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Chapter 3 Brick Masonry & Relnforced Concrete Bullding
Figure 3-5. Out-of-
plane damage to a URM
wall at the corner
The overturning forces developing in the wall above had to continue down to the
foundation through the columns in the first storey as shown in Fig. 3-8. These col-
umns were designed for vertical loads from gravity only and were easily over-
whelmed by axial loads imposed by four storey high walls. Figure 3-9 shows the
failed section of a first storey column of open bays near the first floor. Further
more, the lateral strength of the first storey would be less than 80% of the top sto-
reys due to open bays and therefore, the first storey was a weak storey.
The building was deficient in the strength of its first storey columns which sup-
port the brick infill walls from the floors above. Strengthening of the columns to
support the gravity plus overturning forces is the minimum effort needed for ret-
rofitting of the building. Also, the shear transferring ability of the diaphragm at
the level of discontinuity should be checked.
Jabalpur Earthquake of May 22, 1997 46
