Towards the use of time-history analysis for the seismic assessment of masonry structures

Abstract

Despite being recognized as the most accurate analysis technique for the design and assessment of masonry structures, nonlinear dynamic analysis is not commonly used in the everyday engineering practice. Reasons for this can be found in the difficulties in the selection of appropriate input ground motion records, in the limited availability of computer programs allowing the performance of time history analysis, especially for the case of masonry structures, and in the issues related with interpretation of the results in terms of performance limits. Real records are well known to be a preferable choice with respect to artificial or synthetic ground motions, but the limited availability of real records often requires scaling them, with all the concerns associated with this operation. Also, a proper selection of seismic input requires some level of expertise, which is not so common in the professional field. Regarding numerical modelling of masonry buildings, an analysis tool capable of reproducing both global seismic response and local mechanisms would be the preferable option. Existing equivalent frame models including suitable nonlinear macro-elements representative of the behaviour of structural members allow performing time-history analyses of the global response of complete 3D building models. A modified macro-element model accounting for second order effects can be suitably adopted for the analysis of local failure modes, which are mainly associated with bending-rocking behaviour and out-of-plane wall response.