Civil and Architectural Engineering
Civil and Architecural Engineering
Department-College of Engineering-Sultan Qaboos University
Comparison Of Omani Seismic Code With International Counterparts
Hasan Abdul Saeed
Abstract
Seismic codes represent the guidelines on how simple buildings should be designed to ensure
that they can adequately resist seismic force during earthquake. Oman have been working
towards preparing its own seismic code for buildings. The code defines the Sultanate to have
two seismic zones (Zone 1 and Zone 2). This research focuses on the comparison of this Omani
Seismic code (OSC draft version) with International seismic codes (UBC97 and IBC2006) to
address the fundamental difference in terms of lateral forces distribution, maximum lateral
storey displacement, base shear and bending moments in structural components with three
building heights using three different analysis methods. The results have been compared on the
basis of international design practice and then based on seismic hazard level. From the design
perspective, Muscat which belongs to Zone-I according to OSC is defined as Zone-2A in UBC
and Zone-II in IBC, while from the seismic hazard perspective it actually is comparable with
Zone-1 and Zone-I of UBC and IBC respectively. For all the scenarios (building type and
analysis method) investigated, the UBC is found significantly more conservative than OSC &
IBC based on International design practice. The values of base shear obtained using UBC97
code are 40 to 70% higher and those from IBC are 30 to 65% more than the value obtained by
using the OSC for all buildings. The difference on base shear values between OSC and UBC &
IBC decreases as the building height increases. The UBC design response spectra have higher
spectral acceleration over the entire period range, and as a result, the response spectrum analysis
provides a much higher base shear, displacement and moment in the structural members as
compared to IBC and OSC. Similar results pattern is observed in dynamic analysis. Further,
comparison between the codes based on seismic hazard, the OSC is found slightly more than
UBC & IBC. Finally, a brief comparison is made to do the cost benefit analysis for mostly
constructed low rise building under seismic and without seismic design using UBC and OSC
code. It is found that the strength and stiffness requirements for OSC is much lower compared
with UBC97 currently implemented design practice. Therefore, Omani Seismic Code is
preferable and more economical alternative for seismic design of low rise buildings in Oman.