Inelastic analysis of semi-rigid composite structures under fire conditions

this paper presents the application of a proposed numerical approach, denoted as saafe program (system for advanced analysis for fire engineering), developed to provide an inelastic analysis of steel and composite (steel-concrete) 2d semi-rigid framed-structures under fire conditions. the proposed structural model allows an accurate description of the structural non-linear response, with less computational effort when compared to the general fem formulation. the method, although similar in concept to earlier plastic-hinge approaches, differs with regards to numerical implementation methodology and precision. the proposed plastic-hinge model is formulated in a succinct format based on the following characteristics: (i) a refined plastic lumped formulation with interaction surfaces, (ii) a tangent modulus model which includes both gradual inelastic loss of stiffness and ultimate strength of column members, (iii) a second-order large-displacement formulation, based on the stability functions concept, (iv) non-homogeneous temperature distribution over the cross-section, (v) a connection semi-rigid model. obtained results for connection model calibration examples are compared to reported experimental data, showing reasonable agreement. in addition, results of a proposed case-of-study demonstrate the efficiency and robustness of the saafe model to perform inelastic analysis semi-rigid members, outlining the advantage of considering advanced analysis in the current fire-design practice of structures.