GOVERNMENT OF INDIA

MINISTRY OF RAILWAYS

GUIDELINES
FOR
PROVISIONS OF OHE MAST
FOR
ELECTRIFICATION AT NEW AND EXISTING BRIDGE
PIER/ABUTMENT

Issued by

BRIDGES & STRUCTURES DIRECTORATE

RESEARCH DESIGNS & STANDARDS ORGANISATION
MANAK NAGAR,
LUCKNOW-226011
[web site : www.rdso.indianrailways.gov.in]
(For official use only)

OCTOBER -2015
0
1
 Provision of OHE MAST Arrangement at the Bridge Pier/Abutment

1.0 Design Loading on Mast: The Bridge Pier must be checked for design
loads on OHE Mast

All OHE masts are required to support overhead equipment consisting of

catenary wire, contact wire and droppers. In addition, masts may also be
required to carry return conductors, earth wire and 25 kV feeder wire.

The loads acting on the mast are as under:

1.1 Permanent Loads

1.1.1 Permanent Load (Vertical):

1.1.1.1 Dead load of overhead equipment consisting of catenary wire, contact wire
and droppers which is generally 1.6 kg/m length of overhead equipment.
1.1.1.2 Dead load of swiveling bracket, assumed to be 60 kg.
1.1.1.3 Dead load of earth wire (if any).
1.1.1.4 Dead load of return conductor and insulator for return conductor (if any).
1.1.1.5 Dead weight of any 25 kV feeder and insulator for the feeder (if any).
1.1.1.6 Dead weight of any small part steel work.
1.1.1.7 Self weight of mast.

1.1.2 Permanent Loads (horizontal):

1.1.2.1 Radial pull of contact and catenary wires caused by curvature of the track
and/or stagger of wires.

1.1.2.2 Radial pull of earth wire, return conductor if any and/or 25 kV feeder (if any)
caused by the curvature of track.

All Vertical permanent loads act perpendicular to the track. The only
horizontal permanent force acting parallel to track is the component of radial
pull due to swing of bracket. It may be noted that the swiveling bracket
remains in the normal position only at the mean temperature, if the overhead
equipment is regulated. In case of unregulated overhead equipment the
swing of the cantilever need not be considered.

2
1.2 Occasional Loads

1.2.1 Occasional Loads (Vertical):

The only occasional load acting vertically is the weight of a workman

assumed as 60 kg acting at the end of the bracket

1.2.2 Occasional loads (Horizontal)

The only occasional horizontal loads are due to wind, blowing perpendicular
or parallel to the track on the structure, steel work and wires. The two
conditions of wind being parallel or perpendicular to track are to be
considered separately. The assumed direction of the wind determines
whether the loads will be acting perpendicular or parallel to the track.

The moments at the top of foundation level under different conditions i.e. with
and without occasional loads, with wind blowing perpendicular or parallel to
the track are calculated by multiplying the above loads with the appropriate
lever arm.

To estimate the loads, it is necessary to know the extreme range of

temperature and wind pressure for which the overhead equipment may be
designed. It may be necessary to make reference to the meteorological
department and ascertain the temperature range and wind pressure recorded
over a number of years. As per rules for opening of Railways the
conformation of the state government concerned has to be obtained for the
wind pressure adopted. IS: 875-(Part-3) - 1987 Reaffirmed -1997 "Code of
practice for Design Loads (Other Than Earthquake) for Building and
Structures". May be helpful in determining the wind pressure and correlating
wind velocity with wind pressure. .

1.2.2.1 WIND LOADS

Wind pressures for design of OHE structure and determination of spans are
based on IS: 875-(Part-3) - 1987 Reaffirmed -1997 "Code of practice for
Design Loads (Other Than Earthquake) for Building and Structures".
Accordingly, the standard wind pressures adopted are as follows for all new
works for different Zone as indicated in the specification:-

(i) Navy Blue Zone - 73 kg/m2

(ii) Yellow Zone - 105 kg/m2
(iii)Blue Zone - 136 kg/m2
(iv) Green Zone - 155 kg/m2
(v) Red Zone - 178 kg/m2
(vi) Hatched Red Zone - 216 kg/m2

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1.2.2.1.2 For working out wind load, 190% of projected area for the Rolled Structure
&Fabricated Structure and 75% of the projected area for conductors and
other circular members is to be taken into account.

1.2.2.1.3 The safety of structures are checked for two conditions (i) at 35°C
temperature and full wind pressure and (ii) at 4°C temperature and 20% of
the full wind pressure.
1.2.2.1.4 The maximum span should be restricted to 54 m for Red Zone and 63mfor
Navy Blue Zone. In case of curve on banks of such bridges, the span should
be 4.5 m less than the maximum span permitted by relevant span and

4
 stagger chart, but should not exceed 54 m for Red Zone and 63 m for Navy
Blue Zone. Structural design and analysis of steel masts is to be done as
per IS: 800-1984 "Code of practice for general construction in steel".

2.0 Locating OHE masts on Bridges

As per Ministry of Railways, Design Manual for Electric Traction, Volume 3,

Traction Overhead Equipment (July 1994), Chapter 3 Para 3.3.2:

“Span: The distance between the centerline of the adjacent supporting

structures for the overhead equipment/lines known as span.

The standard spans vary in steps of 4.5m from a minimum of 27m to a

maximum of 72m i.e. 27, 31.5, 36, 40.5, 45, 49.5, 54, 58.5, 63,67.5 and 72
m subject to para1.2.2.1.4.Standard spans shall be used to the extent
possible.

Where structures are located on the Bridge Piers/Abutments of Long

Bridges, the span shall be the distance between centers of Bridge
Piers/Abutments.

On main track, the lengths of two consecutive spans shall not differ by more
than 18m.”

Thus OHE Masts may be required to be located on Bridge Piers etc., if

unavoidable otherwise

3.0 Guidelines of Railway Electrification (RE) mast over the piers:

The Pier Top Length must have following minimum provisions to avoid
obstructions during Bridge rehabilitation, re-girdering and maintenance works
at Piers. Minimum clear distances for locating the OHE Mast base plates.

SN Type of Bridges Clearances Required Remarks

1 Steel Girder Bridges of Minimum 2450mm from Implantation of OHE
clear spans 12.2m and the Centre line of track to Masts to be decided
below (For likely the edge of Base Plate. after giving the
replacement of Girders minimum clearances.
with PSC slab Units)
2 Steel Girder Bridges of Minimum Implantation of Special arrangements
clear spans above OHE Masts shall be (Boom type) may be
12.2m (For likely re- 3600mm adopted.
girdering with new
Girder)
3 PSC Box/I Girder Minimum Implantation of Minimum clearance for
Bridges OHE Masts shall be any structure as per
2600mm from C/L of SOD
track

5
 TYPICAL DISTANCES FROM CENTRE LINE OF TRACK

150
OHE MAST
Y C/L OF TRACK
Z
X

700x700

ELEVATION

700
Min. 200mm
700

PLAN

FIGURE : 1

X 2600mm for PSC Box/I Girder Bridges.

2450mm for Steel Girder Bridges of clear spans12.2m and below.
3600mm for Steel Girder Bridges clear spans above 12.2m.
Y X + Width of base plate +200mm
Z = X + Width of base plate/2 – width of Mast/2

4.0 Provision of OHE support on Bridge Super Structure, if it is not possible

to provide OHE structure on the Piers.

4.1 In case of through type Steel Bridge, the cantilever assemblies which carry the
catenary and contact wire, may be fixed either to vertical member or to a drop
arm fixed to a cross girder depending upon the position of support required
and clearance available.

The strength of Bridge Super Structure to withstand the loadings on account

of the OHE structures should be checked and permission of the Chief
Engineer be obtained for adoption of any OHE support arrangement on the
Bridge Super Structure.

6
5.0 New Bridges: Provision of OHE Support on Bridge Substructure:-

The Bridge /Bridge Pier to be designed must have provisions for OHE Masts,
irrespective of whether Electrification is sanctioned or not. The following two
types of foundation arrangement may be considered to provide OHE masts on
pier top and abutment.

5.1 OHE Masts foundation (Gravity Type) on top of Piers and Abutments
with the OHE masts embedded in the concrete

The foundation is designed like pure gravity foundation except that tension is
not permitted in the base, i.e. the resultant of the vertical forces and moments
is not permitted to fall outside the middle third of the base of the foundation.
Adequate number of dowel bars is provided to have a proper bond between
the piers and foundation base. The foundation should be constructed clear of
the bearing arrangement for OHE masts. A typical design of Gravity Type
Foundation is at Annexure-I

5.2 OHE masts supported on Pier and Abutment by provision of base plate
connections and holding down bolts (Ragged type)

On piers and abutments, the OHE masts welded to base plate will be fixed
with holding down bolts (Ragged type). The minimum diameter of the holding
down bolts (Ragged type) should not be less than 22mm; however, it is
preferable to adopt a minimum diameter of 25mm in view of corrosion. The
length and diameter of the holding down bolts (Ragged type) are to be
decided, to meet the actual tension, shear and bond stresses. Holding down
bolts (Ragged type)
Should conform to IS: 2062-92 (Grade 'A') - "Steel for General Structural
Purposes-Specification".

Accordingly the holes for holding Base Plate of future OHE must be kept,
properly secured against intrusion of kankar, foreign bodies etc. The holdings
down bolts (Ragged type) are to be grouted in the core holes made in the
Piers/Abutments, by epoxy grouting containing minimum bond stress not less
than (M-20) concrete.

The diameter and length of core hole may be kept as 40 mm and 950mm
respectively. The length of core hole may be kept slightly more than the length
of the holding down bolt(Ragged type), say upto 50mm, for the working
convenience, a Typical Design Procedure is at Annexure-II. A Sample Design
Calculation is enclosed as Annexure- III.

For new Bridge Piers/Abutments, the drawing of the standard size of base plate i.e.
length, width & thickness and hole to hole pitch & edge distance of anchor bolt is
enclosed as Annexure -IV, which should be referred for making holes in the
piers/Abutments.

The Typical Drawing of OHE Structure mounted directly on Pier, enough space
at Pier top as per Eastern Railway Standard Type Drawing:

7
 S No Scenario of mounting of OHE Structure Template No
1 OHE Mast on bed block with RCC details, CAO 1
(Con)/ER Drawing No.- 145-99

5.3 New Bridge Piers/Abutments having the provisions for erection of OHE mast
in the approved drawings do not require separate approval of the competent
authority for the OHE mast on Bridge Piers/Abutments.
6.0 Existing Bridges: Provision of Foundation for OHE Masts on Bridge
Pier and Abutment:-
The approval of Chief Engineer/Chief Bridge Engineer should be obtained for
adoption of any foundation arrangement on the bridge Piers/Abutments for
supporting OHE masts.

6.1 If the space available on the Pier/Abutment is not adequate to

accommodate the concrete blocks foundation or the base plate with holding
down bolts, then following arrangements can also be adopted with the
approval of competent authority.
S No Scenario of mounting of OHE Structure Template No

1. Directly on Pier, enough space at Pier Top 2

2. Through 3 ISMC Channels, directly on Pier 3

3. Mast Fixing arrangement at Trestle Beam 4

4. Mast fixing arrangement directly on Channel 5
without any outside projection from Pier.
5. Out rigger arrangements with suitable steel
channel
5.1 On Concrete Pier 6
5.2 Concrete Pier Special Arrangement-1 7
5.3 Masonry Pier Special Arrangement- 2 8

6.2 Strengthening of Pier and Abutment for support Foundation of OHE

Masts
In each individual bridge, it has to be studied upto what depth below the
base plate/pier top/ abutment top, the uplift forces from the holding down
bolts may cause any tension/compression and shear stresses. In case of
weak concrete or masonry within this depth, the pier/abutment may be
strengthened by anyone of the following methods:-
(i) Cement pressure grouting
(ii) Epoxy grouting
(iii) Guniting
In case of stone masonry bridges and old concrete bridges, careful
inspection of abutment and pier should be done to check for any cracks or
loose masonry or broken concrete, cavities, cracks in joints, in the location
where the foundation for OHE masts is to be constructed.

8
 The work of rehabilitation of weak substructure should be undertaken with
prior approval of Chief Engineer/Chief Bridge Engineer.

S No Scenario of mounting of OHE Structure Template No

Strengthening Pier (Masonry/concrete) by

Concrete Column
1 Arrangement -1 9
2 Arrangement -2 10
3 Arrangement -3 11

6.3 Special Arrangements:

In case of space constraint to provide direct arrangements of OHE masts on
Base Plate, non-possibility of Out Rigger Arrangement due to lack of strength
at the Bed Block level, Side Strutting arrangement or Separate-Pile
Arrangements may also be considered:

S No Scenario of mounting of OHE Structure Template No

1 Side Strutting 12
2. Separate Pile arrangement 13

7.0 Miscellaneous Items

7.1 The earthing arrangement for the OHE Masts structure should be done as
per code for bonding and earthing for 25kV AC 50 Hz single phase traction
system Code No. ETI/OHE/71(11/90) with latest amendments issued by
RDSO.

7.2 The Authority for passing, supervision and Inspection must be as observed
for ‘Important’ Construction Site activities including,
a. the inspection of the existing masonry/concrete of the bridge pier/abutment
to decide whether rehabilitation is needed,
b. ensuring the depth of Excavated core holes in the piers and abutments,
c. approving all construction materials brought to site, including holding down
bolts(Ragged Type), anchor angle, epoxy grouting material, and
d. supervising the construction work of the foundation

7.3 All concrete works for foundation of OHE structures on bridges should
conform to IS: 456-2000 “Code of Practice for Plain and Reinforced
concrete”.

7.4 The procedure for inspection and Maintenance of foundation for OHE
structures on bridges should be similar as for bridge inspection and
maintenance by Engineering Department and general instruction to be
observed while working In electrified areas should be as per the provisions of
Indian Railways Way and Works Manual - 1983 and Indian Railways
Permanent Way manual-1986, in addition to the instruction, if any, issued by
the Chief Electrical Engineer and Chief Engineer.

9
8.0 Recommendations

There are several arrangement for the provision of the OHE masts
on bridges as discussed in this report. The suitability of
any arrangement is to be decided after a proper study of the individual
bridges, the bridge span, space constraint on bridge Super Structure and
Sub-structure, clearance (Mechanical and Electrical), the strength of
existing bridge to carry the additional loading due to the OHE
arrangement while ensuring the safety and economy aspects.

10
 Annexure-I

TYPICAL DESIGN PROCEDURE OF PURE GRAVITY TYPE FOUNDATION

V

H
M
A Embedment of OHE Mast

A
TOP OF PIER

ELEVATION B
SIDE VIEW

H
B

D
PLAN
FIGURE : 2

BM= Bending moment at top of foundation in kg-m.

V= Vertical load at top of foundation in kg.

H= Lateral load at top of foundation in kg.

A= 1.50m (as per drawing no.TI/DRG/CIV/FND/RDSO/00001/04/0 of sheet-

2)

σcb= Permissible bearing pressure of material below foundation base. This is

to be assumed as per the site condition.

M= Bending Moment at the bottom of foundation = (BM + H x A) kgm.

N= Total Vertical load (V+ weight of concrete block) kg.

M D
Eccentricity= e = ≤
N 6

N 6M
Maximum stress at base, P= + ≤ σcb(Permissible stress in concrete)
BD BD 2
NOTE:-Adequate number of dowel bar are to be provided to have proper bond
between the pier and the foundation base. A typical provision of Dowel
Bars is 20mm dia @ 300mm c/c with grip-length50 cm on either
direction.

11
 Annexure-II

TYPICAL DESIGN PROCEDUREOF BASE PLATE

When the bending moment is quite large compared to vertical load, the eccentricity
 M
e =  is also large. In such cases it will be economical to take advantage of holding
 V 
down bolt.
Depending upon the size of mast, assume the dimensions of base plate, the
location of holding down bolts and the permissible bearing pressure.

Assumed, Length of base plate =D

Width of base plate =B
Distance of bolt from edge = a
Maximum bearing pressure
at the edge of base plate = P
Bending moment =M
Vertical load =V

m m'

a C R
Q
P

(1-k)h kh
h
D

FIGURE : 3

Taking moment about a bolt we get,

1  kh 
× P × k × h × B ×  h −  = (V × C + M )
2  3
Then find the value of 'k' from above.

Equating the vertical forces to zero, find the value of‘T’ (Tension in bolt) from,
1
T +V = × k × h× B× P
2

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Find the value of stress (σst,cal) in steel bolt by assuming the modular ratio m as 18.

1− k
σ st ,cal = P × × 18
k
T
Area of steel bolt on one side =
σst ,cal

Arrive at the diameter of bolts by assuming the number of bolts on one side.

Assuming the concrete grout with M-20, the permissible bond stress,τbd
is0.8N/mm2 as per IS: 456-2000(Table - 21).

Tension force in one bolt (N)

Length of bolt (in mm)= + 150
0. 8 × circumference of bolt (mm)

The thickness of base plate will be designed to take the bearing pressure and
bolt tension acting as cantilever. The critical sections are m and m’.
BM at section m= T x lever arm
BM at section m’= [Q x R x R/2 + 1/2(P-Q) Rx 2/3 x R] B

Where Q is the stress (N/mm2)at the section m’, R is the distance of section m’
from edge of base plate.
Assuming the permissible bending stress σbt=157 N/mm2= 1601 kg/cm2 [IRS-SBC
Table No.2, for plate thickness > 20 mm].
Find the thickness of plate (t) from equation,
Bt2/6 x fb = BM at m or m’ whichever is higher.

Gusset Plate

Assume a gusset plate of height (E) and thickness (t). The critical point of BM in
gusset is at the face of the column flanges.

The load consists of the upward pressure on the base plate in the zone hatched
in fig. The intensity of pressure is shown in the pressure diagram.

13
The eccentricity (location from section m’) of resultant stress of trapezoidal
pressure diagram

R(2 P + Q)
e=
3( P + Q)

S
R

FIGURE : 4

Mmax =load x lever arm

 (P + Q ) 
 × R× S×e
=
 2 
Where S is the half width of base plate.

t×E×E
Section modulus of gusset plate at the end of flange of column, Z =
6

The maximum bearing stress, σsb,cal= Mmax/Z

This should be less than189N/mm2 = 1928 kg/cm2 [as per IRS-SBC, Table -2]

14
  (P + Q )  1
 × R×S×
.The maximum shear stress,τss,cal =
 2  t×E
This should be less than 102 N/mm2 [as per IRS-Steel Bridge Code Table-2
for thickness >20mm].

Provide necessary stiffeners across the gusset plate, of having thickness

equal to thickness of gusset plate.

Design of weld

Assuming all the vertical load is effective, the total force at the junction of
V M
column flange and gusset, F = +
2 Depth of column

F
Force per lineal cm of weld =
Length of weld

Force per lineal cm

Thickness of weld =
Permissible strength of weld

Note:- This methodology is only for a typical guidance. A detailed design,

considering all the data as per site requirement, has to be done

15
 Annexure-III

TYPICAL DESIGN CALCULATION FOR BASE- PLATE & HOLDING DOWN BOLT

1. Type of Mast = B-200

2(a) Length of Mast = 10.50 m
(b) Addl. Height of Super-mast = 0m
Total (a) + (b) = 10.50 m
(c) Intensity of wind = 155 kg/m2
(d) Depth of construction = 2.4 m Pier top to Rail level
(e) Height of contact wire = 7.905 m from Base plate
(f) Height of Catenary wire = 9.305 m from Base plate
(g) Distance of Con. Wire from mast = 2.75 m from C.L.
3. OHE spans on either side
(a) = 37.50 m
(b) = 40.08 m
(c) Av. span = 37.50 + 40.08 = 38.79m
2
4(a) Tension in Contact Wire = 1000 kg for Regulated OHE
(b) Tension in Catenary Wire = 1000 kg for Regulated OHE
(c) Degree of Curve = Nil
5. Radial Pull (Due to Staggering)
Contact Wire = 0.4 + 0.4 x1000
38.79
(Taking stagger +ve 200 mm in Push-off & -ve 200mm in Pull-Off position, based on
Para A4 of Annexure-A, design Document No: TI/Design/OHE/2013/00001 RDSO)
= 20.62 Say 21.00 kg
6. Load
(a) Weight of OHE @ 1.6 kg/m = 1.6 x 38.79 = 63 kg
(b) Weight of Bracket = 60 kg
(c) Weight of man on the Bracket = 60 kg
(d) Weight of mast @48.904 kg/m = 48.904x10.50 = 514 kg
(e) Weight of super-mast @ 40kg/m = 40.00 x 0.00 = 0 kg
(f) Weight of super-mast
Cantilever arm =0 kg
(g) Weight of RC wire =0 kg
(h Weight of base plate (=0.7x0.7x0.025x7850x2)say= 200 kg
TOTAL VERTICAL LOAD = 897 kg

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TYPICAL SKETCH OF OVER HEAD EQUIPMENT(OHE)

Catenary

Contact

2.75
10.50

9.305
Mast B - 200 7.905

Rail Level
2.400

28 mm HD Bolts - 6 Nos

ELEVATION OF PIER WITH OHE MAST

NOT TO SCALE

All Dimensions are in metres.

FIGURE-5

17
7. Wind Load = 155.00 kg/m2 (For Green Zone, as per IS: 875-1987
Part-3)
(a) On catenary wire (including 5% Wind load on dropper)
= 0.75 x 0.01054(diameter of catenary wire) x 155.00 x
38.79 x 1.05 = 50 kg
(b) On contact wire (including 5%Wind load on dropper)
=0.75 x 0.01224(diameter of contact wire) x 155.00 x
38.79 x 1.05 = 58 kg
(c) On RC wire =0 kg
(d) On bracket (say) = 40 kg
(e) On mast and super-mast = 0.00 kg
(i) Wind load on mast =0.200(width of mast)x 155.00 x 10.50 x 1.9(=190%)
= 619 kg
8. (a) Vertical Load and Bending Moment:-
SN. Details of load Weight (kg) Lever arm Moment
(m) (kg-m).
1. Wt. of man 60 2.75 165
2. Wt. of bracket 60 1.38 83
(=2.75/2)
3. Wt. of OHE 63 2.75 174
4. Wt. of mast 514 - -
5. Wt. of super-mast 0 - -
6. Wt. of cantilever 0 0.00 0
7. Wt. of RC 0 0.00 0
8. Wt. of base plate 200 - -
Total 897 422

(b) Horizontal Forces & Moments (Perpendicular to Track)

SN Force in kg Lever Moment

Arm(m) (kg-m)
1. Wind load on catenary wire 50 9.305 466
2. Wind load on contact wire 58 7.905 459
3. Wind load on mast 619 5.250 3250
(=10.5/2)
4. Wind on Radial pull Contact 21 7.905 166
5. RC 0 0.000 0
Total 4341

(9) Total Bending Moment

Perpendicular to the track = 4341 + 422 = 4763 kg-m
Parallel to Track = 5% of perpendicular to track bending moment = 239kg

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 (A) SAFETY OF THE CHANNEL OUTRIGGER ARRANGEMENT

Y
23
WIND
410

W
X
X X

M = 4763kg-m
Y
X V = 897 kg

All dimensions are in mm

FIGURE-6

ISMC CL of mast
105 X

410

B 490 X 805 400 500

ISMC 250

700

700

FIGURE-7

19
 (i) Weight of channel (2 nos.) = 30.6(Weight of ISMC-250x80 per m)x 2 x1.80
l

=110.16 (say 150 kg)

(ii) Moment at x-x, M = 897 x 0.700 + 150 x 1.80/2 + 4763 = 5526 kg-m

(iii) Properties of Channel, ISMC-250x80

A = 39.00 cm2
IXX = 3880 cm4
Iyy = 211 cm4
ZXX= 307 cm3
Zyy = 38.5 cm3

(iv) Moment of Inertia of combined section

IXX= 2 x 3880 = 7760 cm4
Iyy= 2[211 + 39 x (20.5 +2.3) 2]= 40969.52 cm4

(v) Section Modulus of combined section

Zxx= Ixx/y = 7760/12.5 = 620.8 cm3

(vi) Actual Bending stress

σsbx,cal = M/Zxx =5526x100/620.8 =890 kg/m2<2195 kg/m2 (as per
IS:800-2007,permissile bending stress = 1650x1.33 kg/cm2)

(B) HOLDING DOWN BOLT

Max. BM at X-X = 5526 kg-m = 552600 kg-cm

Compressive Force on column = 897 kg
Spacing between bolt = 0.49 m = 49 cm
Force in Bolt = 552600=11277.55 kg
49
Using no. of Bolt on Nos.on both sides
Axial compression forcein =149.5 kg

Force in each Bolt = 11277.55/3– 149.5 = 3609.6 kg

Say 3610kg
Permissible tension in each bolt = 1224 kg/cm2
3610
Area required = = 2.94 cm 2
1224
Provided diameter of holding down bolt = 28 mm
Provided area = 6.154 cm2> 2.94 cm2

20
Embedded Length of Bolt (Design Bond stress; M-20 As per 26.2.1 of IS 456:2000-
8.15kg/cm2)
3610
= =37.88cm
8.15 × 1.33 × 2.8 × 3.14
(Permitted Stress increased by 331/3 % when wind load is considered as per Annexure B .2.3, IS 456:200)
Total length of bolt = 37.88 +2.5 +25 +15 =80.38cm (Length of Bolt extended by
thickness of base plate =2.5cm,Depth of channel = 25cm and extra margin 15cm)

Hence provided embedment length = 90 cm

(C) DESIGN OF BASE PLATE

Max. Tension in each bolt = 3610 kg

Bending moment at critical section X-X = 3x3610x10.5 =113715 kg-cm

Permissible bending stress in plate = 1650 x1.33 = 2195 kg/cm2

Thickness required = Bt2/6 x fb= BM at critical section X-X

113715x6
t= = 2.10cm = 21mm
2195x70
Provide 25 mm thick Base plate.
Hence base plate size: 700mmx700mmx25mm

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REFERENCES:-

Following References has been used extensively:-

1) CORE, Allahabad, Ref. No. ELCORE/ALD/C&D/OHE/DESIGN/9/4/05, Dated: 25.04.05.

2) TI Directorate’s ‘Guidelines for Provision of Foundation for Masts and special portal of
overhead electric equipment on Bridges’ received vide their letter No.
TI/CIV/REWAR/15,Dated :10.03.15

3) Ministry of Railways Design Manual for Electric Traction Volume – 3, Traction

overhead Equipment July-1994 by RITES.

4) Northern Railway approved Plan No. MB-RE/UMB-44

5) Eastern Railway (Construction Department) Standard Type : CAO(Con) DRG No. 145-99

6) Code No. ETI/OHE/71(11/90) with latest amendments issued by RDSO: code for
bonding and earthing for 25KV AC 50 Hz single phase Traction system.

7) Proceedings Seminar of Chief Bridge Engineer, 11th& 12th September-2014, held at

IRICEN, Pune.

8) IRS: Steel Bridge Code (Reprinted-1977) A&C upto 20.

9) IS: 875-(Part-3)-1987 Reaffirmed-1997.

10) IS : 800- 1984

11) IS : 2062-2011

12) IS : 456-2000

Note: Codes/Specifications referred in this Guideline should be of latest edition with all
amendments.

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