Displacement-Based Earthquake Loss Assessment of Adobe Buildings of Pakistan

Abstract

The calibration of a nonlinear static displacement-based method is carried out for seismic vulnerability assessment and earthquake loss estimation of adobe buildings in Pakistan. The method makes use of equivalent static single degree of freedom (SDOF) systems, completely defined by secant vibration period, limit state displacement capacity and viscous damping, to assess the seismic vulnerability of structures with due consideration of expected uncertainties in geometrical and mechanical properties of the structures besides the uncertainties in seismic demand. Nonlinear time history analyses (NLTHA) of twenty one case study buildings, with geometric and material uncertainties, are performed in order to derive mechanical model of adobe buildings for global mechanism. Furthermore, available recommendations for other types of masonry are employed to derive the local out-of-plane mechanical model for adobe buildings using static analysis. The mechanical models are used to derive fragility functions for adobe buildings which can be used to predict the socio-economic impacts of earthquakes for future preparedness and risk mitigation in the region. Comparison of the analytical prediction is carried out with the observed vulnerability in 2008 Balochistan earthquake which is found reasonably accurate in estimating the mean damage ratio at the site for the considered earthquake.