Abstract
This paper presents a new empirical-based model for nonlinear modelling of a steel beam using the concentrated hinge approach for the progressive collapse assessment. The new empirical-based model defines the momentrotation response of a steel beam considering the development of tensile catenary action. In the ASCE41-17, the nonlinear behaviour defining the backbone curve was derived purely based on the flexural behaviour of the structural member under cyclic loading without integrating the effect of high tensile catenary action build-up. Therefore, the backbone curve can further be improved. A comprehensive parametric study was first carried out to investigate the effect of the tensile catenary action on the flexural resistance of the beam under various structural parameters using ABAQUS software. Four variables were examined, which includes the span length, section size, material strength and ductility. A new empirical moment-rotation model was then derived based on the data obtained from the parametric study. A detailed comparison was made between the generated output results of the moment-rotation response predicted by the ASCE41-17 backbone curve and the new empirical moment-rotation model proposed in this paper. The moment-rotation response results generated by the ASCE41-17 model illustrates that the model tends to overestimate the ultimate chord rotation (theta u) of the beam member as the beam slenderness ratio (L/D) approaches 20. Meanwhile, the new empirical model consistently predicts the flexural behaviour of the beam up to ultimate moment resistance.