Caternary Action Of The Restrained Castellated Steel Beams In A Fire

The catenary action of a restrained steel beam in a fire includes the contribution of the axial force to the bending moment bearing capacity of the beam. And the critical temperature of the beam could be increased. Compare with the solid steel beam, the castellated steel beam has the similar bending stiffness and a much lower axial stiffness, which leads to great difference to the catenary action of the restrained castellated steel beam in a fire.Based on the finite element approach, the catenary action of a restrained castellated beam with fillet corner opening in a fire is investigated. The expansion ratio, the height of the web opening, the shape of the web opening, the arrangement of opening and the beam span, the axial restraint stiffness ratio, the load ratio of the beam were chosen as the main parameters. The evolution of the axial force, the middle span deflection, the axial displacement and the middle span moment of the beam with the elevation of temperatures are presented. Comparing with the solid web beam, the castellated beam has a smaller compression force. The CSB goes into the catenary action at a lower temperature compared with the solid web one. The load ratio, the beam span and the axial restraint stiffness ratio were chosen as the main parameters to compare the castellated steel beam with the solid steel beam.The simplified hand calculation method can be used in catenary action of the restrained castellated steel beams in a fire. The main assumptions of the analytical model are the deflection profile and interaction between axial load and bending moment of the restrained beam in a fire. The proposed analysis will predict the axial force and the middle span deflection. This paper present validation studies of catenary action in restrained beams at largedeflections, by comparing the results of numerical simulations and the proposed method in this paper.