Estimation of failure probabilities of RC frame structures in Singapore to the simulated largest credible ground motion

Singapore is located about 400 km from the Sumatran fault and about 500 km from the Sumatran subduction zone in Indonesia. Although earthquake ground shaking has been felt occasionally, no damage to structures in Singapore has been directly attributed to Sumatran earthquakes. As such, building structures in Singapore are not designed to resist lateral earthquake loads, asides from a nominal lateral loading of 1.5% of the building weight as specified in BS8110 (British Standard Institution. BS8110: Structural use of concrete. Parts 1, 2, and 3; 1985). After the 1985 Mexico earthquake, the safety of the structures on soft soil sites in Singapore becomes a concern and lots of research effort has been spent on it. In this paper, the responses of three typical reinforced concrete (RC) structural models to a simulated earthquake event is assessed with consideration given to the statistical variation of the concrete and steel modulus and strength and dimensions of the structural members. A worst-case scenario simulated ground motion for Singapore soil sites is used for this analysis. The performance of the structures is assessed based on the resultant values of inter-storey drift. Probability and fuzzy set theory is used to estimate structural failure probabilities and to ad dress the ambiguity of the boundaries of the performance levels. Numerical results indicate that a typical RC low-rise structure is unlikely to be damaged, however medium-rise and high-rise structures are likely to be moderately damaged.