Bearing Capacity of Composite Joints of U-shaped Steel Composite Beams and Concrete-filled Square Steel Tubular Columns Based on Channel Steel Connection

Abstract

Traditional beam-column connection structures fail to meet design requirements of hidden beams and columns in the application of composite frames formed by U-shaped steel composite beams (USCBs) and concrete-filled square steel tubular columns (CFSTBCs) to residential buildings. Therefore, a novel beam-column connection structure of U-shaped steel composite beams and concrete-filled steel tubular columns based on channel steel connections was proposed in this study. An experimental study and finite element simulation analysis of the joint performance of the novel composite frame side joint specimen under monotonic load were carried out. Failure mode and bearing capacity of joints under negative bending moment were discussed based on the experimental investigation of two full-scale joints. The influence of beam section height, width-thickness ratio of column, and axial compression ratio on the bearing capacity of joints was explored by analyzing parameters of the finite element model. Results demonstrate that failure form of the joint is tensile crack of concrete floor at flange of core area of the joint under the action of negative bending moment, ductility coefficient of the joint is greater than 2.0, and bearing and ductility performance is excellent. Beam section height significantly influences the bearing capacity of joints, while the width-thickness ratio of the steel tube column slightly influences the bearing capacity of joints when the requirement of “strong columns and weak beams” is met. The bearing capacity of the joint is minimally affected by the change of axial compression ratio when the axial compression ratio of the column is less than or equal to 0.6. However, the bearing capacity is significantly reduced with the increase of the axial compression ratio when the axial compression ratio is greater than 0.6. This study can provide a theoretical basis for the engineering application and popularization of the novel composite frame beam-column connection structure.