Seismic behavior of hinged steel frames with masonry infill walls

Abstract

Historic buildings are important parts of our cultural heritage and contribute to the social and economic of communities. Hinged steel frames with masonry infill walls were extensively used in conserved historical buildings built in the early 20th century in Shanghai, China. Those historical buildings are characterized by low strength in materials and the seismic actions were not properly considered in designs. Therefore, a better insight into their seismic performance assessment is necessary for both structural rehabilitation and maintenance of historic architectural features. This paper describes an experimental and numerical investigation on seismic behavior of hinged steel frames, with a special focus on the effect of masonry infill walls. Shaking table tests were conducted on two 1:4 scaled three-story, two-bay hinged steel frame model structures, i.e., a bare steel frame (Model M1) and a steel frame with masonry infill walls (Model M2). Three seismic records, i.e., Shanghai artificial signal (SHW-II, which was specified for the type IV soft base conditions in Shanghai), El Centro signal (obtained from the Imperial Valley earthquake in 1940) and Pasadena signal (obtained from the Kern County earthquake in 1952) were selected. The failure modes, dynamic characteristics, acceleration, inter-story shear forces as well as inter-story drifts of the two model structures were measured and compared. Three-dimensional finite element (FE) models of hinged steel frames with and without masonry infill walls were established. Effects of the stiffness of beam-column joints and the distribution of infill walls were also investigated. Results indicated that masonry infill walls altered the distribution of lateral force and increased the stiffness of the frame, leading to a noticeable reduction of structural deformation. The effect of infill walls was related to the ratio of stiffness of the walls to that of surrounding frames. In addition, a soft-story mechanism could occur in the case of partially infilled frames.