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Titleirc.gov.in.083.2014
TagsBearing (Mechanical) Friction Structural Steel Corrosion
File Size3.5 MB
Total Pages60
Document Text Contents
Page 1

IRC:83-2014 (Pt. IV)

STANDARDSPECIFICATIONS
AND

CODEOF PRACTICE
FOR

ROADBRIDGES

SECTION - IX
BEARINGS

(SPHERICAL AND CYLINDRICAL)
PART - IV

73

INDIAN ROADSCONGRESS
2014

Page 2

Digitized by the Internet Archive

in 2014

https://archive.org/details/govlawircy201483

Page 30

IRC:83-2014 (Pt. IV)

6 Co-relation factor for Welds, to be taken as 0.9

Y Partial factor of Safety

a
i.gb

b.gb

4i

5.6 Design Verification of Backing Plates

Both the sliding and the mating surfaces shall be supported by metal backing plates. In order
to avoid unacceptably small clearance due to deformation under loads and stresses at the
sliding interface, which could otherwise create unacceptably small clearance between the
adjacent backing plates and as a result, cease the Bearing rotation ability causing higher
wear, the clearance between the adjacent backing plates shall be checked.

However, in Spherical and Cylindrical Bearings, the flat sliding surface is confined/mounted
on a thick convex backing plate which apparently has high stiffness and rigidity against
deformations as shown in Fig. 9. Thus only the deformation "Aw,^^^" of the backing plates to
flat mating surface i.e. bearing top plate and concave sliding surface i.e. bearing bottom plate
shall be calculated separately as per the expression given in Clause 5.6.1 and both shall
satisfy the condition given below:

where.

Aw, , < Aw,
'act. — 'perms.

Aw, h ( 0.45 - 2 V (h/L) )'perms ^ \ / /

L diameter of the flat/concave Sliding Surface (mm)

h projection of the flat/concave Sliding Surface above the recess (mm)
L

. ^. ° > ^^^d ^'^^•V^'0/•V"'•J'd ''^•"•'••O ' " ^ '
"

Fig. 9 Deformations of Backing Plates

The stress in the backing plate induced by the respective deformation shall not exceed the
elastic limit in order to avoid permanent deformations.

5.6.1 Actual deformation of the backing plate

The maximum relative deformation "Aw,^^^" in the backing plate over the diameter 'L' shall be
calculated from the following expression:

0.55

where,

Aw = ——. k .a . k. . a.
T c c b b

= 1.1 +(1.7-0.85.d,/L).(2-d^/Lo) if L <d <2 L
0 — b — 0

22

Page 31

IRC:83-2014(Pt. IV)

1.1

N

if

sk,max
N

a. +

d >2
b

sk,perm

ce

= 0.30 + 0.55 . d /L

L

L + 2 • t
b J

3 • Lr
,0.4

where,

Diameter of the backing plate or 1 . 1 3 a^^ (a^ being the side of the square

plate or the minor side of the rectangular plate)

Thickness of the backing plate; for backing plates with a concave surface

the calculation may be based on the equivalent constant thickness t'^
t' =t, +0.6(t

b b, mm ^ K )b, max b, mm '

sk.max

sk.perm

L Diameter of the flat/concave Sliding Surface (mm)

L Reference diameter - 300 mm
Maximum Vertical Design Load in SLS condition

Vertical Load due to permanent actions in SLS condition

. Short term static modulus of elasticity of concrete i. e. 5000 V f^,^

Modulus of elasticity of concrete, for permanent load effects i. e. 1/3 E^

The structural concrete members to which the backing plates are attached shall be of min.
M35 Grade. Use of Mortar Layers between concrete and steel plate of equivalent or higher
strength than concrete is also allowed. Similarly material for steel backing plates shall be

steel grade having the yield strength as 340 MPa min.

The above also applies when using lower concrete strength classes and/or steel grades,
provided the "Aw.p^^^^." value as calculated above is reduced by a factor of:

0.90 when using concrete grade less than M 35 but limited to M 30

0.67 when using steel having yield strength less than 340 MPa but limited to
250 MPa

0.60 when using both concrete grade less than M35 and steel with yield strength
less than 340 MPa but both limited to minimum M 30 Grade and 250 MPa
respectively

5.6.2 Thickness of the backing plate

The thickness t^^.^ of the backing plate for concave sliding surface i.e. Bearing Bottom Plate

shall not be less than 12 mm.

23

Page 60

-I

(The Official amendments to this document would be published by
the IRC in its periodical, Indian Highways' which shall be

considered as effective and as part of the code/guidelines/manual,
etc. from the date specified therein)

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