jsy vxznwr Transforming Railways

www.rdso.indianrailways.gov.in
 introducing the response reduction factors.
c) Different response reduction factors have been proposed for the different components
of the bridge, depending on the redundancy, expected ductility and over-strength in
them.
d) The design force level for bridge has been raised from the earlier level and brought in
line with IS1893(Part1):2002.
e) The concept of capacity design is introduced in the design of connections, substructures
and foundations.
f) The soil-foundation factor is dropped. The effect of soil on response is represented in
the response spectrum.
g) Provision for dislodging of girders in the bearings is introduced.
h) Use of vertical hold-down devices, stoppers, restrainers and horizontal linkage
elements to account for the large displacements generated during seismic shaking is
recommended for preventing falling of spans.
j) A minimum width of seating of superstructure over substructure to avoid dislodging of
spans from atop the substructure is required for all bridges.
k) The method of computing earth pressures for c- f soil is included in the section on
Retaining Walls

The units used with the items covered by the symbols shall be consistent throughout
this standard, unless specifically noted otherwise.

(A.K Dadarya)
ED/B&S/RDSO

2
EL2x + EL2y or EL2x + EL2y + EL2z

8
NOTE : In case of MCE, non-linear analysis and Tie History Method shall be adopted for
regular, special regular and special irregular bridges.

Z I Sa
Ah = . .
2 R g

10
p = 8.75 Ah Hy

17
 2
é ù
ê ú
Ca =
(1 ± Av )cos 2 (f - l - a ) ê
´ê
1 ú
1 ú
cos l cos a cos(d + a + l ) ê
2
ì sin(f + d )sin(f - i - l ) ü 2 ú
ê1 + í ý ú
ë î cos(a - i )cos(d + a + l )þ û
0

Æ
h

2
A
3 h

20
 (Ppg )dyn = 12 gh C p2

2
é ù
ê ú
2
(1 ± Av )cos (f + a - l ) ´ êê 1 ú
Cp = ú
cos l cos 2 a cos(d + a + l ) ê 1
ú
ê1 + ìí sin (f + d )sin (f + i - l ) üý 2 ú
êë î cos(a - i )cos(d - a + l )þ úû

qh cos a
(P )Aq = Ca
dyn
c o s (a - i )

q h co s a
(P )p q d yn =
co s (a - i )
C p

21
 é gs A ù
l = tan -1 ê ´ h ú
êë g s - 10 1 ± Av úû

22
 2c
Hc = Nj = nH
g

h'

cos a
2(Ca - Ka)
cos(a-i)

2(C'a - K'a) cos a

h'
h h cos(a-i)

h'

23
 Q(1±an)

D
q
Q.ah nH

C
I E
A i G
a H
K
a
F W.ah c.g

W.(1±ag)

q
H1

f
H
a
d

R
P

aq

B
Fig. 7 FORCES ACTING ON FAILURE WEDGE IN ACTIVE STATE FOR SEISMIC CONDITION IN C- f SOIL

1
A dyn
2
(
g H 2 N ag m )
dyn
(
+ qH N aqm )
dyn
- cH (N acm )dyn

é n cos i cos a ù
ê1 - cos (a - i ) ú
ë û

24
25
 (Naqm)st

f(Deg.)

9C (Naqm)st versus f for n = 0.4, i = 00

0
(Fig. 9 EARTH PRESSURE COEFFICIENT (Naqm)st for 0 SLOP
(Naqm)st

f (Deg.)
10A (Naqm)st versus f for n = 0, i = 100
(Naqm)st

f (Deg.)

10B (Naqm)st versus f for n = 0.2, i = 100

26
 (Naqm)st

27
f(Deg.)

40
 IRS Seismic Code: 2017

ANNEX A
(Clause 2)
LIST OF REFERRED INDIAN STANDARDS
456: 2000 Code of practice for plain and reinforced concrete (fourth revision)
1343: 2012 Code of practice for pre-stressed concrete (first revision)
1786: 2008 High strength deformed steel bars and wires for concrete reinforcement-
Specification (fourth revision)
1893 Criteria for earthquake resistant design of structures
(Part 1) : 2002 General provisions and buildings
(Part 2) : 2014 Liquid retaining tanks - Elevated and ground supported

ANNEX B
(Foreword, Clauses 4.2.7,5.3and 17.2)
DUCTILE DETAILING
B-O GENERAL
The detailing rules given have been chosen with the intention that reliable plastic
hinges should form at the top and bottom of each pier column , or at the bottom only of a
single stem pier under horizontal loading and that the bridge should remain elastic between
the hinges )see Fig. 13(. The aim is to achieve a reliable ductile structure. Repair of plastic
hinges is relatively easy.
Design strategy to be used is based on assumption that the plastic response shall occur in
the sub-structure.
B-1 SPECIFICATION
B-1.1 Minimum grade of concrete should be M25 (fck = 25 MPa).
B-1.2 Steel reinforcement having elongation more than 14.5 percent and conforming to
other requirements of IS 1786 shall be used.
B-2 LAYOUT
a) The use of circular column is preferred for better plastic hinge performance and
ease of construction .
b) The bridge must be proportioned and detailed by the designer so that plastic hinges
occur only at the controlled locations )for example pier column ends( and not in other
uncontrolled places.
B-3 LONGITUDINAL REINFORCEMENT
The area of the longitudinal reinforcement shall not be less than 0.8 percent and not
more than 6 percent of the gross cross-section area Ag . Splicing of flexural region is not
permitted in the plastic hinge region . Lap shall not be located within a distance of 2 times the

30
 IRS Seismic Code: 2017

maximum column cross-sectional dimension from the end at which hinge may occur. The
splices should be proportioned as a tension splice.
8-3.1 Curtailment of longitudinal reinforcement in piers due to reduction in seismic
bending moment towards top.
8-3.1.1 The reduction of longitudinal reinforcement at mid-height in piers should not be
carried out except in tall pier.
8-3.1.2 In case of high bridge piers such as of height equal to 30m or more, the reduction
of reinforcement at mid height may be done. In such cases the-following method
should be adopted:
a) The curtailment of longitudinal reinforcement shall not be carried out in the
section six times the least lateral column dimension from the location where
plastic hinge in likely to occur.
b) The interval between hoop ties is specified to be less than 150 mm in a
reinforcement position. The interval between hoop ties shall not change
abruptly, the change must be gradual.
8-4 TRANSVERSE REINFORCEMENT
The transverse reinforcement for circular columns shall consist of spiral or circular hoops.
Continuity of these reinforcements should be provided by either [see Figs. (14 a) and 14(b)]:
a) Welding - The minimum length of weld should be 12times the bar diameter and the
minimum weld throat thickness should be 0.4 times the bar diameter.
b) Lapping - The minimum length of lap should be 30 times the bar diameter and - each
EARTHQUAKE A-I
FORCE _~~~~

POTENTIAL PLASTIC
I I PILE CAP

PILE

ELEVATION SECTIONAA

a) SINGLE COLUMN OR PIER TYPE SUBSTRUCTURES

A--<
_ EARTHQUAKE

A--<
ELEVATION SECTION AA

b) MULTI-COLUMN OR FRAME TYPE SUBSTRUCTURES

Fig. 13 POTENTIAL LOCATION OF PLASTIC HINGES IN SUBSTRUCTURES

31
 IRS Seismic Code: 2017
0
end of the bar anchored with 135 hooks with a 10 diameter extension into the confined
core. Splicing ofthe spiral reinforcement in the plastic hinge region should be avoided.
In rectangular columns , rectangular hoops may be used. A rectangular hoop is a
0
closed stirrup, having a 135 hook with a 10 diameter extension at each end that is
embedded in the confined core Fig. 14 (c). When hoop ties are joined in any place other than
a corner the hoop ties shall overlap each other by a length 40 times the bar diameter of the
reinforcing bar which makes the hoop ties with hooks as specified above.
Joint portion of hoop ties for both circular and rectangular hoops should be staggered.
B-5 DESIGN OF PLASTIC HINGE REGIONS
B-5.1 Seismic Design Force for Sub-structure Provisions given for the ductile detailing of
RC members subjected to seismic forces shall be adopted for supporting components of the
bridge. Further, the design shear force at the critical section (s) of sub- structures shall be
the lower of the following :
a) Maximum elastic shear force at the critical section of the bridge component divided
by the response reduction factor for the components as per Table

135' BEND

CONTINNOUS BAR
OF DIAMETER d

a) WELDING IN CIRCULAR HOOPS b) LAPPING IN CIRCULAR HOOPS

~
// 1\.'>
~

'Z

c) RECTANGULAR HOOPS

FIG. 14 TRANSVERSE REINFORCEMENT IN COLUMN

32
 IRS Seismic Code: 2017

b) Maximum shear force that develops when the sub-structure has maximum moment
that it can sustain (that is the over strength plastic moment capacity as per 8-5.2) in single
column or single-pier type sub-structure, or maximum shear force that is developed when
plastic moment hinges are formed in the sub-structure so as to form a collapse mechanism in
multiple column frame type or multiple-pier type sub-structures, in which the plastic moment
capacity shall be the over strength plastic moment capacity as per 8-5.2.
c) In a single-column type or pier type sub- structure, the critical section is at the bottom
ofthe column or pier as shown in Figs.13(a). And, in multi-column frame-type sub- structures or
multi-pier sub-structures, the critical sections are atthe bottom and/or top of the columns/piers
as shown in Figs. 13 (b).
8-5.2 Over Strength Plastic Moment Capacity
The over strength plastic moment capacity atthe reinforced concrete section shall
be taken as 1.3 times the ultimate moment capacity based on the usual partial safety factors
recommended by relevant design codes for materials and loads, and on the actual
dimensions of members and the actual reinforcement detailing adopted.
8-5.3 Special Confining Reinforcement
Special confining reinforcement shall be provided at the ends of pier columns where plastic
hinge can occur. This transverse reinforcement should extend for a distance from the point
of maximum moment over the plastic hinge region over a length 10 , The length 10 shall not
be less than , 1.5 times the column diameter or 1.5 times the large cross sectional dimension
where yielding occurs, 1/6 of clear height of the column for frame pier (that is when hinging
can occur at both ends of the column) , 1/4 of clear height of the column for cantilever pier
(that is when hinging can occur at only one end of the column)or600 mm.
8-5.4 Spacing of Transverse Reinforcement
The spacing of hoops used as special confining reinforcement shall not exceed 1/5 times
the least lateral dimension of the cross-section of column or 6 times the diameter of the
longitudinal bar or 150 mm.
The parallel legs of rectangular stirrups shall be spaced not more than 1/3 of the smallest
dimension of the concrete core or more than 300 mm centre to centre. If the length of any
side of the stirrups exceeds 300 mm, a cross tie shall be provided. Altematively, overlapping
stirrups may be provided within the column.
8-5.5 Amount ofTransverse Steel to be Provided
8-5.5.1 The area of cross-section, Ash, of the bar forming circular hoops or spiral , to be
used as special confining reinforcement, shall not be less than

A sw = 0.09SD k [ Ag _ 1.0 ] fck

Ac fy

fck
Asw = 0.024SD k - f-
y

33
 IRS Seismic Code: 2017

whichever is the greater

where
ASh = area of cross-section of circular hoop;
S = pitch of spiral or spacing of hoops, in mm;
Ok = Diameter of core measured to the outside of the spiral or hoops, in mm ;
fck = characteristic compressive strength of concrete ;
fy = yield stress of steel (of circular hoops or - spiral);
Ag = gross area of the column cross-section ; and
Ac = Area of the concrete core = ~ D;
4
8-5.5.2 The total area of cross-section of the bar forming rectangular hoop and cross
ties , ASh to be used as special confining reinforcement shall not be less than

_O.24Sh [Ag
A,.,- --;;/ - 1.0] -I ,.
• I"
Or

A,w = 0.096Sh I ,.
Where I"
h = longer dimension of the rectangular confining
Ak = hoop measured to its outer face ; and area of confined core concrete in the
rectangular hoop measured to its outer side dimensions.
NOTE - Grossties where used should be of the same diameter as a peripheral hoop bar and Ak shall be measured as the
overall core area, regardless the hoop area. Th e hooks of cross ties shall engage peripheral longitudinal bars.

8-5.5.2.1 Unsupported length of rectangular hoops shall not exceed 300 mm

8-5.5.3 For ductile detailing of hollow cross-section of pier, special literature may be
referred .
8-6 DESIGN OF COMPONENTS 8ETWEEN THE HINGES
Once the position of the plastic hinges has been determined and these reg ions
detailed to ensure a ductile performance, the structure between the plastic hinges is
designed considering the capacity of the plastic hinges. The intention here is,
a) to reliably protect the bridge against collapse so that it shall be available for service
after a major shaking.
b) to localize structural damage to the plastic hinge regions where it can be controlled
and repaired .
The process of designing the structure between the plastic hinges is known as 'capacity
design'.
8-6.1 Column Shear and Transverse Reinforcement
To avoid a brittle shear failure , design shear force for pier shall be based on over
strength moment capacities of the plastic hinges and given by:

VII
I M'
= -"""- -
II

34
 IRS Seismic Code: 2017
Where
~M ' = sum of the over strength moment capacities of the hinges resisting lateral loads,
as detailed. In case of twin pier this would be the sum of the over strength moment
capacities at the top and bottom of the column . For single stem piers the over
strength moment capacity at the bottom only should be used.
h = clear height ofthe column in the case of a column in double curvature; height to be
calculated from point of contra-flexure in the case of a column in single curvature.
Outside the hinge regions, the spacing of hoops shall not exceed half the least lateral
dimension of the column or 300 mm.

B-7 DESIGN OF JOINTS

Beam-column joints should be designed properly to resist the forces caused by axial
load , bending and shear forces in the joining members. Forces in the joint should be
determined by considering a free body of the joint with the forces on the joint member
boundaries properly represented .
The joint shear strength should be entirely provided by transverse reinforcement.
Where the joint is not confined adequately (that is where minimum pier and pile cap width is
less than three column diameters) the special confinement requirement should be satisfied.

35
 IRS Seismic Code: 2017

ANNEX C
(Clause 22.1.1.1)
GRAPHICAL DETERMINATION OF DYNAMIC ACTIVE EARTH PRESSURE

C-I MODIFIED CULMANN'S GRAPHICAL CONSTRUCTION (see Fig. 15)

Different steps in modified construction for determining dynamic active earth pressure
are as follows:
a) Draw the wall section along with backfill surface on a suitable scale.

b) Draw BS at an angle (<I> - '1') with the horizontal.

c) Draw BL at an angle of (90 - a. - 8 - '1' ) below BS.
d) Intercept BD1 equal to the resultant of the weight W1 of first wedge ABC ( and
inertial forces (±W1Uv and W1Uh).
The magnitude of this resultant is WI
W = WI J(Ha.,) +0.:
e) Through D1 drawD1 E1 parallel to BL intersecting BC1 at E1.
f) Measure D1 E 1 to the same force scale as BD1. The D1 E 1 is the dynamic earth
pressu re for trial wedge.
g) Repeat steps (d) to (f) with BC2, BC3, etc, as trial wedges .
h) Draw a smooth curve through E1 , E2, and E3.This is the modified Culmann's line.
j) Draw a line parallel to BS and tangential to this curve. The maximum coordinate in
the direction of BL is obtained from the point of tangent and is the dynamic active
earth pressure (PA)dyr.

2( Ca -Ka ) h' -.::..:r-=---,., MODIFIED

h' CULMANN'S LINE

FIG. 15 MODIFIED CULM ANN 'S CO NSTRUCTION FOR D YNAMIC A CTI VE EARTH PRESSURE

36
 IRS Seismic Code: 2017

ANNEX D
(Clause 22.1.2.1)
GRAPHICAL DETERMINATION OF DYNAMIC PASSIVE EARTH PRESSURE
0-1 MOOIFIEOCULMANN'SGRAPHICAL CONSTRUCTION
For determining the passive earth pressure draw BS at (<1>-'1') below horizontal. Next
draw BL at (90 - a - 0 - 'I' ) below BS. The other steps for construction remain unaltered
(see Fig. 16).
Effect of uniformly distributed load and line load on the back fill surface may be
handled in the similar way as for the static case.

MODIFIED
CULMANN'S LINE

ASSUMED PLANE
OF RUPTURE

S
MINIMUM PASSIVE ..::,.
PRESSURE VECTOR

FIG . 16 MODIFIED CULMANN'S CONSTRUCTION FOR DYNAMIC PASSIVE EARTH PRESSURE

37