Computational modeling of structures subjected to extreme static and dynamic loads (such as snow, wind, impact, and earthquake) using finite-element software are part of mainstream structural engineering curricula in universities (at least at graduate level), and many experts can be found in industry who routinely undertake such analyses. However, only a handful or institutions around the world teach structural response to fire (at any level) and only a few of the top consulting engineers in the world truly specialize in this niche area. Among the reasons for this are the lack of cheap and easily accessible software to carry out such analyses and the highly tedious nature of modeling the full (often coupled) sequence of a realistic fire scenario, heat transfer to structure and structural response (currently impossible using a single software). The authors in this paper describe how finite-element software can be extended to include the modeling of structures under fire load. The added advantage of...

OpenSees is an open-source object-oriented software framework developed at UC Berekeley. The OpenSees framework has been recently extended to deal with structural behavior under fire conditions. This paper summaries the key work done for this extension and focuses on the application of the developed OpenSees to study the fire-induced progressive collapse mechanisms of steel structures. The implicit dynamic analysis method (Newmark method) is applied and the influences of the load ratios, beam sizes and fire scenarios on the collapse behavior of frames are investigated. Single-compartment fire scenarios in the central bay and edge bay are considered, respectively. A total of four collapse mechanisms of steel frames are proposed by varying the three influencing factors. Most of the collapse of steel frames is triggered by the buckling of the heated columns. The thermal expansion of heated beams at early heating stage and their catenary action at high temperature have great influences on the collapse mechanisms. The most common collapse mode of steel frames are in the form of lateral drift of frames above the heated floor together with downward collapse of frames along the heated bay. As the load increases, the collapse behavior of structures is dominated by a downward collapse of the whole frame with little sign of the upper frame drift. The collapse modes of steel frames with strong and weak beams are column failure mechanism and beam failure mechanism, respectively. The former mechanism is due to the buckling of the columns below the heated floor represented by a global collapse of the frame and the latter is initiated by the premature development of plastic hinges at the ends of beams denoted by an obvious lateral drift of the heated floor. Generally, the edge bay fire is more prone to induce the collapse of structures than the central bay fire. It is found that the most dangerous situation is the frame subjected to high load ratios exposed to a central bay fire where its progressive collapse may occur as early as 250°C.

High-strength structural steel of nominal yield strength greater than 690 MPa is difficult to produce in the hot-rolled condition without heat treatment. Quenching and tempering are thus commonly used to trade ductility for high strength. However, in seismic regions, good ductility of steel structural members is required to endure expected inelastic deformation under severe earthquake actions. This paper describes an experimental investigation on the mechanical properties and hysteretic behaviour of Q690D steel through 29 tensile coupon tests and 14 cyclic loading coupon tests subjected to four different cyclic patterns. The 16 mm and 40 mm quenched and tempered Q690D steel plates used in this study are equivalent to S690Q steel according to EN 10025-6. The test results of Q690D steel were compared with the ductility requirements of current seismic design codes. Under cyclic loading, Q690D steel showed cyclic softening. Based on analysis of the test results, a combined isotropic and kinematic hardening hysteretic model was developed to predict the cyclic behaviour of Q690D steel, with consideration of the Bauschinger effect and cyclic softening behaviour.

Fires are increasingly recognized as one of the major hazards causing damage to bridges and disruption in their operational continuity. As a transportation hub, cable-supported bridges are particularly critical to social sustainability and economic development. However, ensuring the resilience of cable-supported bridges in unexpected fire events has arisen as a challenge in recent years due to the lack of available standards and guidance for practitioners. In this context, this paper presents an up-to-date review of the fire resilience enhancement methods for cable-supported bridges and proposes research needs for impending decades. Representative fire incidents and the concerns of bridge managers are analyzed to define the critical fire scenarios that need to be considered in future fire-resistant designs. The fire performance of cable-supported bridges whose cables, girders, and pylons are exposed to fires are analyzed respectively. To enhance the fire resilience of cable-supported bridges, this paper compiles probabilistic methods, including fire risk evaluation and mitigation based on identified vulnerable bridges, and deterministic methods, including active and passive fire protection measures. This paper reveals that guidance on the fire resilience of cable-supported bridges should be further improved with regard to aspects including the fire performance of cable systems, the ability of cable-supported bridges to provide continued service in fires, risk- and cost–benefit-based fire resistance design, multi-level fire damage determination, and emergency response strategies.