Modeling the seismic response of a two-storey calcium silicate brick masonry structure with nonlinear pushover and time-history analyses

Abstract

In the recent years, increasing induced seismic activities have been observed in the northern part of the Netherlands due to gas extraction. These seismic events may cause severe damages to the building stock in this area, which is mainly composed of unreinforced masonry (URM) buildings not designed to withstand seismic loads. An extensive experimental campaign has been carried out at the Stevin II laboratory of Delft University of Technology to characterize the seismic responses of these URM structures. In this framework, a quasi-static cyclic pushover test on a full-scale masonry assemblage has been performed. In this treatise, the seismic behavior of the tested masonry assemblage is modeled and analyzed via finite element analyses. The validation against the experimental results is achieved through nonlinear pushover analyses on a well-built model of the assemblage. Moreover, as the pushover method used in the aforementioned studies is based on static loading, its accuracy and applicability on studying the seismic behavior for this type of masonry structure need to be evaluated. The evaluation is achieved by performing a series of nonlinear time-history analyses on the model to obtain accurate seismic response of the structure. The applied horizontal ground motion is representative of the earthquakes in the Groningen province and the incremental dynamic analysis method (IDA) is employed.
The nonlinear pushover analyses reproduce the test results properly, showing similar maximum base shear forces and asymmetric capacity curves. In both experimental and numerical analyses, cracks start to form at the top and bottom of the masonry piers due to rocking mechanism and the failure of the structure is governed by damages of the wide piers. Moreover, a sensitivity study based on the monotonic pushover analysis shows that the post-peak behavior of the model is directly related to the masonry compressive strength. The incremental dynamic analysis provides similar base shear capacity and failure mechanisms as the nonlinear pushover analysis. However, the maximum displacement is smaller in both loading directions and a more distributed crack pattern is observed. Overall, for the studied masonry house, the pushover method is capable of properly estimating the base shear capacity but the deformation capacity might be overestimated.