Experimental study of the fire resistance of inner rigid beam-column joints in steel frames

In order to study the fire-resistance of rigid joints in steel frames, four full-scale intermediate joints were tested and studied with 3D nonlinear finite element analysis software. In the experiment, the load value kept constant and only joints were exposed to fire to increase their temperature. The fire-resistance, critical temperature value and ultimate rotation of the joints were mainly investigated. The test results show that the fire-resistant time of rigid joints is short, being about twenty minutes in general. The column stiffeners can obviously improve both the critical temperature value and the ultimate rotation of the joints. The fire-resistance of welded connection is a little higher than that of bolted-and-welded joints, but there is no significant difference of ultimate rotation between them when failure occurs. The fire-resistance analysis of rigid joints was also made by employing the software package of ANSYS and the results agree well with the experimental ones. Suggestions on design and construction are also presented.