# Post-Earthquake Fire Resistance in Structures: A Review of Current Research and Future Directions
## 5 Methodology
### Software and Computational Tools  
Various computational tools are utilized to conduct PEF analyses efficiently:  
* SAFIR--Finite element software for thermal-structural fire analysis [55];
* OpenSees--Open-source platform for seismic and fire-following-earthquake (FFE) simulations [56];* Ozone--A zone model software for predicting fire development and smoke propagation [57];
* MATLAB--Utilized for heat transfer modeling and custom computational scripting [58];
* ABAQUS--Advanced finite element analysis (FEA) software for coupled fire-seismic response studies [59];
* SAP2000--Commonly used for pushover analysis and seismic performance evaluation [60]. Each of these dimensions is integral to the comprehensive assessment of a building's PEF resistance, underscoring the need for a multi-faceted approach to ensure structural safety and resilience in the face of compounded hazards. Simulating seismic damage in reinforced concrete (RC) elements often involves modifying numerical models to reflect the expected degradation. One common approach is the reduction of concrete cover in plastic hinge regions, where damage concentrates during seismic events [1]. This reduction simulates cracking and spalling, with varying degrees of removal representing different damage levels [51; 52]. Minor damage (D0/D1), characterized by minimal cracking, assumes an intact section with negligible impact on thermal properties, aligning with the Immediate Occupancy (IO) performance level [51; 52]. Slight damage (D2), typically simulated by removing 50% of the concrete cover, represents spalling and exposure of reinforcement, corresponding to the Life Safety (LS) performance level [51; 52]. Severe damage (D3) involves complete removal of the cover, exposing the reinforcement and reflecting the Collapse Prevention (CP) performance level [51; 52]. To streamline complex post-earthquake fire (PEF) analyses, simplified criteria are employed to represent these damage levels [51]. Additionally, some studies utilize geometric damage parameters, such as relative crack depth and spalling extent, to quantify damage and its influence on the thermal behavior of RC elements [61]. In steel structures, earthquake-induced damage to components can be modeled as a combination of geometric damage and mechanical damage, such as residual deformation, including stiffness and strength degradation. For example, in one study, the inter-story drift angle was used as the primary indicator of structural damage, with residual values of the inter-story drift angles representing the seismic damage in a structure with non-degrading components [62].Another study introduced a comprehensive damage index (damage variable) to quantify the extent of damage in welded-bolted hybrid connection joints under seismic loading [63]. Researchers have also utilized the Johnson-Cook ductile damage model to capture the degradation of steel elements in damage models [36]. This model defines the damage initiation point as the equivalent plastic strain (\(\epsilon_{d}\)), which is a function of stress triaxiality (\(\sigma^{*}\)), strain rate (\(\epsilon\)), and homologous temperature (\(T^{*}\)):  
\[\epsilon_{d}=D1+D2\exp(D3\sigma^{*})(1+D4\ln(\dot{\epsilon}))(1+D5T^{*}) \tag{1}\]  
The five constants D1-D5 are specified in Johnson and Cook [64]. The model assumes that the damage variable evolves linearly, allowing the equivalent plastic displacement to be defined at the point of full material degradation (\(\epsilon_{f}\)). Some studies note that damage to non-structural elements, such as walls, partitions, and external glazing, can significantly impact a building's fire performance [65]. For example, damage to non-structural fire protection systems can accelerate fire spread and lead to quicker temperature increases in structural elements. Another reference describes tests conducted to evaluate the performance of fire door sets after simulated earthquake damage.