C. Yang - Senior Engineer, China Northwest Building Design Institute, Xi’an, P.R.China,

While a lot of unreinforced masonry buildings collapsed, several multistory buildings in confined masonry damaged slightly in the past earthquakes in China. Based on the results of additional model experiments, the confined masonry and concentrated reinforced masonry structures have been widely applied to the low-rise and medium-rise buildings respectively in the seismic zone. For the low-rise buildings the reinforced concrete ring beams are placed at each floor and the post-cast tie columns are placed at each intersections of interior and exterior masonry walls. For the medium-rise buildings in addition to the ring beams and tie columns, the post-cast reinforced concrete intermediate columns and horizontal belts are placed in all the masonry walls at spacing of 2~3m and 1~1.5m respectively. Model experiments and engineering practices show that the concentrated masonry structures have a good strength, deformability, seismic reliability and can be applied to the multistory buildings up to 10 stories in the seismic zones