RESPONSE SPECTRA CONSIDERING RECORDED GROUND ACCELERATIONS IN PAKISTAN

Abstract

: The large damage caused by October 08, 2005 Kashmir earthquake in Pakistan has
raised several questions on the current design techniques and construction practices in the country.
Realizing the enormity of the situation, the Government of Pakistan selected a committee of technical
experts to provide guidance for the revision of the country’s Building Code. Pakistan has now been
classified into various seismic zones according to Building Code of Pakistan (BCP-07). BCP-07 now
encompasses seismic provisions. Seismic Provisions used in BCP-07 are extracted from Uniform
Building Code (UBC-97). Each building code has formulated design spectrum, like, Euro code (EC08), International Building Code (IBC-03) and UBC-97. Since, BCP-07 follows UBC-97 design
response spectrum (DRS), it is questinable that whether the UBC-97 DRS considers the zone
characteristics of Pakistan. Response spectra are very useful tools and the DRS depends upon many
factors including the magnitude of the earthquake, the fault mechanism and the distance of the site
from the fault, the geology of the travel path of seismic waves and the local soil conditions at the site.
Therefore, for the DRS seismicity of the area need to be considered. With the limited available data it
is realized here that the design, based on UBC-97 DRS with site specific seismic coefficient, is safe.
However, with the scaled up records according to the PGA maps of BCP-07, UBC-97 DRS is less
conservative for rocky soil (high seismic risk zone 4). Considering stiff soil strata (Soil type D Zone
2A), peaks for UBC-97 and proposed spectra almost coincide with each other.