C. PRIYA (1), K. BALAJI RAO (1), M. B. ANOOP (1) and N. LAKSHMANAN (2)

(1) Scientist, Structural Engineering research Centre, CSIR Campus, Taramani, Chennai -113, INDIA

(2) Director, Structural Engineering research Centre, CSIR Campus, Taramani, Chennai -113, INDIA


The results of probabilistic failure analysis of single-storey and two-storey unreinforced brick masonry structures, typically representing those located in Bhadrachalam (in Andhra Pradesh) and in the Kanpur regions of India subjected to the excitation of Uttarkashi earthquake of 1991, are presented in this paper. The vulnerability functions are generated using a non-linear static approach and subjecting the structures to different levels of seismic excitation characterized by the spectral displacements. Both in-plane and out-of-plane behaviour of masonry walls are considered in the analysis. In order to take into account possible variations in the material properties of masonry, probabilistic vulnerability analysis is carried out using the well-accepted Monte Carlo simulation [20,28,31], treating compressive strength of brick, compressive strength of mortar, modulus of elasticity of masonry and angle of internal friction of masonry as random variables. Probabilistic vulnerability functions are generated for the structures and a fragility analysis is carried out to generate fragility curves for different damage grades defined according to the European Macroseismic Scale. The fragility curves are generated based on spectral displacements for each damage grade obtained from the probabilistic vulnerability function, and failure probabilities against each damage grade are computed. From the results of fragility analysis, it was found that failure probabilities at different damage grades for single-storey structure are less than those for two-storey structure and failure probability decreases with increase in compressive strength of brick. The usefulness of probabilistic failure analysis in performance-based design of structures is also discussed.