TYPICAL DESIGN CALCULATION FOR BRIDGE MAST BASE PLATE & HOLDING DOWN BOLTS

ON BRIDGE NO-08 KM 2/18 CH:2/612.53,Pier 1,2,3,4 BRIDGE MAST (BM-200)

MAST CALCULATION
Legend:- Description Unit Factor Remarks
1 Safety Factor for wire kg/m 0.75 Sw
2 Safety Factor for mast kg/m 1.9 Sm
Basic Data
Weight of OHE kg/m 1.6
Weight of Bracket Assembly kg 60 Wbkt
Weight of Man kg 60 Wman
Tension in Each Conductor kgf 1000 Tohe
Dia of Catenary wire m 0.01054 Dcat
Dia of Contact m 0.01224 Dcon
Spans
At "A" m 38.2 L1
At "B" m 26.2 L2
Basic wind Pressure kgf/m2 178 IS875:PART-3
S.No Description Unit Calculation Reference
1 Type Of Mast B-200
A Length Of Mast m 11.50 Lm
Unit Weight of Mast Kg/M 61.20
2 Total Weight of Mast m 703.80 Wmast
B Additional Height of Super Mast m 0.00 Lsm
Total A+B m 11.50 Ltotal
C Intensity Of wind kg/m2 178.00 Wp
D Depth Of construction(Pier top to Rail Level) m 3.43 Dcons
E Height of contact wire from Rail Level m 5.50 Hcon
F Height of contact wire from base plate m 8.930 Hcon-bp= Dcons+Hcon
G Encumbrance 2.000 E
H Height of catenary wire from base plate m 10.930 Hcat-bp= Hcon-bp + E
J Distance of Contact wire from mast C.L (Imp.) m 3.55 Imp
3 OHE Span on either side of Mast
Average Span C m 32.20 (L1+L2/2)
4 Degree Of curve 0.00

5 Radial Pull (Due to Staggering ) Contact wire

Stagger A m -0.20 a
Stagger B m 0.20 b
Stagger c m -0.20 c
((StaggerA+StaggerB)/Ave. Span)x1000 kg -12.42 [(a+c)*AVERAGE
SPAN*T/1000
Say kg -12.00
6 VERTICAL LOAD
A Weight of OHE(Average Span x Weight of OHE) kg 51.52 Wohe
B Weight of Bracket kg 60.00 Wbkt
C Weight of man on the Bracket Kg 60.00 Wman
D Weight of mast kg 703.80 Wmast
E Weight of super mast@40kg/m kg 0.00 Wsm
F Weight of super mast cantilever arm kg 0.00 Wsm-ca
G Weight of RC Wire kg 0.00 Wrc
H Weight of Base plate (0.7x0.7x0.025x7850*2) kg 264.94 Wbp
TOTAL VERTICAL LOAD (A+B+C+D+E+F+G+H) kg 1140.26 Wtotal
TOTAL VERTICAL LOAD Say kg 1140.00 Wtotal

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Date: 2025.09.02
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7 WIND LOAD
A On catenary wire(Including 5% wind load on dropper
0.75x Dia of catenary wire x wp xAvg span x1.05 kg 47.57
B On Contact wire(Including 5% wind load on dropper
0.75x Dia of contact wire x WP xAvg span x1.05 Kg 55.25
C On RC wire kg 0.00
D On Bracket kg 40.00
E On mast and super mast kg 0.00
F Wind load on mast (0.2xWpxLmxsafety factor for mast) kg 777.86
8 A VERTICAL LOAD AND BENDING MOMENT
Weight
1 Weight of man kg 60.00
2 Weight of Bracket kg 60.00
3 Weight of OHE (Avg span x Weight of OHE) kg 51.52
4 Weight of mast kg 703.80
5 Weight of super mast kg 0.00
6 Weight of super mast cantilever kg 0.00
7 Weight of RC Wire kg 0.00
8 Weight of Base plate kg 264.94
TOTAL WEIGHT kg 1140.00 Fcom
LEVER ARM
1 Distance of Contact wire from mast C.L (Imp.) m 3.55
2 Distance of Contact wire from mast C.L (Imp.)/2 m 1.78
3 Distance of Contact wire from mast C.L (Imp.) m 3.55

MOMENT
1 man Kg-m 213.00
2 Bracket Kg-m 106.50
3 OHE Kg-m 182.90
4 mast Kg-m 0.00
5 super mast Kg-m 0.00
6 super mast cantilever Kg-m 0.00
7 RC Wire Kg-m 0.00
8 Base plate Kg-m 0.00
TOTAL WEIGHT kg-m 502.40
B HORIZONTAL FORCES AND MOMENTS(PERPENDICULAR
TO TRACK)
Weight
1 Wind load on catenary wire kg 47.57
2 Wind load on contact wire kg 55.25
3 Wind load on mast kg 777.86
4 Wind on Radial pull contact kg -12.00
5 RC
LEVER ARM
1 catenary wire m 10.93
2 contact wire m 8.93
3 mast= (Lmast/2) m 5.75
4 Wind on Radial pull contact m 8.93
5 RC m
MOMENT
1 Wind load on catenary wire= Kg-m 519.98
2 Wind load on contact wire= Kg-m 493.35
3 Wind load on mast= Kg-m 4472.70
4 Wind on Radial pull contact Kg-m -107.16
5 RC Kg-m 0.00
TOTAL kg-m 5378.87

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Date: 2025.09.02
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9 TOTAL BENDING MOMENT(Perpendicular to the track)= kg-m 5881.27
(total weight + total moment)
Parallel to track =5% of perpendicular to track bending kg 294.06
moment
Say kg 297.00
Moment at X-X,=(0.75xFcom+moment perpendiculat to track) Kg-m 6736.27 Mxx

B.HOLDING DOWN BOLT CALCULATION

moment at XX,M(0.75xFcom+moment perpendiculat to track) Kg-m 6736.27 Mxx
kg-cm 673627
Compressive Force on column kg 1140.00 Fcom
Lever arm (Spacing between tow different end Bolt ) cm 50.00 Lspacing
Force in Bolt= kg 13472.53 F=Mxx/Lspacingx100
Using no of bolt on oneside Nos 3.00
Both side Nos 6.00
Axial compression forcein one bolt= kg 190.00 Faxial= Fcom/no. of bolt
both side
Force in each bolt= kg 4300.84 Fbolt= F/3-Faxial
Say kg 4301.00
Permissible tension in each bolt kg/cm2 1224.00 As per RDSO Guideline for
Bridge mast calculation
Area required = cm2 3.51 Fbolt/1224
Provided diameter of holding down bolt mm 25.00 Dbolt
As per RDSO Guideline for
Provided area cm2 4.91 Bridge mast
calculation
is diameter of bolt safe(provided are >required area) or unsafe safe

Embedded Length of Bolt(Design bond stress; M-20 As per 26.2.1 of IS cm 50.55 As per RDSO Guideline for
456:2000-8.15kg/cm2)= Fbolt/(1.33x8.15xdia. of boltx3.14) Bridge mast calculation
(Permitted stress increased by 331/3% when wind load is
considered as per annexure B 2.3,IS456:200)
(Length of bolt extended by thickness of base plate=2.5cm,Depth of cm
channel=0cm and extra margin 68.05
15cm)
provided length cm 85 safe
C.DESIGN OF BASE PLATE CALCULATION
Max. Tension in each Bolt kg 4301.00 Fbolt
Bending moment at critical section X-X= 3xFboltX length of mast kg-m 24516 Mcritical
Permissible bending stress in plate(1650x1.33) kg/cm2 2195.00 As per RDSO Guideline for
Bridge mast calculation
Thickness required=Bt2/6xfb=DM at critical section X-X =suare root cm 0.98
[(Mcriticalxno. of bolt)/(2195xwidth of base plate)]

cm 0.98
Thickness required mm 9.80
Thickness provided mm 25.00 safe
Provide 25 mm thick Base Plate.
Hence Base Plate Size is 700mmx700mmx25mm
Note :Calculation is done, based on the reference of RDSO Guidelines Manual for Bridge mast.(June 2022)
page 17-23

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by MAYURESH ZAHID byAKHTAR
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Digitally signed

SH KUMAR
Date: 2025.09.02 AKHTAR Date: 2025.09.02
KUMAR 14:52:13 +05'30' 14:52:23 +05'30'