Abstract:
Earthquakes are one of the natural hazards that have potential to cause the
maximum damages. These ground shaking forces are random and unpredictable in
nature. Performance based design has gained a new dimension in the seismic design
philosophy wherein the near field ground motion (usually acceleration) is considered.
Earthquake loads are carefully modeled so as to assess the real behavior of structure
with a clear understanding that damage is expected but it should be regulated. The
recent advent of performance based design has brought the nonlinear static pushover
analysis procedure to the forefront. Pushover analysis is a static nonlinear procedure
in which the magnitude of the structural loading is incrementally increased in
accordance with a certain predefined pattern. With the increase in the magnitude of
the loading, weak links and failure modes of the structure are identified. The loading
is monotonic with the effects of the cyclic behavior and load reversals being
estimated by using a modified monotonic force deformation criteria and with
damping approximations. Static pushover analysis is an attempt by the structural
engineering profession to evaluate the real strength of the structure and it promises to
be a useful and effective tool for performance based design. This study focuses on
performance based design of three multistory RC framed buildings of Blue Area
Islamabad, Pakistan, subjecting them to monotonically increasing lateral forces with
an invariant height wise distribution until the preset performance level (target
displacement) is reached. Considering the deficiencies indicated in analysis, these
buildings were redesigned by adopting retrofitting techniques such as shear wall,
bracing and column strengthening. These techniques strengthened structures to reach
the targeted performance level.
