Seismic Damage Analysis and Design of Unreinforced Masonry Buildings

Abstract

A model for evaluating the structural damage to masonry buildings subjected to earthquake ground motion is proposed. Damage is expressed as a combination of the effects of excessive deformation and repeated loadings. Model parameters for unreinforced brick masonry were obtained from cyclic load tests of masonry wall specimens. A random vibration method using a nonlinear hysteretic restoring force model to describe the load-deformation behavior of masonry was adopted to evaluate the response statistics required for damage assessment. The proposed damage model was calibrated using observed damages to masonry buildings during past earthquakes.

A simplified method for damage assessment, in which seismic damage is expressed as a ratio of the seismic loading to the structural resistance, is proposed. A damage-limiting design method, based on the equivalent lateral load procedure used in many building codes, is developed in which the base shear coefficient is expressed as a function of the damage level. Two design examples indicate the effectiveness of the design method to limit seismic damage to a tolerable level.