Post-fire Assessment Research Articles

A Local-Scale, Post-Fire Assessment in a Double-Burned Area: A Case Study from Peloponnisos, Greece

In the summer of 2021, Greece experienced significant forest fires and mega-fires across multiple regions, leading to human casualties and damage to the natural environment, infrastructure, livestock, and agriculture. The current study aims to assess the ecosystem condition in terms of the natural regeneration and soil conditions of an area burnt by a forest fire (2021), specifically in the Ancient Olympia region situated in West Peloponnese (Ilia Prefecture), Greece. A standardized field sampling methodology was applied to record natural regeneration at chosen sites where a forest fire had also previously occurred (in 2007), resulting in the natural re-growth of the Pinus halepensis forest. Furthermore, an analysis was conducted on the geochemical, mineralogical, and sedimentological properties of soils obtained from this location. The findings of the research demonstrate the decline in the established natural regeneration of the Pinus halepensis forest and the overall tree layer. Species characteristic of post-fire ecological succession were observed in the shrub and herb layers, displaying varying coverage. The examination of soil mineralogy, sedimentology, and geochemistry indicated that the soil characteristics in the area are conducive to either natural or artificial regeneration. Ultimately, recommendations for landscape rehabilitation strategies are provided to inform decision-making processes, considering future climate conditions.

A tuning-free moderate-scale burned area detection algorithm — a case study in chornobyl-contaminated region

ABSTRACT The predefined threshold is one of the main fundamental and methodological challenges underlying the uncertainty and delayed release of existing burned area (BA) products. To improve the accuracy and timeliness of BA mapping, a tuning-free moderate-scale BA detection algorithm (AT&RF algorithm) was proposed to carry out rapid BA mapping for the immediate post-fire assessment. A case study was carried out at the Chornobyl Exclusion Zone (ChEZ) to assess the performance of the algorithm. The evaluation results indicated that the algorithm successfully detected the BA in 2015 and 2020 in ChEZ, which outperforms the existing BA products by significantly decreasing the omission error by 18.6% and 15.1% and improving the Kappa coefficient and critical success index by 9.4% and 4.0% on average for MCD64A1 and FireCCI51 products, respectively. It is also possible to transfer the algorithm quickly to other regions without complicated adjustments and significantly improve the timeliness and accuracy compared to the existing global BA products for assessing environmental impact and scope.

Post-fire mechanical properties and constitutive model of Q690 high-strength structural steel

Fire hazard is one of the main threats to the integrity of steel structural buildings. Developing an accurate post-fire constitutive model for structural steel is crucial for enhancing the failure assessment of steel structures exposed to fire. In this study, the post-fire mechanical behavior of Q690 high-strength structural steel is investigated. Eighteen round bar specimens made of Q690 steel were heated with temperatures ranging from 20 °C to 900 °C. Tensile tests were conducted on these specimens to obtain the post-fire stress-strain curves and associated mechanical parameters of the material. To accurately characterize the post-fire behavior of Q690 steel, a temperature-dependent elastoplastic constitutive model combined with its numerical implementation algorithm is proposed. This model consists of four components: a temperature-dependent elasticity criterion, the von Mises yield criterion, an associated flow rule, and a temperature-dependent isotropic hardening law. The proposed constitutive model has a notable feature, i.e. the material parameters in the model can be defined as a function of temperature according to the test results. As a result, when utilizing this model for post-fire assessments of steel members, only three routine parameters, i.e. elastic modulus at room temperature, Poisson's ratio, and the temperature experienced by the material, are required in the numerical simulation to generate the material’s stress-strain relationships. To verify the proposed constitutive model, the new model was introduced into the numerical simulations of the tested round bar specimens after exposure to various temperature conditions. Both the load-displacement curves and local deformation of each round bar specimen obtained from the numerical simulations are compared with the test results to validate the accuracy of the new model. The constitutive model presented in this study provides a useful tool for assessing the post-fire behaviors of steel components.

Recent Advances in CFD-based Bridge Fire Evaluations: A Brief Review

Bridges, as the main elements of transportation networks, demand significant attention due to their unique structural characteristics and high consequences of fire incidents. So, it is crucial to enhance the fire resilience of these structures. Various studies have focused on the integration of advanced fire modeling techniques, including computational fluid dynamics (CFD), the finite element method (FEM), and artificial intelligence (AI) to improve the fire responses of the bridges. This article provided an overview of recent advancements in bridge fire modeling and addressing methodologies, challenges, and future directions for enhancing the fire resilience of bridge structures. Natural language processing (NLP) was employed for an in-depth exploration of bridge fire engineering topics and integrated CFD, FEM, and AI techniques. It has highlighted the importance of AI in enhancing real-time fire prediction and reducing related computational demands, emphasizing the importance of developing AI integrated approaches for the accelerated and effective post-fire assessment of bridge structures, considering their unique structural challenges and high impact of fires.

Incorporation of Indaziflam into Natural Areas Management of Cheatgrass and Other Short-Lived Invasive Species: Post-Fire Assessment in a Semi-Arid Colorado Grassland

Incorporation of Indaziflam into Natural Areas Management of Cheatgrass and Other Short-Lived Invasive Species: Post-Fire Assessment in a Semi-Arid Colorado Grassland

Post-fire assessment of composite steel-concrete box-girder bridges: Lessons from a recent incident

The structural fire analysis of bridges is crucial for ensuring transportation infrastructure safety since bridges, due to their unique characteristics and exposure to environmental hazards, are particularly susceptible to fire-induced damage. Despite this vulnerability, there is a lack of both experimental research and design guidelines for ensuring fire safety in bridges. This underscores the importance of studying actual bridge fire incidents.This article presents a comprehensive examination of the numerical and experimental investigations carried out to evaluate the structural condition of a composite box-girder bridge located in Valencia, Spain, following a significant fire incident. In addition, the paper details the repair works carried out to fully restore the operational capacity of the bridge, along with the key lessons learnt from the incident. Therefore, the article highlights the vital synergy between advanced numerical models and experimental investigations to strengthen rehabilitation action plans and gain valuable insights for making informed decisions regarding post-fire structural integrity. By doing so, the study enhances understanding of bridge safety under fire and provides actionable recommendations for researchers, practitioners, and transportation authorities.

Assessment of structures repeatedly exposed to thermal loading and extinguishing water: a case study of a firefighting training facility

When designing a new structure or assessing an existing one, the risk of fire and its effect on the structure must be considered. Structures are usually assessed for fire resistance at the design stage – i.e. before the possible exposure to fire. If structure is exposed to fire during its service life, a post-fire assessment must be conducted in order to evaluate whether the structure is still safe and reliable for use. The post-fire assessment is conducted quite regularly; however, the assessment is usually conducted for structures exposed to fire only once. This paper presents an interesting and unique case study of a post-fire structural analysis of a firefighting training facility exposed to cyclic fire loading and the effect of extinguishing water. The main conclusion of the study is that though means of protection are recommended, the structure still has a sufficient load-bearing capacity and can continue being used as a firefighting training facility in the future. Aside from the specific conclusions for the investigated structure, this paper presents the best practices and methods for the post-fire assessment of structures exposed to repeated fire loading, and can thus be used as a guidance by other engineers and researchers interested in this topic.

Post-fire assessment of recovery of montane forest composition and stand parameters using in situ measurements and remote sensing data

Tree diversity in the tropical forests face escalating threats from wildfires. This study assessed post-fire impacts and recovery patterns in Tanzanian Eastern Arc Mountains forests from 2017 to 2022 using field measurements and remote sensing techniques. Tree species diversity, composition, and forest stand parameters were compared between burned and unburned forest plots across two reserves. A predictive model utilizing 14 key variables derived from multispectral satellite data was developed to accurately map burned areas and spatial fire patterns. Results revealed significantly lower tree density, aboveground biomass, species richness, and Shannon diversity in burned areas compared to unburned forests. However, compositional analysis showed extensive species overlap between burned and unburned sites, with burned areas containing more indicative pioneer and disturbance-adapted species such as Apodytes dimidiata. Over time since fire events, tree density, basal area, aboveground biomass, species richness, evenness, and diversity increased markedly, evidencing active tree recovery. The remote sensing model effectively delineated approximately 1430 hectares of burned areas concentrated near villages, suggesting prevalent anthropogenic fire ignitions. Although wildfires substantially impacted forest structure and biodiversity, the limited compositional shifts point to resilience of these tropical montane forests. Integration of diverse spectral bands and textural metrics from multispectral satellite data can support precise mapping of fire effects and forest recovery dynamics in these ecologically vital yet threatened ecosystems, aiding conservation and management. Overall, this study provides novel insights into post-fire responses in Eastern Arc Mountain forests using a synergistic field and remote sensing approaches.

The power of eDNA sampling to investigate the impact of Australian mega-fires on platypus occupancy

Fire plays an important role in many ecosystems, but megafires are increasing the area burnt in forested regions globally. The 2019–2020 megafires in south-eastern Australia were unprecedented with respect to area burnt and the spatial extent of high-severity fire. Yet, there is limited knowledge regarding the impact of these megafires on biodiversity, especially aquatic fauna. Here we investigate the impact of the 2019–2020 megafires on the distribution of a semi-aquatic monotreme thought to be in decline: the platypus, Ornithorhynchus anatinus. We leveraged extensive pre-fire environmental DNA (eDNA) sampling and coupled this with additional sampling at two timepoints post-fire, to conduct a Before-After-Control-Impact (BACI) study. We used site occupancy-detection modelling to estimate platypus occupancy across fire affected and non-fire affected sites over time as well as the interaction between occupancy, high rainfall, and fire severity. We detected a negative effect of fire presence on platypus occupancy in both post-fire time periods. Platypus occupancy was also predicted to be lower at sites that experienced high rainfall post-fire and were situated within watersheds that had a large proportion burnt at high-severity. With area burnt and the extent of high-severity fire increasing globally, and predictions of more extreme rainfall events in south-eastern Australia in the future, the impact of fire on aquatic fauna requires greater consideration in post-fire assessments and biodiversity management more generally. The use of eDNA sampling and detection methods in a BACI framework provides a promising means to fill these knowledge gaps but does require pre-emptive sampling.

Post-fire assessment of heating temperatures experienced by concrete using short video imaging, hyperspectral imaging and laser-induced breakdown spectroscopy

This study develops rapid post-fire analysis methods to predict the heating temperature to which the concrete was exposed. Short video imaging (SVI), hyperspectral imaging (HSI) and laser-induced breakdown spectroscopy (LIBS) were used for the first time to obtain spectra of concrete after high-temperature exposure (100–800 °C). The differences in colour levels and spectroscopic signals due to varying temperatures were observed. To handle the complex relationship between spectra and temperatures, machine learning models were used to extract meaningful information from spectra for the quantification of temperature. Furthermore, domain knowledge related to concrete composition and LIBS signal was integrated into machine learning to improve quantification performance. The highest coefficients of determination for prediction achieved based on SVI, HSI and LIBS measurements were 91.4, 94.8 and 98.6, respectively. These results demonstrate that SVI, HSI and LIBS can be fast and viable methods for assessing the fire temperature that the concrete has experienced.

Application of a tuning-free burned area detection algorithm to the Chornobyl wildfires in 2022

The wildfires in the Chornobyl Exclusion Zone (ChEZ) have caused widespread public concern about the potential risk of radiation exposure from radionuclides resuspended and redistributed due to the fires in 2020. The wildfires were also confirmed in ChEZ in the spring of 2022, and its impact needed to be estimated accurately and rapidly. In this study, we developed a tuning-free burned area detection algorithm (TuFda) to perform rapid detection of burned areas for the purpose of immediate post-fire assessment. We applied TuFda to detect burned areas in the ChEZ during the spring of 2022. The size of the burned areas in February and March was estimated as 0.4 km2 and 70 km2, respectively. We also applied the algorithm to other areas outside the boundaries of the ChEZ and detected land surface changes totaling 553 km2 in northern Ukraine between February and March 2022. These changes may have occurred as a result of the Russian invasion. This study is the first to identify areas in northern Ukraine impacted by both wildfires and the Russian invasion of Ukraine in 2022. Our algorithm facilitates the rapid provision of accurate information on significant land surface changes whether caused by wildfires, military action, or any other factor.

A Theoretical Framework to Investigate Interdependency in the Assessment of Fire Resilience

Communities and ecosystems may be particularly vulnerable to fire hazard. In addition, modern societies are connected with interdependent infrastructures, and the assessment of their resilience to fire may be extremely challenging. In this regard, fire resilience may be described as the ability to maintain the functionality of infrastructures to deliver services during and after hazard events. This paper considers several typologies of interdependency in order to propose several models that may quantify fire resilience. These models are based on the previous literature and the applications recently proposed for earthquakes. Fire resilience is herein calculated by considering a multi-dimensional formulation of the repair function that depends on time and the different components of the systems. The formulations that are described may be applied for preliminary studies aimed at pre- and post-fire assessments. Many stakeholders may take advantages of such formulations to consider the interconnections between the different infrastructures, their components, and subcomponents subjected to fire hazard.

Towards a whole-system framework for wildfire monitoring using Earth observations.

Fire seasons have become increasingly variable and extreme due to changing climatological, ecological, and social conditions. Earth observation data are critical for monitoring fires and their impacts. Herein, we present a whole-system framework for identifying and synthesizing fire monitoring objectives and data needs throughout the life cycle of a fire event. The four stages of fire monitoring using Earth observation data include the following: (1) pre-fire vegetation inventories, (2) active-fire monitoring, (3) post-fire assessment, and (4) multi-scale synthesis. We identify the challenges and opportunities associated with current approaches to fire monitoring, highlighting four case studies from North American boreal, montane, and grassland ecosystems. While the case studies are localized to these ecosystems and regional contexts, they provide insights for others experiencing similar monitoring challenges worldwide. The field of remote sensing is experiencing a rapid proliferation of new data sources, providing observations that can inform all aspects of our fire monitoring framework; however, significant challenges for meeting fire monitoring objectives remain. We identify future opportunities for data sharing and rapid co-development of information products using cloud computing that benefits from open-access Earth observation and other geospatial data layers.

Post-Fire Assessment and Retrofitting of Concrete Buildings: Case Study

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Resistance and serviceability assessment of innovative composite slab exposed to standard compartment fire

The resistance and serviceability of an innovative flat profile steel–concrete composite slab fabricated with fire-resistant weathering (FRW) steel are investigated in depth. A total of five composite slabs are subject to full-process standard fire tests, with another five slabs for comparative tests under room temperature. The full-process fire tests include 60-minute heating, 180-minute forced cooling, 24-hour natural cooling test. The heating and cooling curves are recorded and simulated by a series of logarithmic functions. Based on the test results, an exponential model is proposed in terms of deflection rebounding ratio to evaluate the capability of self-restoration after fire exposure. The residual loading ratio is defined to describe and assess the robustness of the slab after fire. Analysis results show that this new type of composite slab exhibits very strong resilience and robustness after exposure to standard fire. Finally, based on sufficient standard fire tests and shear-bond tests, the specific post-fire serviceability performances are formulated, including flexural capacity, shear-bonding action, shear capacity, limiting deflection under normal service condition. The post-fire assessment method is further proposed, characterizing with resilience, robustness and reusability in terms of deformation restoration, residual loading capacity and serviceability both under normal service and fire resistance limit conditions, respectively. These research findings are of great significance in assessing the resistance and serviceability of horizontal separating elements after timely fire extinguishing, proper repairing and rehabilitation.

Post-fire seismic behaviour of a self-centring connection with buckling-restrained plates and pre-stressed bars

Fire hazard is regarded as a significant threat to structural systems, not only the resistance during the fire should be concerned but the post-fire assessment of structural performance is also of great importance. The post-fire seismic behaviour is the key metric for evaluating the residual performance of structures mainly serving seismic demands. However, limited research considers whether the self-centring system, one of the seismic-resilient structures, can still resist seismic loadings after fire exposure. Based on that, this study mainly aims to investigate the post-fire seismic response of a self-centring system with buckling-restrained plates and pre-stressed bars. A sequence of the fire exposure and the post-fire cyclic test was conducted on the cross-shaped specimen, and hysteretic behaviour after air-cooling was analysed and compared with the regular seismic response. Results showed that fire exposure not only significantly influences the geometric conditions of the self-centring system, but also completely transforms the original deformation mechanism. Pre-stressed bars were expanded and stretched during the fire so that could not provide self-centring capacity in post-fire conditions, while the energy dissipation of buckling-restrained plates was postponed and weakened because of the slippage at bolted connections. Compared with the regular seismic behaviour, the post-fire hysteretic response appeared sliding and pinching effect rather than the flag-shaped, with a much lower load-carrying capacity and extremely larger residual deformation. To improve the post-fire seismic resistance, the numerical model was established first to reappear the experimental response by the heat transfer analysis and post-fire static analysis, and then extended to simulate the post-fire repair in proposed strategies. According to the repair effect, it is suggested that the high-strength bolts should be replaced with pre-load, and the bars are required at least to provide additional stiffness and re-tensioned if necessary. The findings reveal the considerable influence of fire exposure on the seismic performance of the self-centring system, and highlight the importance of improving residual resistance of seismic-resilient structural systems in post-fire scenarios.

The Post-fire Assessment of Steel Structures, a Reliability-Based Semi-probabilistic Approach

The Post-fire Assessment of Steel Structures, a Reliability-Based Semi-probabilistic Approach

One year on: rapid assessment of fauna and red fox diet after the 2019–20 mega-fires in the Blue Mountains, New South Wales

ABSTRACT Australia’s 2019–20 mega-fires burnt 79% of the Greater Blue Mountains World Heritage Area, prompting an urgent need for rapid on-ground post-fire assessments of flora and fauna to aid in post-fire recovery. This project aimed to determine spatial patterns in populations and assemblages of vertebrates, vertebrate temporal activity, and the diet of the invasive Red Fox Vulpes vulpes, across burnt and unburnt sites. Using remote camera traps we surveyed 12 unburnt and 10 burnt sites approximately 12 months after the fires. We detected 41 species (11 mammals, 28 birds and 2 reptiles), with different species composition, but similar vertebrate species richness across both unburnt and burnt sites. The relative abundance of the Eastern Grey Kangaroo Macropus giganteus, Common Wombat Vombatus ursinus and Australian Magpie Gymnorhina tibicen was higher in burnt sites, while small mammals (< 500 g) had higher relative abundance at unburnt sites. There was no difference in the relative abundance of the Superb Lyrebird Menura novaehollandiae across burnt and unburnt sites, and although 11 species of bird were only detected at unburnt sites, the numbers were too low for reliable estimates of differences. Red Fox scat analysis (n=23) revealed that invertebrates and plant material were the dominant prey items in both burnt and unburnt sites, but medium-sized mammals increased in Red Fox diets in burnt sites, and reptiles were consumed disproportionately more by Red Foxes in burnt compared to unburnt sites. Although the short-term nature of this study and low scat sample size limited detailed insights, our rapid survey was an effective tool to gain preliminary data on species responses to the 2019–20 megafires in the Blue Mountains and contribute to a baseline for understanding species recovery.

Multitemporal dual-pol Sentinel-1 data to support monitoring of forest post-fire dynamics

Approaches based on multitemporal analysis of optical-retrieved vegetation index time series were successfully applied to describe forest disturbances like forest fires; conversely, only few works make use of multitemporal Synthetic Aperture Radar (SAR) data. In this work, a multi-temporal approach based on Sentinel-1 data (S1) is proposed based on CR polarimetric index to monitor forest canopy along the considered period (2016–2019) preceding and following an important fire event occurred in the Piemonte Region (NW Italy) in November 2017. The Pettitt test, applied to the polarimetric index time series, was used for testing fire occurrence date and map burned areas (795 ha) resulting in user’s accuracy of burned area equal to 88%. A trend analysis was also conducted, on ‘burned’ pixels only, to describe tree canopy damage and strength of the consequent recovery process at pixel level using linear trend slope values of cross ratio polarimetric index time series. Finally, a k-means cluster analysis was applied to define classes having the same ecological behaviour with respect to two different criteria: one aimed at mapping type and intensity of damage and a second one aimed at describing the ecological behaviour in terms of resistance and resilience of burned patches. In the study area, the cluster layer called forest damage map classifies about the 22% of burned area as characterized by an early high severity whiled the residual by moderate-low severity levels. The second cluster layer called ecological response map defined the 61% of the burned area as resistant forests, the 20% as resilient forests and the 19% as increasing forest zones. All maps were generated with the aim of supporting post-fire assessment and management with free satellite SAR data.

Post-fire mechanical behaviour of ultra-high-performance concrete-filled steel tube (UHPCFST) stub columns under compression

Twenty-four full-scale tests were carried out in order to investigate the post-fire behaviour of UHPCFST stub columns under axial compression after being exposed to elevated temperatures. The test parameters include cross-sectional size, heating mode, steel fibre content, and coarse aggregate content. The failure modes, cross-sectional historical maximum temperatures, axial load-deformation curves, and residual compressive capacities of the specimens are analysed. The test results revealed non-uniform and nonlinear distributions of the cross-sectional historical-max temperatures. It is found that the effect of historical temperature on the residual capacity of a UHPCFST column is more obvious with the increase of the heating rate and decrease of the cross-sectional size. Inspired by the concept of average temperature method under fire, a method for calculating the post-fire residual load capacity of CFST columns was proposed based on the average historical-max temperature of the cross-section. High accuracy has been found for using the proposed calculation method, therefore the work could serve as a reference for the post-fire assessment and strengthening of UHPCFST stub columns.