# Post-Earthquake Fire Resistance in Structures: A Review of Current Research and Future Directions
## 8 Performance-Based Design for PEF
### Performance Levels and Design Considerations  
Performance-based design for structures subjected to post-earthquake fire (PEF) considers both seismic and fire events, aiming to ensure adequate safety for occupants even under chaotic post-earthquake conditions [66]. Rather than addressing fire and seismic events in isolation, performance-based design integrates these requirements to achieve a predetermined performance level across various hazards [48]. Structures are typically designed to meet different performance levels such as Operational (O), Immediate Occupancy (IO), Life Safety (LS), and Collapse Prevention (CP), which correspond to increasing levels of damage, from minor (O) to severe (CP). For instance, at the LS level, buildings are designed to sustain significant damage to both structural and non-structural elements while ensuring the life safety of occupants by limiting drift values to around 2% [68]. The primary objective in fire design is to confine the fire within a compartment and prevent its spread. If containment fails, the design aims to ensure that the building remains stable long enough to allow for safe evacuation or fire suppression. Fire resistance, defined as the duration for which a structural member exposed to fire can maintain its integrity, is typically measured in minutes. Performance-based fire design considers various parameters such as compartment size, opening dimensions, and potential fire scenarios [66]. Performance-based PEF design must account for several critical factors:  
* Reduced Fire Resistance Due to Seismic Damage: Earthquake damage can significantly diminish a structure's fire resistance. For example, a reinforced concrete frame designed for LS performance exhibited a 400% reduction in fire resistance when subjected to fire following an earthquake, compared to its resistance in an undamaged state [68].
* Impact of Performance Levels on PEF Resistance: The seismic performance level for which a structure is designed influences its PEF resistance. Structures designed for higher seismic performance levels (e.g., IO) generally demonstrate better fire resistance post-earthquake than those designed for lower levels (e.g., LS) [68].
* Fire Scenarios: Different fire scenarios (e.g., fuel-controlled vs. ventilation-controlled) can significantly affect structural response. Employing natural fire curves, which consider factors such as ventilation and fire load, aligns more closely with the concept of performance-based design than standard time-temperature curve [66].
* Damage to Fire Protection Systems: Earthquakes can compromise fire protection systems such as sprinklers and fire-resistant coatings, thereby reducing their effectiveness during a PEF event [72].
* Impact of Connection Details: The performance of connections between structural members is crucial during both seismic and fire events. For instance, research on gusset plate moment connections indicated that connection rotation increased at temperatures above 400 \({}^{\circ}\)C, and the connection completely lost efficiency beyond 500 \({}^{\circ}\)C [98].  
The specific design considerations and performance levels will vary depending on factors such as:  
* Building Occupancy and Use: Different occupancies have varying safety requirements. For example, a school necessitates a higher performance level (e.g., IO) than a residential building (e.g., LS) due to the need for immediate evacuation following an earthquake [68].
* Building Height: Taller buildings are generally more susceptible to seismic forces and fire spread, requiring more stringent design considerations [63].
* Structural System: Various structural systems (e.g., moment-resisting frames, braced frames) exhibit different levels of performance under seismic and fire loads [48; 62].  
Further research is needed to develop comprehensive performance-based design guidelines for PEF that account for these complexities and offer reliable methods for predicting and mitigating the impact of this cascading hazard.