Experimental Study on the Behavior of Fire Resistance of Welded Hollow Spherical Joint under Compression

Through the transient test on two welded hollow spherical joints subjected to compression under fire, the temperature distribution, displacement characteristics, failure mode and ultimate fire resistance time of the joint under different load ratios were obtained under standard fire. The three-dimensional finite element model of welded hollow spherical joints was established, and the performance of the joints subjected to compression under fire was analyzed. Compared with the test results, the correctness of finite element simulation analysis was verified. The results showed that during the heating process, the surface temperature of the sphere inside the steel pipe is the lowest. The surface temperature of the sphere is low at the intersection with the steel tube and is highest at the middle-latitude of the sphere. The surface temperature of sphere is lower than ISO-834 standard heating curve. Failure mode of axially compressed welded hollow spherical joints under fire is concave failure. Failure position is at the sphere connected with the steel pipe. Failure process is short. Fire resistance time of load-ratio 0.35 specimen is more than 20% longer than that of load-ratio 0.6 specimen. The critical temperature of the current fire protection code is smaller than the results of the finite element.