Dynamic and cyclic response of a full-scale 2-storey cold-formed steel structure with and without infill materials

Cold-Formed Steel (CFS) has become more and more popular in recent years as an alternative construction material. Short construction time and very high strength to weight ratio under lateral forces made cold-formed steel an attractive option in earthquake prone countries such as Japan, New Zealand and the US. These structures are formed of CFS frames with either boards and sheatings attached to the frames or infill materials sprayed to the frames on-site. This paper presents the results of dynamic and cyclic experiments conducted on two different 3-D and 2-storey models. The first model was CFS frame system without infill material and the second one was with infill material. In order to identify the actual dynamic characteristics of models such as modal frequencies and damping ratios, large-scale tests are conducted instead of 2-D panel tests. Ambient vibration tests were carried out to determine modal frequencies of the models at different damage states and forced vibration tests were carried out to determine modal damping ratios at high vibration levels. In addition to ambient and forced vibration tests, cyclic tests were performed to obtain the hysteretic behavior of the model. It was observed that with the application of infill material, lateral load resisting capacity increased by 3.5 times, ductility of the model increased from 2.58 to 3.96 and damping ratio increased from 6.7 to 9.0%. In addition to identification of dynamic characteristics, the main motivation of this study is to investigate the possible use of ambient vibration surveys in the determination of damage level. Results showed that ambient vibration surveys can be used as a damage detection tool after an earthquake or any other hazard.