Abstract:
Pakistan lies in a seismically active zone at the adjoin region of the three tectonic plates,
Indian at the east, Eurasian at west and Arabian at the south. The conferment is that most of
our region lies on ACTIVE fault lines. Thus Pakistan is considered amongst one of the high
seismic zones area in global map.
The structures built in such high seismic zones require a solid and concrete seismic analysis.
This can be performed by the method of equivalent static analysis, response spectrum analysis
and time-history analysis. In Pakistan, the orthodox method used is the equivalent lateral force
method. Equivalent lateral force method, consider the seismic loading as static. For low rise
building this is adequate however for medium to high rise building this does not suffice.
To achieve a reliable, better and seismically safe structure the design must cater the
dynamic nature of the load; the two methods that does this are the response spectrum and time
history analysis. Thus for the analysis of a hypothetical structure, the earthquakes to be
considered are the El-Centro, Mexico earthquake and the disastrous earthquake of Abbottabad
in 2005. The seismograph values of 08th October 2005 Azad Kashmir near Abbottabad base
station has been selected by comparative studies.
A 6 story hypothetical structure of 144 ft. x 76 ft. is considered and all three analysis
techniques are applied and a comparative study of different important parameters is carried out
including story displacements, base shear. The structure is analyzed using the software ‘CSI
ETabs 2015' and load combinations of all three types of loadings are separately applied on the
structure. The results obtained from all these methods are tabulated and graphically plotted for
a better analysis.
The base shear on resulting on a nonlinear model are quite less than those occurring in a
linear one hence it can be determined. The Story Displacements showing as a result of Time
History Analysis are higher than the other (conventionally used) methods. Showing that the
Time history analysis is the best option to cater for these large displacements
