Page 72 - Jabalpur_EQ

Chapter 3 Brick Masonry & Reinforced Concrete Buildings

Figure 3-26. Typical damage to a mumty in Eastland of OFK campus.

ness (h/t ratio) was found to vary from 16 to 20 which is much larger than pre-
ferred value of 9 for top storey walls (BSSC 1992a). In any case, the slenderness
should be kept below 14 in a multi-storey buildings. Figure 3-26 shows a typical
damage to a mumty in the OFK campus where almost all buildings with similar
arrangements of mumties suffered similar damage.

For newer structures, isolating the stairs from the rest of the structures is a better
option or it should be built integrally with its lateral load resisting elements. Stair
wells should allow for inter-storey drift because they seismically interact with the
rest of the structure, if not isolated. For existing mumties bracing walls to reduce
the effective height and hence the slenderness of walls would reduce their vul-
nerability to out-of-plane forces. The location of stairwell in a structure also plays
a major role in its seismic performance. They are more troublesome when they
are located near the re-entrant corners as observed in New Hostel building at
Agriculture University. Brittle unreinforced masonry members fail, litter stairs
and corridors thus blocking exit paths.

PERFORMANCE OF MASONRY CHIMNEYS &
PARAPET WALLS
Failure of free standing compound walls, chimneys and parapet walls are phe-
nomena related to dynamic instability too. Damage to parapet walls was com-

Jabalpur Earthquake of May 22, 1997 62