Research On Failure Mechanism And Ultimate Strength Of Internally Ring-stiffened Circular Hollow Section Tubular Joints At Elevated Temperatures

Circular hollow section(CHS) steel tubular joints are widely used in steel tubular structures due to their excellent mechanical performance and aesthetic appearing. CHS tubular joint failure often occurs on chord surface in the vicinity of brace-chord intersection because the chord radial stiffness is relatively lower than brace axial stiffness. Internal ring stiffeners are commonly used to enhance the chord stiffness. There are many advantages of internally ring-stiffened CHS tubular joints, including large ultimate strength and high stiffness.Up to now, most research on internally ring-stiffened CHS tubular joints has been focused on the mechanical performance of the stiffened joints at ambient temperature. Based on the failure mechanism of the stiffened tubular joints, design equations for predicting the stiffened joint strengths were proposed in existing literatures. As the mechanical properties of steel materials deteriorate drastically with increasing temperature, steel tubular joints may fail at a load substantially lower than the failure load at room temperature. The joint failure could result in the collapse of entire steel tubular structures. Therefore it is necessary to conduct related studies on the mechanical performance of internally ring-stiffened CHS tubular joints in fire.Using ABAQUS, the failure mechanism and ultimate strengths of CHS steel tubular DT-, T- and Y-joints subjected to brace axial compression or tension were investigated in this paper. Details of the research conducted in this paper are as follows:1) The failure mechanism of the stiffened DT-, T- and Y-joints with different joint geometric parameters, stiffening positions, brace loading directions and joint temperatures was investigated.2) The effects of joint geometric parameters, stiffening positions and brace loading directions on the stiffened DT-, T- and Y-joints strength reduction at elevated temperatures were studied.3) The strengths of the stiffened DT-, T- and Y-joints with different joint geometric parameters, stiffening positions, brace loading directions and joint temperatures were numerically analyzed. Design equations for the stiffened joint strength predictions were proposed by introducing a temperature factor.