Seismic risk mitigation of concrete-filled double-skin steel tube frames with beam-only-connected shear walls

This paper proposes beam-only connected steel plate shear walls (BSWs) and composite shear walls (BCWs) to mitigate the seismic risk of concrete-filled double-steel tube (CFDST) frames. As a new type of structural system, limited works have been reported on the performance limit definitions and risk-informed assessment of them due to the lack of experimental and analytical data. According to the cyclic tests results performed by the authors and the guidance of FEMA 356, three stage of limit states are defined and the corresponding results are recommended. Then, an elaborate numerical model is developed that considering the nonlinear behaviour of materials, panel zone, beam-column joints and shear walls, and the model is validated by the test results. Besides, three CFDST buildings with different height and two CFDST buildings with BSW or BCW are modeled based on the validated numerical model. Finally, seismic fragility analyses as well as seismic risk assessments are conducted on these models, and the annual occurrence probability and collapse probability of the structure within 50 years are calculated. The results show that both BSWs and BCWs can effectively mitigate the seismic responses and risks of CFDST buildings, and the collapse probability of buildings within 50 years decreases from 7.7 % to 1.39 % and 1.24 % due to the equipped BSWs and BCWs, respectively.