Research On The Seismic Performance Of Gusset Plate Connection In Special Concentrically Braced Frames

Gusset plate as a common element is used to connect the brace and frame in concentrically braced frame(CBF).Its performance will affect the seismic performance of the concentrically braced frame.Brittle failure of gusset plate will result in the loss of strength and stiffness of CBFs and brittle failure of braced frame.In the paper,the seismic behavior of the gusset connection in the CBF is studied by experiments and finite element analysis.The force mechanism of the gusset plate,design method and simplified model are proposed.Based on experiments of the three-story CBF of the University of Washington,elastoplastic analysis and incremental dynamic analysis of this braced frame are carried out.The results show that if the influence of the gusset plate is neglected during seismic analysis,the inter story drift ratio and residual deformation of the structure will increase.The seismic performance of the braced frame will decrease and collapse will occur easily.Therefore,it is recommended to consider the contribution of the gusset to the frame during seismic analysis and design.Taking the one-story CBF as research object,the parameters of details of beam-columnconnection are considered in the experimental study.The mechanism of gusset plate is deeply studied.The test results show that when the column section is box but the column stiffness is consistent,lateral stiffness of braced frame is similar.However,the column near the gusset have locally deformation.Therefore,it is recommended to use stiffeners inside the column when using the box column.When the beam-column joint is hinged and the column stiffness is reduced,the capacity of braced frame is reduced.The gusset plate is subjected to not only brace action but also frame action.The direction of brace action is along the brace axial direction.The direction of frame action is along the free tips of gusset plate.Based on the above experimental research,the mechanism of gusset plate in CBF is systematically studied.The simulation results verify that the action of gusset plate can be divided into two parts: brace action and frame action.When brace is in tension,the two actions work together.When brace is in compression,the gusset plate is only subjected to the brace action.According to the stress distribution and direction at the interface between the gusset plate and beam and column,a design method of gusset plate is proposed.The design method can consider both brace and frame actions.Based on the mechanism of gusset plate obtained by experimental study and finite element analysis,a simplified method is proposed during the overall analysis.This method directly considers the frame action of the gusset plate and can be based on the details of the beam-column connections,which provide design recommendations for the design of CBFs.