Nonlinear dynamic analysis of unreinforced masonry

A comprehensive analytical model has been developed and presented in this paper to study the response of unreinforced masonry to in-plane dynamic loads, including earthquake loads. The analysis has been implemented in a nonlinear finite element program. Masonry is treated as a nonlinear homogeneous orthotropic material. A failure envelope has also been developed that is capable of predicting both joint sliding and the cracking and/or crushing types of failure. The effect of bed joint orientation has been considered; this is achieved through a ubiquitous joint model. The model is capable of performing both static and time history analyses of masonry structures. Nonlinear dynamic analysis is carried out using the Modified Newton-Raphson iteration scheme in conjunction with the Newmark time integration algorithm. To calibrate the model and to demonstrate its applications, several numerical examples have been treated, and the results have been compared with those from full-scale tests on masonry shear walls under both cyclic and dynamic loads. Reasonably good agreement has been found between the analytical and experimental results.