Seismic behaviour of a new type of external hoop assembled joint for RC Frame- added layer hybrid structure

Abstract

The connection between upper and lower structures is the key to the seismic design of reinforced concrete frame-added layer hybrid structure. A new type of external hoop assemble joint for this hybrid structure was proposed in this study. This joint was used to strengthen the connection between existing and new structures, reduce the stiffness mutation, and enhance the overall cooperative seismic capacity of a structure. The experimental and finite element analysis results of four specimens with different upper column section types and joint types under reversed cyclic loading were discussed in terms of failure phenomena, failure modes, process of angle change of beam and column, strength degradation, stiffness degradation, hysteretic curves, skeleton curves and energy dissipation capabilities to study the seismic performance of this new type of joint. Results indicate that the plastic hinges of the new type of external hoop assemble joints are moved outwards to the edge of the external hoop steel plate of column foot. The damage position is moved away from the interface between the column and the beam, thereby protecting the core area of joint effectively. The new type external hoop joint has a fuller hysteretic curve, higher load-bearing capacity and slower strength and stiffness degradation than the traditional exposed rigid joint. Specimens with box-shaped cross section upper steel column have better energy consuming ability than specimens with I-shaped cross section upper steel column. The section form and stiffness of the upper steel column has a greater influence on the seismic performance of the hybrid joint. Reasonable suggestions are provided. This study can provide scientific basis and technical support for light steel hybrid structures.