Application of Multi-Directional Pushover Analysis to a Multi-Storey Structure Built of Tuff and Welded Tuff Masonry

The seismic assessment of masonry structures has been a major research topic. Although a variety of studies have been conducted, still further investigation is necessary to improve the accuracy of seismic assessment approaches. Earthquakes act on structures in two horizontal axes at the same time. To this am, multi-directional pushover analysis (MDPA) is considered effective to evaluate the behaviour of plan irregular structures under seismic loadings. The case study is a three-storey tuff masonry structure. It is positioned in Hokkaido, Japan. The façade is composed of welded tuff while the other walls are built of tuff. This case study shows irregularity in plan due to the use of different materials despite of simple geometry. A numerical model is prepared based on an in-situ microtremor test and laboratory material characterisation test. Nonlinear dynamic analysis (NDA) was also performed to compare results obtained from MDPA. NDA considered three accelerograms including one generated from the 2018 Iburi earthquake (6.6 Mw). It was one of the most intense earthquakes in Japan in the last 100 years. Comparison between NDA and MDPA examines the applicability of MDPA to plan-irregular masonry structures.