UCLA

Fire spread simulation plays a significant role in mitigating the devastating impacts of fires in both wildland and urban areas. Over the years, the analogy of fire spread simulation has undergone a remarkable transformation from wildland area to urban area. Especially the structure damage assessment after the fire becomes more important these days. This research provides a fire spread model that is designed to simulate the affected area and assess the fire damage to concrete, steel, and wooden structures in both wildland and urban areas. There are three main parts in this research, the fire spread simulation, structure damage assessment, and the regional cost estimation.First, the fire spread simulation integrates Rothermel’s surface fire spread model, fire elliptical growth model, and Huygens’ principle. Rothermel’s surface fire spread model takes into account factors such as weather conditions, terrain, and fuel types to predict the fire spread rate. The elliptical growth model combines not only a mathematical approach but also empirical results that come from past research. Finally, Huygens' Principle of Fire Front Expansion is a pivotal concept in fire growth modeling, particularly in sophisticated vector or wave-type models. In addition, this model accounts for the impact of firebrands, which can lead to spot fires and are more commonly found in urban areas. Second, following the fire spread simulation, the nodes associated with a specific type of structure are equipped with time data that indicates the duration for which they have been exposed to the fire. Through the analysis of compartment time and temperature data, the temperature condition within the structure can be derived. Furthermore, a probabilistic model and the corresponding fragility curve have been developed to assist in the assessment of damage levels. Third, Monte Carlo simulation is adapted to account for the simplicity and uncertainty in environmental conditions while estimating the probabilistic economic losses within the affected area. This methodology aids in pinpointing areas of potential vulnerability and determining the likelihood of structure ignition. The assessment of economic loss consists of two parts, the damage to wildlands, and the damage to structures. The latter is further divided into the damage to structural and non-structural components. The aggregate repair costs for all nodes will represent the total economic loss in the area. In conclusion, this study developed a fire spread simulation model for the wildland-urban interface, incorporating inhomogeneous fuels and firebrand impacts, and created probabilistic models for structural loss assessment using fragility functions and Monte Carlo simulations. The model's accuracy and reliability were demonstrated through a case study, where the simulated fire spread and predicted regional losses closely matched real-world estimates. This model is essential for urban planners, civil engineers, and fire management professionals, providing a valuable tool to better predict, mitigate, and manage the adverse effects of fires.