*(6/2-0.925) 11.3411719 knm

iii) Moment due to overlay butemen= =4.3125*6*6/8 19.40625 knm

iv) Moment due to ISMB550 =1.037*6*6/8 4.6665 knm

LIVE LOAD ANALYSIS

64.04 kn 64.04 kn

520 1560

A B

6 m

Reaction at A=Ra= =64.04(2.98+5.06)/6 85.8136 KNM

Moment at mid span= 263.785883 knm

Load combination

1 Dead load + Deck Load= 53.5660313 knm

2 SIDL+LL= 294.533305 knm

Only steel member

Z required= 357106.875 mm3

357.106875 Using ISMB 550

Zxx= 2359.8

Check for only steel member

Calculated bending compression stress= 22.70 Mpa Hence ok

Calculated bending tension stress= 22.70 Mpa Hence ok

Check for composite section

Stress at level1 5.4889317 Mpa Hence ok

Stress at level4 -96.334557 Mpa Hence ok

cm3

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3.0 Calculation of section properties

Modular ratio(m): 10

Creep Factor(Kc): 0.5

20 10 Sectional Properties of Top Chord:

Member Profile:

2

0

Basic Property of ISMC 225: ₀

(refer IS:808-1989) 180

Sectional Area (A): 25.9

2694.6 187.2 0

2.3 cm

12.4 mm 6.4 mm For Steel Only Case:

Area of Top Chord:

(25.9*2*100-2*12.4*22-2*2*6.4*22)/10^6 =

C.g. Distance from top:

2*(2694.6*1e+04)/1e+012 =

2*(187.2*10000+25.9*100*(2.3*10+80)^2)/1e+012 = For Composite (short term loading) Case:

Area of Top Chord: 0.0041+(2575/10*200)/10^6 =

C.g. Distance from top:

(0.0041*(0.2+0.1)+(2575*200/10*200/2)/1e+09)/0.0555712 = Moduar ratio for permanent loadings(m_p):

Moduar ratio for transient loadings(m_t):

cm2

I_XX : _cm4 I

YY : cm4

C_YY :

Thickness of Flange (Av.), t_f = Thickness of Web, t_w =

(Assuming 2-22 hole on the web & 1-22 hole on top flanges of the channels)

I_x-x (I about x-axis) (m4₎:

m = m_t X

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0.000059+((200*2575^3/12)/10)/1e+012 = For Composite (long term loading) Case: Area of Top Chord:

0.00407+(2575*200+(6+0)/2*1)/(20*10^6) = C.g. Distance from top:

(0.0041*(0.2+0.1)+(200*2575*100)/20/1e+09)/0.0298 =

0.000059+((200*2575^3/12)/20)/1e+012 =

The other properties are calculated in line to above calculation & are tabulated as below:

Profile Item Value Steel only To p C h o rd 2575 0.00407 2 0 0 0.100 1 0.000054 0 ₀ 0.000059 0.0001 6 0.0005 0.0002 2-ISMC225 Back to back with 160 mm gap in between I_x-x (I about x-axis) (m4₎: 0.000054+0.0040712*(0.2+0.1-0.115)^2+ (2575*200^3/12+(2575*200*(200/2-0.115*1000)^2))/10/1e+012 =

m = m_p

0.00005+0.0041*(0.2+0.1-0.12744)^2+((2575*200^3/12+2575*200*(127.44-200/2)^2)/20)/1e+012 =

Memb er

Cross cestional area (A) (m2₎:

(2-22 hole on web, 1-22 hole on flange) C.g. distance from top (m):

I_x-y (tortional constant) (m4₎:

z_t (m3_): z_b (m3_): Y Y X X

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Profile Item Value Steel only Memb er B o tt o m C h o rd 0.00407 0.100 0.000054 0.000059 0.0001 0 ₀ 0.0005 0.0005 2-ISMC225 Back to back with 160 mm gap in between V e rt ic a ls 0.00511 0.100 0.000036 0.000022 0.0001 0.0004 0.0004 2-ISMC200 Face to face with 160 mm

edge to edge dist.

z_t (m3_):

z_b (m3_):

(2-22 hole on web) C.g. distance from top (m): I_x-x (I about x-axis) (m4₎:

z_t (m3_): z_b (m3_): Y Y X X Y Y X X

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Profile Item Value Steel only Memb er D ia g o n a ls 0.00511 0.100 0.000036 0.000022 0.0001 2-ISMC150 0.0004 Face to face 0.0004 with 160 mm

edge to edge dist.

B o tt o m B ra c in g 0.00057 0.004 0.0000001 0.0000001 0.0001 0.000036 0.000003 ISMA 50x50x6

z_t (m3_):

z_b (m3_):

z_t (m3_): z_b (m3_): Y Y X X Y Y X X

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Profile Item Value Steel only Memb er Tr a n s v e rs a ls a t c ro s s b ra c in g l o c a ti o n 0.00370 0.075 0.000016 0.000006 0.0001 0.0002 0.0002 2-ISMC150 Back to back with 20 mm gap in between 0.00169 0.075 0.000007 0.000001 0.0001 0.0001 0.0001 ISMB150

z_t (m3_): z_b (m3_): Tr a n s v e rs a ls a t lo c a ti o n s o th e r th a n X -b ra c in g s

z_t (m3_): z_b (m3_): Y Y X X Y Y X X

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Profile Item Value Steel only Memb er Tr a n s v e rs D ia g o n a ls 0.00140 0.075 0.000008 0.000001 0.0001 0.0001 0.0001 ISMC150

z_t (m3_):

z_b (m3_):

*

m_t = Properties of composite section using modular ratio as m_t # m_p = Properties of composite section using modular ratio as m_p

Y

X X

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Calculation of section properties

2575 180 ₀ 0 2-ISMC225 Back to back 0.0041 0.1 m 0.000054 0.000059 0.0556 0.115 m m2 m4 m4 m2 Y Y X

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0.000376 0.028515 0.0298 0.127 m 0.000282 0.014287 The other properties are calculated in line to above calculation & are tabulated as below:

Value 0.05557 0.02982 0.115 0.127 0.000376 0.000280 0.028515 0.014287 0.0001 0.0001 0.0033 0.0022 0.0008 0.0010 m4 m4 m2 m4 m4 m_t

*

m_p #

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Value

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Value

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Value

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Value

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Calculation of Member properties

Composite Members

Grade of Concrete = M20

E of Concrete = 25491.17

E of Steel = 211000

Modular Ratio for Short term loading = 8.28

Modular Ratio for Long term loading = 16.55

Member Profile Sectional Properties_8.28

Tr a n sv e rs e G ir d e rs ( IS M B 5 5 0 )

1875 (all in Steel units, except where specified otherwise)

190

2

0

0 _0.0734

0.0131

C.g. distance from bottom (m) 0.5179

C.g. distance from left (m) 0.9375

0.0016 8 0.0177 11.2 5 1 5 .6 1 9 .3 0.00001 0.0537 0.2961 0.0358 190 0.0031 19.3 0.1562 0.0189 0.1862 0.1862 Tr a n sv e rs e G ir d e rs ( Ty p e 2 ) 70 937.5 0.0455 190 2 0

0 _{C.g. distance from bottom (m)} _0.4858

C.g. distance from left (m) 0.3788

0.0015 0.0045 8 0.00001 5 1 5 .6 ₁9.3 11.2 0.0437 0.1580 0.0191 0.0030 190 19.3 0.0595 0.0072 0.0211 0.0211 0.0112 0.0112 0.0119 0.0987 N/mm2 N/mm2 Short Term  = Cross Sectional Area (m2₎

Area steel only(m2₎

I_X-X (m4₎ IY-Y (m

4₎

Torsional Constant (m4₎ Z1 (m

3_{) (in concrete units)} Z2 (m

3_{) (in concrete units)} Z3 (m3)

Z4 (m 3₎

ZA (m

3_{) (in concrete units)} ZA (m3)

ZB (m 3₎ ZC (m3)

I_X-X (m4₎ IY-Y (m4)

Torsional Constant (m4₎ Z1 (m3) (in concrete units) Z2 (m

Z4 (m 3₎

ZA1 (m

3_{) (in concrete units)} ZA3 (m3) ZB (m 3₎ Z_C (m3₎ ZD (m 3₎ ZE (m 3₎ ZF3 (m3) ZF1 (m

3_{) (in concrete units)} y y x x Level 1 Level 2 & Level 3 Level 4 A B C y y x x Level 1 Level 2 & Level 3

Level 4 A B C D E F

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16.55 0.0508 0.0131 C.g. distance from bottom (m) 0.3389 C.g. distance from left (m) 0.9375 0.0015 0.0111 0.000002 0.0585 0.1108 0.0067 0.0044 0.1952 0.0118 0.1163 0.1163 0.0333 C.g. distance from bottom (m) 0.4513 C.g. distance from left (m) 0.3332 0.0013 0.0032 0.000002 0.0697 0.1955 0.0118 0.0029 0.0793 0.0048 0.0192 0.0192 0.0090 0.0090 0.0097 0.1605 Long Term  =

Cross Sectional Area (m2₎ Area steel only(m2₎

I_X-X (m4₎ IY-Y (m

4₎

Torsional Constant (m4₎ Z1 (m

3_{) (in concrete units)} Z2 (m

Z4 (m 3₎

ZA (m

3_{) (in concrete units)} ZA (m3)

ZB (m 3₎ ZC (m3)

I_X-X (m4₎ IY-Y (m4)

Torsional Constant (m4₎ Z1 (m3) (in concrete units) Z2 (m

Z4 (m 3₎

ZA1 (m

3_{) (in concrete units)} ZA3 (m3) ZB (m 3₎ Z_C (m3₎ ZD (m 3₎ ZE (m 3₎ ZF3 (m3) ZF1 (m

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3.0 Calculation of section properties

Modular ratio(m): 10 Creep Factor(Kc): 0.5 20 10 Profile Item Value Steel only To p C h o rd 2575 0.00858 2 0 0 0.059 1 0.000048 0.000038 0.0001 1/2-ISMB500 0.0008 Top Fl. Width = 180 mm 0.0002 Top Fl. thickness = 17 mm Web Thickness = 10.2 mm with 260 x 20 thk plate on top B o tt o m C h o rd 0.00893 0.248 0.000081 0.000028 0.0001 1/2-ISMB600 Top Fl. Width = 210 mm 0.0003 Top Fl. thickness = 21 mm 0.0012 Web Thickness = 12.0 mm with 210 x 16 thk plate on bottom

Moduar ratio for permanent loadings(m_p): Moduar ratio for transient loadings(m_t):

Memb er

z_t (m3_):

z_b (m3_):

z_t (m3_): z_b (m3_): Y Y Y X X Y X X

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Profile Item Value Steel only Memb er V e rt ic a ls 0.00395 0.100 0.000022 0.000022 0.0001 0.0002 0.0002 200NB (Heavy) Tube D ia g o n a ls 0.00434 0.038 0.000011 0.000022 0.0001 2-ISA130x130x15 0.0003 Face to face 0.0001 with 20 mm gap in between

(2-22 hole on web) C.g. distance from top (m):

z_t (m3_):

z_b (m3_):

(2-22 hole on each leg) C.g. distance from top (m):

z_t (m3_): z_b (m3_): Y Y X X Y Y X X

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Profile Item Value Steel only Memb er B o tt o m B ra c in g 0.00044 0.004 1.29E-07 1.29E-07 0.0001 0.000036 0.000003 ISMA 50x50x6 Tr a n s v e rs a ls a t c ro s s b ra c in g l o c a ti o n _0.00101 0.033 0.000001 0.000001 0.0001 2.00E-05 2.00E-05 65NB (Heavy) Tube

z_t (m3_):

z_b (m3_):

C.g. distance from top (m):

z_t (m3_): z_b (m3_): Y Y X X Y Y X X

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Profile Item Value Steel only Memb er 0.00101 0.033 0.000001 0.000001 0.0001 2.00E-05 2.00E-05 65NB (Heavy) Tube Tr a n s v e rs D ia g o n a ls 0.00136 0.003 0.0000015 0.0000015 0.0001 0.000526 0.000015 ISA 100x100x8 Tr a n s v e rs a ls a t lo c a ti o n s o th e r th a n X -b ra c in g s

z_t (m3_):

z_b (m3_):

z_t (m3_):

z_b (m3_):

*

m_t = Properties of composite section using modular ratio as m_t # m_p = Properties of composite section using modular ratio as m_p

Y Y X X Y Y X X

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Calculation of section properties

Value 0.06008 0.03433 0.123 0.140 0.000405 0.000296 0.028494 0.014266 0.0001 0.0001 0.0033 0.0021 0.0012 0.0009 m_t

*

m_p #

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Value

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Value

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Value

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Page 31 of 63

4.0 Load Calculation

4.1 Selfweight of truss

4.2 Dead Load due to deck

The deck is proposed to be cast after erection of the trusses and all bracings in place. The weight of the deck concrete thus will be carried by the two truss only.

Running thickness of the deck: 200 mm

Additional thickness at the center for cross slope at deck: 53.125 mm

Integral Wearing Coarse : 12 mm

So, average (weighted) thickness of deck: 231.82 mm

So, Weight of the deck on the truss in running portion:

231.82*/2000**10 = 14.92 kN/m

load on each transverse girder due to deck slab= =2.5*231.82*2.5*10/1000

14.49 kN/m

4.3 Superimposed Dead Load a. Due to kerb 425 2 2 5 0.5*(0.45+0.425)*0.225**10 = 2.461 kN/m 450 b. Due to Railing 1. 1200 LONG ISMC 150 @ 1000c/c 1.2*16.4*10/1000 = 0.197 kN/m

2. 4 Nos 65NB (Medium) Pipe 4*6.42*10/1000 = 0.257 kN/m

Total 0.454 kN/m

c. Due to Future Overlay of Bituminous Wearing Coarse

=2.50*2.3*0.1*10 5.75 kN/m

Net Load : 5.750+0.454+2.461 = 8.665 kN/m

Selfweight of the truss is inserted in the analysis through the use of "SELFWEIGHT" command of STAAD. However, the total load is increased by 7% to take care of the gussets, joints & variation in member weights due to rolling margin, which otherwise is not accounted for.

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Page 32 of 63

4.4 Live Load

Impact factor: 1.154

(refer IRC:6-2000 cl.211.2 and figure 5.) 4.5 Seismic Load

6. Calculation of Actions Due To Seismic Load 6.01

Arunachal Pradesh Section is in Seismic Zone V

Type of Soil Medium Soil

= Horizontal Seismic Coefficient = 0.18

= Vertical Seismic Coefficient = 0.09

Z = Zone factor = 0.36

I = Importance factor = 1

R = Response reduction factor = 2.5

Sa/g = Average response acceleration coefficient = 2.5

(depending upon fundamental time period T)

T = Fundamental Time Period = 0.33 sec

2.0*sqrt(D/1000F)

F = Horizontal Force in KN required to be applied = 68.7 t

at the centre of the superstructure for 1mm deflection at the top of pier/abutment

 = Deflection at the top of Pier/abutment = 1 mm

I = Moment of Inertia of the Pier/Abutment = 0.785

d = Diameter of the Pier/Abutment = 2.0 m

G = Grade of Concrete for Pier/Abutment = M20

E = Modulus of Elasticity of Concrete = 25491.17 Mpa

5700*sqrt(fck) as per IRC:18,2000 Cl:10.2

= 3.15E+06 t/m^2

Since the other type of loads in 24R category are lesser in total weight & they are spread out over larger spaces also, we are considering 24R Tracked Vehicle only for live load actions, as this shall produce the most severe actions.

Live will be generated and applied for one lane Class 24R vehicle within the STAAD analysis on the top chord only. A_h (Z/2)*(S_a/g)/(R/I) A_v (6EI/L3₎ m4 (()*d4_/64)

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Page 33 of 63

L = Height of the Pier/Abutment above Fixity Level = 6.000 m

D = Appropriate Dead Load of the Superstructure = 1884.69 t

and Live Load TOTAL LOAD ON SUPERSTRUCTURE

Top Chord : 63.428 kN Bottom Chord : 63.428 kN Verticals : 29.436 kN Diagonals : 99.993 kN 13.082 kN 39.997 kN 112.956 kN 18.109 kN 1.466 kN

Total Steel Work: 441.895 kN

30.933 kN

Gross Weight : 472.828 kN

Deck Slab : 0.23182***40*10 = 477.556 kN

kerb, railing : (2.461+0.4536)*40 *2= 233.163 kN

Wearing course overlay : 11.2786726358056*40 = 451.14691 kN

Total Weight of the Structure Including SIDL: 1634.694 kN

Total Weight of the Structure Excluding SIDL: 472.83+477.56 = 950.384 kN

Vertical Short Member : Vertical Short Diagonal Member : Transversals (Bottom): Transversals (Top): Top Bracings :

Add 7% for gussets & Connections :

Refer sectional area of

corresponding member given in Property Calculation page

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Page 34 of 63

Live load arrangement on deck during earthquake:

3660 3660

30

40000

Maximum live load on the deck = 2*25 = 50 t

So, Live load on the bridge for seismic case: 0.5*50*10 = 250 KN

So, net horizontal seismic force:

0.18*(1,634.69+250) = 339.24 kN

So, seismic force on interior nodes: 339.24/32 = 10.60 kN

and that on end nodes: 10.60/2 = 5.30 kN

(Since the main contributor to this load is the concrete deck slab, so the force will be imposed on the mathematical model on the bottom chord nodes only)

25t

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Page 35 of 63

Note:-Assuming height of formation level from river bed =20.m Wind load on the structure :

Minimum bed level= 0

Hieght of formation level from river bed : 20.00m Formation level= 20

Depth of Slab : 200 mm

Depth of bottom Girder : 350 mm

Depth of top Girder : 350 mm

Depth of vertical member: 100 mm

Depth of diagonal member: 300 mm

Wind Speed at deck level : 136.00 kM/H Pressure at that level: 119

Wind Speed at a height of 23.00from bed level : 139.6 kM/H Pressure at that level: 126.5

Wind Speed at a height of 26.0m from bed level : 143 kM/H Pressure at that level: 136.6

So, Wind force on the deck = 0.065 t/m

& Wind force on top girder: 0.048 t/m

Height from river bed Wind Force

20.00m 0.042 t/m (on the bottom chord)

23.00m 0.013 t/m (on vertical member)

23.00m 0.041 t/m (on diagonal member)

26.00m 0.048 t/m (on the top chord member)

26.00m 0.014 t/m (on vertical member)

26.00m 0.041 t/m (on diagonal member)

= 300 kg/linear meter

= 0.3 t/linear meter

As per cl.212.6 of IRC:6-1966 minimum wind load on structure : 450 kg/linear meter

Wind Load (according to IRC:6-2000):

Wind load on exposed moving load (as per cl.212.4 of IRC:6-2000) :

As wind speed is more than 130km/hr no live load considered for wind load analysis.

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Page 36 of 63

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kg/m2

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5.0 Design of truss members

5.1 Recapitulation of member forces (From STAAD Output)

(Sign Convention: +ve : Compression, Sagging Moment, -ve : Tension, Hogging Moment)

(Values corresponding to live load case are inclusive of impact factor) a. Top Chord

Axial Shear _MidspanMoment_Support

(kN) (kN) (kN-m) (kN-m) N D 1 0 1 Selfweight of Truss Deadweight of deck slab Superimposed deadload Live load Seismic Horizontal Seismic Vertical Wind load N D 1 0 2 Selfweight of Truss Deadweight of deck slab Superimposed deadload Live load Seismic Horizontal Seismic Vertical Wind load N D 1 0 3 Selfweight of Truss Deadweight of deck slab Superimposed deadload Live load Seismic Horizontal Seismic Vertical Wind load Legend: b. Bottom Chord

Axial Shear _MidspanMoment_Support

(kN) (kN) (kN-m) (kN-m) N D 1 0 1 Selfweight of Truss Deadweight of deck slab Superimposed deadload Live load Seismic Horizontal Seismic Vertical Wind load N D 1 0 2 Selfweight of Truss Deadweight of deck slab Superimposed deadload Live load Seismic Horizontal Seismic Vertical Wind load N D 1 0 3 Selfweight of Truss Deadweight of deck slab Superimposed deadload Live load Seismic Horizontal Seismic Vertical ND 101 CL SYMM.

'ND' represents a segment, comprising of a "top chord", a "bottom chord", a "diagonal" and a "vertical member". The vertical member to the left of panel is a part of the segment under consideration.

ND 102 ND 103

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N D 1 0 3 Wind load

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c. Long Verticals

Axial Forces in (kN)

ND 101 ND 102 ND 103

Selfweight of Truss Deadweight of deck slab Superimposed deadload Live load

Seismic Horizontal Load Seismic Vertical Wind load d. Long Diagonals Axial Forces in (kN) ND 101 ND 102 ND 103 Selfweight of Truss Deadweight of deck slab Superimposed deadload Live load

Shrinkage Load Seismic Horizontal Load Seismic Vertical Wind load e. Short Verticals Axial Forces in (kN) ND 101 ND 102 ND 103 Selfweight of Truss Deadweight of deck slab Superimposed deadload Live load

Shrinkage Load Seismic Horizontal Load Seismic Vertical Wind load e. Short Diagonals Axial Forces in (kN) ND 101 ND 102 ND 103 Selfweight of Truss Deadweight of deck slab Superimposed deadload Live load

Shrinkage Load Seismic Horizontal Load Seismic Vertical Wind load

f. Transvarsals (at top)

Axial Forces in (kN)

ND 101 ND 102 ND 103

Selfweight of Truss Deadweight of deck slab Superimposed deadload Live load

Seismic Horizontal Load Seismic Vertical Wind load h. Top Bracings Axial Forces in (kN) ND 101 ND 102 ND 103 Selfweight of Truss Deadweight of deck slab Superimposed deadload Live load

Seismic Horizontal Load Seismic Vertical Wind load

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5.2 Calculation of Allowable Stresses a. Top Chord.

Permissible axial compressive stress in concrete: 5.0 MPa

(From IRC:21-2000 cl.303.1)

Permissible flexural compressive stress in concrete: 6.67 MPa

(From IRC:21-2000 cl.303.1)

Permissible axial tensile stress in concrete: 0.53 MPa

(From IRC:21-2000 cl.303.3) Permissible stresses in steel

Effective length of member: 5625= 5625 mm

5625= 5625 mm

Radii of gyration : 106.92 mm

99.27 mm

Maximum slenderness ratio: 5625/99.3 = 56.67

Allowable stress in axial compression : 175.34 MPa

Allowable stress for axial tension : 234.00 MPa

Flexural compressive stress: (in steel)

Allowable stress in bending tension: 241.80 MPa

Allowable stress for equivalent stress for combined actions: 358.80 MPa

Allowable average shear stress: 148.20 MPa

Allowable maximum shear stress: 167.70 MPa

b. Bottom Chord.

Effective length of member: 1875 mm

1875 mm

99.27 mm

Maximum slenderness ratio : 18.89

lxx =

lyy =

r_xx =

ryy =

 =

Since the top flange of the beam will be supported by the concrete deck throughout its length, so the allowable compressive stress shall be same as allowable tensile stress.

lxx =

l_yy =

rxx =

ryy =

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c. Verticals

6000 mm

19.67 mm

Allowable stress in bending compression: 241.80 MPa

d. Diagonals

Effective length of member: 4110.0 mm

4110.0 mm

98.85 mm

e Main Transversal at top Permissible stresses in steel

6000 mm

101.13 mm

lxx = l_yy = rxx = r_yy =  = lxx = l_yy = rxx = ryy =  = lxx = lyy = r_xx = ryy =  =

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f Bottom Transvarsals Permissible stresses in steel

6000 mm

31.99 mm

Allowable stress for bending compression tension : 257.40 MPa

I. Top Bracing Member. Permissible stresses in steel

4110 mm

150.07 mm

Note:-All the allowable stresses will be increased by 25% incase of wind load is considered and 40% when seismic load is considered.

l_xx = l_yy = rxx = r_yy =  = lxx = lyy = rxx = r_yy =  =

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7.0 Check for truss during construction stage

Modified forces in the members: Top Chord:

Axial Moment Shear

Selfweight 0.0 0.0 0.0

0.0 0.0 0.0

Allowable stresses in top chord:

Effective length of member: 2500

2500 Radii of gyration : (0.000/0.009)^0.5*1000 = 74.41 (0.00004/0.009)^0.5*1000 = 66.24

Maximum slenderness ratio: 37.74

Allowable stress in axial compression : 213.39 MPa Allowable stress for axial tension : 234.00 MPa

During construction, it is assumed that the 40% of the deck shall be supported by the top chord of the truss & the rest by proper & adequet arrangement of propping from the top transversals & bottom chord.

Additionaly, construction stage loading of 150kg/m2_{is also considered.}

Weight of the green concrete

=(2.6/2.5)*corresponding values of member forces for deck loading

Construction Stage Loading

=(1.5/2.5)*corresponding values of member forces for deck loading

Other members will not be checked as they are already safe with much higher loads & without any change in properties.

l_xx = l_yy = r_xx =

r_yy =

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Calculation of allowable stress in bending compression: 58.9 mm 191.1 mm D = 250 mm T = 17.2 mm 2125 mm 66.2 mm 1.0 0.005 -1 Y= = 26.5*10^5/(2125/66.2)^2 = 2575 X = = 2575*sqrt(1+(2125/20)*((2125*17.2)/(66.2*250))^2) = 58642 = 1*(58642-1*2575)*(59/191) = 17264 Allowable stress in bending compression: 164.00 Allowable stress in bending tension: 241.80

Allowable average shear stress: 148.20

Allowable maximum shear stress: 167.70

Actual Stresses:

Axial: (0.0+0.0+0.0)/(0.0086*1000) = 0.00 Flexural Tension : (0.00+0.00+0.00)/(-0.0002*1000) = 0.00 Flexural Comp. : (0.00+0.00+0.00)/(0.0008*1000) = 0.00 Shear: (0.00+0.00+0.00)/(0.00858496*1000) = 0.00

Net Stresses: (max) 0.00+0.00 = 0.00

(min) 0.00+0.00 = 0.00

All stresses are within the allowable limit. Hence, OK. c₁ = c₂ = l = r_y = k₁ =



= k₂ = f_cb =

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mm mm mm mm During construction, it is assumed that the 40% of the deck shall be supported by the top chord of the truss & the rest by proper & adequet arrangement of propping from the top

=(2.6/2.5)*corresponding values of member forces for deck =(1.5/2.5)*corresponding values of member forces for deck

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MPa = 2575*sqrt(1+(2125/20)*((2125*17.2)/(66.2*250))^2) = MPa MPa MPa MPa MPa MPa MPa MPa MPa MPa MPa MPa

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DESIGN OF CONNECTION Dia of bolt= 20 Bolt capacity Singel shear= 3.4 Double shear= 6.8 1) BOTTOM CHORD 0.0101

Maximum force carried by the member= 244.218

No of bolts required= 36.2 Provide= 32 Dia of bolt= 20 Bolt capacity Singel shear= 3.4 Double shear= 6.8 2) TOP CHOTD 0.0101

Maximum force carried by the top chord= 177

No of bolts required= 26 Provide= 28 Dia of bolt= 20 Bolt capacity Singel shear= 3.4 Double shear= 6.8 3) VERTICAL MEMBER 0.003472 81.2448 No of bolts required= 12 Provide= 10 Dia of bolt= 20 Bolt capacity Singel shear= 3.4 Double shear= 6.8

4) VERTICAL DIAGONAL MEMBER

0.007744 160

No of bolts required= 24

Provide= 22

Area of bottom chord=

Area of top chord=

Area of vertical member=

Maximum force carried by the vertical member=

Area of vertical diagonal member=

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Dia of bolt= 20

Bolt capacity

Singel shear= 3.4

Double shear= 6.8

5) TOP MAIN TRANSVERSE MEMBER.

0.00427 14 No of bolts required= 2 Provide= 4 Dia of bolt= 20 Bolt capacity Singel shear= 3.4 Double shear= 6.8

6) BOTTOM TRANSVERSE MEMBER.

0.00959288 91.13236 No of bolts required= 13 Provide= 14 Dia of bolt= 20 Bolt capacity Singel shear= 3.4 Double shear= 6.8

7) TOP BRACING MEMBER.

0.0001136 2.65824

No of bolts required= 0.3938

Provide= 4

Area of transverse member=

Maximum force carried by the transverse member=

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DESIGN OF CONNECTION mm ton ton m2 ton nos nos mm ton ton m2 ton nos nos mm ton ton m2 ton nos nos mm ton ton m2 ton nos nos

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mm ton ton m2 ton nos nos mm ton ton m2 ton nos nos mm ton ton m2 ton nos nos

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7.0 Design of end cross girder for jack-up condition

1) Reaction on each each bearing= 409 KN

centre line.

409 kn 6 m 409 kn

0.45

A B

5.1 m Design of end cross girder.

a) Reaction on each bearing. 409 kn

b) Support moment= 184 knm

c) Maximium mid span moment= 184 knm

d) Maximum shear force= 409 kn

Zxx required for the section= 760559 Using ISMB 550 as end cross girder.

Zxx of the girder= 2359800

Now maximum bending tensional stress= 78 mpa

Now maximum compression stress= 78 mpa

Hence provide ISMB 500 as end cross girder.

Dia of bolt= 20 mm

Bolt capacity

Singel shear= 3.4 ton

Double shear= 6.8 ton

Maximum shear force of the member= 409 kn

41 ton

No of bolts required 6.05 nos

Provide 8nos bolt.

It is assumed that the superstructure will be needed to be lifted off the bearing for bearing replacement. The jacks shall be placed below the transverse member at the end. For this purpose the location of these jacks alongwith their capacity shall have to be engraved on the location proposed.

mm3

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It is assumed that the superstructure will be needed to be lifted off the bearing for bearing replacement. The jacks shall be placed below the transverse member at the end. For this purpose the location of these jacks alongwith their capacity shall have to be engraved on the location

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8.0 Connection Design

a. Splicing of 300x300x12 box used as top chord.

C/s Area: 101

Reduction for holes: 28*2.2*12 = 73.92

Net Area: 138.24-73.92 = 27.08

Allowable stress in compression in the BOX: 175.34 MPa So, total maximum load that the section can take :

64.32*100*137.45/1000 = 474.8095 kN

in shear: 0.33*250 = 82.5 MPa

in bearing: 0.67*250 = 167.5 MPa

& in bearing =167.5*12*22/1000 = 44.22 kN

So, bolt value: 44.22 kN

No. of bolts required: 474.809451207655/44.22 = 10.7 Nos.

say 20 Nos.

Thickness of the cover plate required = 6432/(1200-26*2.2) = 8.00mm on both side. So, provide 12mm thick cover plate on both side..

b. Splicing of 300x300x12 box used as bottom chord.

C/s Area: 101

Reduction for holes: 32*2.2*12 = 84.48

Net Area: 138.24-84.48 = 16.52

Allowable stress in tension in the BOX: 234.00 MPa

So, total maximum load that the section can take :

53.76*100*150/1000 = 386.568 kN

in shear: 0.33*250 = 82.5 MPa

in bearing: 0.67*250 = 167.5 MPa

& in bearing =167.5*12*22/1000 = 44.22 kN

So, bolt value: 44.22 kN

No. of bolts required: 386.568/44.22 = 8.7 Nos.

say 20 Nos.

The arrangement of bolts (using 4 bolts in one row) in the joint

Thickness of the cover plate required =5376/(1200-32*22) = 8mm.plate on both side. So, provide 10mm thick cover plate on both side..

cm2

Assuming the BOLT shall all be site installed. So, the allowable stresses for bolts are (as per IRC:24-2001):

So, bolt resistance in double shear = 2*82.5*/4*222_{/1000 = 62.72 kN}

cm2

Assuming the BOLT shall all be site installed. So, the allowable stresses for bolts are (as per IRC:24-2001):

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Axial compression (Table 11.1 of IRC:24-2001) Bending compression (Table 8.2 of IRC:24-2001) 250 340 400 250 340 10 150 204 239 20 13 13 20 148 201 235 30 19 19 30 145 194 225 40 25 26 40 139 183 210 50 31 31 50 132 168 190 60 36 37 60 122 152 168 70 41 43 70 112 135 147 80 46 48 80 101 118 127 90 51 54 90 90 103 109 100 55 59 100 80 90 94 110 60 64 110 72 79 82 120 64 68 120 64 69 71 130 67 73 130 57 61 62 140 71 77 140 51 54 55 150 74 81 150 45 48 49 160 78 85 160 41 43 43 170 81 89 170 37 38 39 180 84 93 180 33 34 35 190 87 97 190 30 31 31 200 89 100 200 28 28 28 210 92 103 210 25 26 26 220 94 106 220 23 24 24 230 96 110 230 21 22 22 240 99 113 240 20 20 20 250 101 115 250 18 18 19 260 103 118 270 104 121 280 106 123 290 108 126 300 110 128 310 111 130 320 113 133 330 114 135 340 115 137 350 117 139 360 118 141 370 119 143 380 120 144 390 121 146 400 122 148 420 124 151 440 126 154 460 128 157 480 130 159 500 131 162 520 133 164 540 134 166 560 135 168 580 136 170 600 137 172 F_y = f_y l = l/r fcb

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620 138 174 640 139 175 660 140 177 680 141 178 700 142 180 720 143 181 740 143 182 760 144 184 780 145 185 800 145 186 850 147 188 900 148 191 950 149 193 1000 150 195 1050 151 196 1100 152 198 1150 152 199 1200 153 200 1300 154 203 1400 155 205 1500 156 206 1600 157 208 1700 157 209 1800 158 210 1900 158 211 2000 159 212 2200 160 213 2400 160 215 2600 161 216 2800 161 216 3000 161 217 3500 162 218 4000 163 219 4500 163 220 5000 163 221 5500 163 221 6000 164 222

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Bending compression (Table 8.2 of IRC:24-2001)



1 0.9 0.8 0.7 0.6 400 1 1 1 0.9 0.8 13 19



11473613 22947226 0.5 26 1 0.5 0.5 0 32 0.9 0.4 0.4 -0.2 38 0.8 0.3 44 0.7 0.2 49 0.6 0.1 55 0.5 0 60 0.4 -0.2 65 0.3 -0.4 70 0.2 -0.6 75 0.1 -0.8 80 0 -1 84 89

93 Axial stress: (top chord)

97 50 60 190 168 175.34

102 30 40 225 210 213.39

105 40 50 210 190 206.84

109 Axial stress: (bottom chord)

112 10 20 239 235 235.44

116 Axial stress: (tension tie) 119

122 Bending compression (tension tie):

126 6000 0 164 0 -1790.2719

129 6000 0 164 0 -143.87455

132 Axial compression (truss):

135 250 0 18 0 -81.07

137 Bending compression (truss):

140 6000 0 222 0 86.065404

143 Axial compression (bracing):

145 10 20 204 201 201.51

148 180 190 34 31 32.60

150 180 190 34 31 31.74

152 60 70 152 135 142.46

155 Bending compression (bracing): 157

159 Bending compression (truss):

161 6000 0 222 0 -1249.0755 165 169 172 175 178 181 184 187 189 192 k₁ k₂

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194 196 198 200 202 204 205 207 208 210 213 216 219 222 224 226 228 230 233 236 238 240 242 243 245 246 248 250 251 252 253 255 257 258 259 259 260

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0.5 0.4 0.3 0.2 0.1 0

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