A Practical Approach for Fire Resistance Design of Restrained High-Strength Q690 Steel Beam Considering Creep Effect

Most of the previous studies on restrained steel beam behaviour in fire conditions have neglected the creep effect due to the lack of applicable creep models. A finite element model (FEM) is determined in this study to investigate fire resistance and the behaviour of restrained high-strength (RHS) Q690 steel beams in fire considering the high-temperature Fields & Fields creep model. A comparison of the results obtained by the FEM with those from previous tests proved the validity of the FEM. A second FEM without a creep model is also established to study the influence of creep on the fire resistance of restrained steel beams. Results showed that creep has a serious effect on the behaviour of restrained steel beams in fire. Thus, ignoring creep will possibly lead to unsafe designs. Several parametric studies are carried out using the validated FEM with the aim to investigate the influencing factors on the fire response of RHS Q690 steel beams. Analysis shows that some of the investigated factors, such as heating rate, cross-section temperature distribution, rotational restraint stiffness and span-to-depth ratio, have been found crucial in the fire resistance of RHS Q690 steel beams. Furthermore, a simplified approach is presented for RHS Q690 steel beams based on the results of the FEM, including the creep effect, to calculate the moment capacity. This approach is also suitable for calculating the critical temperature of RHS Q690 steel beams.