Publication: Development of risk-targeted seismic design acceleration values for malaysian buildings
Date
2024-12-01
Authors
Ahmad Housam, Ramadan Arada
Journal Title
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Abstract
Several studies have illustrated that the seismic design employing the uniform
hazard concept does not ensure a uniform risk of collapse. Even in places with similar
Peak Ground Acceleration (PGA) values for the same return period (RP), seismic risk
might vary greatly, primarily due to differences in the shape of hazard curves and
uncertainty in structural capacity. Considering the worldwide tendency toward risk targeted (RT) seismic design maps, it is important to include Malaysia in this context
as well. Therefore, this study aims to apply the RT approach across Malaysia and
derive the risk-targeted design peak ground acceleration (PGAd
RT), for each location.
First, this study presents a representative exposure model for residential buildings on
Penang Island, Malaysia, which is the initial step in developing new risk maps. The
developed exposure model is predicated on a mini scheme derived from Global
Earthquake Model (GEM) Building Taxonomy. Second, an analytical-based approach
was introduced to derive the seismic overall fragility parameters, considering multiple
sources of uncertainty to ensure the proper development of comprehensive fragility
curves. The introduced approach uses the concept of the total variance and expectation
and weighing factors proportional to the probability of the presence of a certain
reference building (RB) with determined values in a particular region. The developed
building exposure model was utilized to evaluate the seismic overall fragility. IDA
was performed using eight far-field ground motions, yielding median inter-story drift
ratios (ISDR) and the IDA curves were plotted for three damage thresholds. The
introduced approach was performed based on the results obtained to compute the fragility parameters (particularly dispersion (β) and probability of collapse (X)) and
develop the fragility curves. The results were obtained in different forms from the
proposed procedure. Finally, given that the approach involves distinct input
parameters pertinent to the fragility curves, this study utilized the variability in the
input parameters previously illustrated. Thereafter, the produced fragility curves were
integrated with the existing hazard models for the region. Sensitivity analysis was
employed to investigate the impact of the variability in the input parameters and the
shape of the hazard curve on the PGAd
RT. The results were presented in tables
demonstrating the PGAd
RT levels at different targeted annual rate of collapse (λc)
values. They provide tailored design accelerations for various building types and
locations, ensuring a uniform risk of collapse across Malaysia. The derived PGAd
RT
levels were also compared with the current code provisions using risk coefficients
(CR). The findings indicated that employing the RT-design approach modifies the
current PGA values by either increasing or decreasing them based on the shape of the
hazard and fragility curves, and the λc adopted. Therefore, using proper hazard and
fragility curves representing the site and the structures leads to consistent results.