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Bearing Design Specifications

The document describes the design of a bearing for the Chawai bridge according to modified GAD input parameters. Key parameters include a maximum normal load of 765kN, minimum normal load of 600kN, and 8 internal elastomer layers. Calculations determine the effective bearing dimensions of 388mm width and 618mm length, with a total height of 144mm. Checks show the shape factor of 9.931 is not optimal, and the average compressive stress of 3.19MPa is not within specifications, requiring modification to the design.

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Priyanka Hui
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59 views2 pages

Bearing Design Specifications

The document describes the design of a bearing for the Chawai bridge according to modified GAD input parameters. Key parameters include a maximum normal load of 765kN, minimum normal load of 600kN, and 8 internal elastomer layers. Calculations determine the effective bearing dimensions of 388mm width and 618mm length, with a total height of 144mm. Checks show the shape factor of 9.931 is not optimal, and the average compressive stress of 3.19MPa is not within specifications, requiring modification to the design.

Uploaded by

Priyanka Hui
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as XLS, PDF, TXT or read online on Scribd
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DESIGN OF BEARING OF CHAWAI (AS PER MODIFIED GAD)

INPUT FOR BEARING DESIGN

Nmax (Maximum permissible normal load) = 765 KN

Nmin (Minimum permissible normal load) = 600 KN


n (number of internal elastomer layer) = 8

lo (overall length of bearing) = 630 mm

bo (overall width of bearing) = 400 mm

c (Side cover) = 6 mm

hi (Thickness of individual internal layer of elastomer) = 12 mm

he (Thickness of top/bottom outer layer of elastomer) = 6 mm

hs (Thickness of steel laminate) = 4 mm

a (Coefficient of thermal expansion) = 0.0000117

t (Average temperature) = 25 o
C
L (Length of Bridge expanding) = 9680 mm

Shrinkage coefficient = 0.0002

H (Horizontal load per bearing) (Braking + Siesmic+Temparature) = 11 ton

ad (Total angle of rotation due to load of the super structure) = 0.0032 rad
CALCULATIONS OF DIFFERENT PARAMETERS FROM INPUT FILE

b (Effective width of bearing) = 388 mm


l (Effective length of bearing) = 618 mm
h (total elastomer thickness) = 108 mm
h' (total hieght of bearing) = 144 mm
S (shape factor) = 9.931
Dbd (Translation in the direction of width) = 4.84 mm
A (effective plan area of bearing) = 239784 mm2
gd (shear strain of elastomer bearing) = 0.50 mm
sm (average compressive stress) = 3.19 Mpa
b (ratio) = 0.319
abi,max (maximum rotation of single internal layer of elastomer) = 0.001568
tc (Shear stress due to axial compression) = 0.482 Mpa
tg (Shear stress due to horizontal deformation) = 0.504 Mpa
ta (Shear stress due to rotation) = 0.8196 Mpa

CHECK FOR DIMENSION OF BEARING


S = 9.931 NOT O.K. Between 6 to12
CHECK FOR TRANSLATION DUE TO SHEAR STRAIN

gd = 0.50 mm ≤0.7
SAFE
CHECK FOR TRANSLATION DUE TO ANGLE OF ROTATION

ad = 0.0032
b.n.abi,max = 0.004
SAFE

CHECK FOR FRICTION & AVG. COMP. STRESS


gd = 0.504 mm
P = 0.519 >= 0.504
SAFE
sm = 3.19 Mpa Between 2 to10
NOT O.K.
CHECK FOR TOTAL SHEAR STRESS

tc + tg + t a = K = 1.8056 Mpa ≤5
SAFE

FINAL SIZE OF BEARING = 630 X 450 X 96MM

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