Ultimate Capacity Of Steel Tubular T-joints With Concrete-Filled Chord Member After Fire Exposure

The steel tubular joint has been widely used in offshore platforms,airports and large-span,due to their advantages of excellent mechanical properties,quick construction and have an attractive appearance.However,the steel tubular joint easily lose its bearing capacity under fire because steel material is very sensitive to high temperatures.If the concrete is filled in the chord of the steel tubular joint,the bearing capacity of joint post-fire and at ambient temperature can be advanced effectively.In the article,the bearing capacity difference of steel tubular T-joints with concrete-filled chord member after fire exposure that experience different peak temperature is focused.Three specimens with identical geometric properties were tested to failure:one specimen at ambient temperature and two after exposure to different high temperatures.The static test was carried out using an SDS500 electro-hydraulic servo universal testing machine The chord ends of each specimen were simply supported,and the load was applied vertically at the brace end.According to the experimental results,the strength of T-joints after exposure to target temperatures decreased with the increase of target temperature.Finite element package ABAQUS is used to simulate the test specimens and get the bearing capacity.The experimental results about the failure modes,the measured load-displacement curves and the ultimate capacity of the T-joints are found consistent with the finite element results,which validates the accuracy of FE model.In addtion,149 FE models were built in the subsequent detailed parametric analysis.The geometric parameters and material parameters including chord length/diameter ratio-?,diameter ratio-?,wall thickness ratio-?,chord diameter/thickness ratio-?,concrete-strength-fc,yield strength-f_y and fire temperature-T_max,are chosen.Finally,a parametric equation based on the parametric influence law is proposed.