Seismic performance and fragility curves for reinforced concrete frame and shear wall residential buildings in Puerto Rico

Puerto Rico is situated in an earthquake prone region. Most of residential buildings in Puerto Rico are reinforced concrete structures. Because of the imminent risk of being affected by a strong earthquake, it is important to study their damage vulnerability. The lack of local earthquake vulnerability curves for Puerto Rico and the fact that local construction practice differs from that in USA motivates the author to look at the development of reliable fragility curves based on typical buildings properties and selection of ground motions based on local geology characteristics and past worldwide earthquakes scaled to different peak ground acceleration to obtain a wide range of maximum accelerations. This study is directed to low rise and medium rise concrete residential buildings in Puerto Rico. Typical lateral resisting systems, comprising moment frames and structural walls are considered. The analytical models are two-dimensional and are analyzed using the nonlinear dynamic time history method considering flexural nonlinear behavior for frames and both flexural and shear nonlinear behavior for shear walls. Algan's formulation (1982) and HAZUS drift limits were used to calculate the expected damage of the models. Damage to structures is quantified based on the inter-story drift ratio of the structure. The damage states considered were: Minor, Moderate, Substantial and Major, for Algan and Slight, Moderate, Extensive and Complete for HAZUS. With this information, lognormal functions expressed in the form of two parameters (log-median and log-standard deviation) were fitted and fragility curves developed as a function of PGA. It is common for concrete housing to have resisting elements oriented in only one direction. These structures are evaluated for forces in both directions independently and also taking in account both directions simultaneously. Multistory residential buildings in Puerto Rico commonly have shear walls oriented in both directions. A set of four fragility curves, one for each damage state is developed for each scenario studied. A total of 13 sets of fragility curves for each method are proposed. Multistory models proved to be the least vulnerable of the structures analyzed. These curves are useful tools for the insurance companies in Puerto Rico in order to improve their risk assessments.