Seismic performance of curved haunched connections in modularized prefabricated steel structures

Abstract

In this study, curved haunched connections were developed for modularized prefabricated steel structures, where prefabricated steel pipe columns with curved haunches and H-beams are assembled on-site with connectors and bolts. The seismic performance of the developed connections was investigated, based on a cyclic testing and finite element analysis of two full-scale specimens. Critical seismic performance measures associated with the joints, such as the failure pattern, hysteresis property, stiffness degradation, ductility, and initial rotational stiffness, were analyzed; furthermore, the effectiveness of the different curved haunches in enhancing the seismic performance of the joints was discussed. A comparative analysis based on experimental and numerical tests revealed that the curved haunches could increase the flexural resistance of the steel pipe columns, change the internal stress distribution of the steel H-beams, and enhance the rotational stiffness of the joint. Owing to the existence of the curved haunches, the beam flanges around the haunch ends fail prior to the damage of the H-beam ends. Connections with shorter haunches are more prone to yielding, owing to the shorter legs of the haunches causing greater stress concentrations in the beam flanges around the haunch ends. In addition, the ductility of the connections crucially hinges on the beam flanges around the haunch ends, where proper strengthening is required to diminish the stress concentrations and section weakening caused by the bolt holes. Both connections can be classified as rigid, and the initial rotational stiffness is related to the length of the curved haunch. This study also presents a theoretical calculation method for the elastic panel zone rotational stiffness.