Page 20 - Jabalpur_EQ

Introduction
Chapter 1

Figure A1-2. Rocking of a 10m
granary at Chhattarpur.

na

mg

Center of
rotation
1.0 m

Roof acceleration in a 2-Storey building in Amanapura

In Amanapura area, which was one of the most affected localities in the Jabalpur

city, ceiling fan hanging from the roof RC slabe was observed to swing so vio-
a
lently that its blades touched the ceiling. Dark brown paint marks could be easily
seen on the ceiling surface. If we neglect the angular momentum of moving fan
and friction in the hook, it can be thought as an accelerometer and its acceleration
can be given by (Fig. A1-3):

a = g tane (EQ A.2)
where is the angle of swing. Since half length of the blade was approximately

equal to the height of the fan, the rotation 6-45 and that means the roof accel-

Figure A1-3. Swinging of a
ceiling fan hanging from the
roof slab of a 2-storey (weak
RC frame with brick infills)
building which acts as a
"Classical Accelerometer."
2h

Jabalpur Earthquake of May 22, 1997 10