A mathematical model for the in-plane non-linear earthquake behaviour of unreinforced masonry walls. Part 1: Experiments and proposed model

In this study a mathematical model is proposed to predict the non-linear in-plane behaviour of clay brick masonry walls when subjected to dynamic excitations. Owing to its length, the study is divided into two parts. This part is devoted to a description of the appropriate experiments and to the development of the mathematical model, including use of experimental data. In Part 2 the model is completed by establishing the parameter functions appearing in it. The form of the non-linear model is established by developing a simple, linear model from more complicated ones previously developed by the authors, and then extending this simple model to cover behaviour in the non-linear range. The model contains two types of parameter function. One describes elasto-plastic stresses and depends on strains; the other describes viscous stresses and is a function of strain rates. The experimental work was carried out using the shaking table of the Earthquake Engineering Research Center, University of California, Berkeley. The experiments involved in-plane horizontal earthquake excitations. The intensity of excitation, starting with a small value, was increased gradually through the beginning of cracking until damage was complete. Time histories of accelerations and displacements relative to a fixed frame were recorded at the upper and lower edges, and at the mid-height of the wall specimen. At the end of this part, the experimental data are processed to obtain the data for a ‘complex frequency response function’ of the wall specimen. The reduced data will be used in the optimization analysis in Part 2. Copyright © 1989 John Wiley & Sons, Lt