Coupled thermo-mechanical damage modelling for structural steel in fire conditions

This paper aims at developing a coupled thermo-mechanical damage model for structural 6 steel at elevated temperatures. The need for adequate modelling of steel deterioration behaviour 7 remains a challenging task in structural fire engineering because of the complexity inherent in 8 the damage states of steel under combined actions of mechanical and fire loading. A fully three9 dimensional damage-coupled constitutive model is developed in this work based on the hypothesis 10 of effective stress space and isotropic damage theory. The new coupling model, adapted from 11 an enhanced Lemaitre’s ductile damage equation and taking into account temperature-dependent 12 thermal degradation, is a phenomenological approach where the underlying mechanisms that govern 13 the damage processes have been retained. The proposed damage model comprises a limited number 14 of parameters that could be identified using unloading slopes of stress-strain relationships through 15 tensile coupon tests. The proposed damage model is successfully implemented in the finite element 16 software ABAQUS and validated against a comprehensive range of experimental results. The 17 damage-affected structural response is accurately reproduced under various loading conditions and 18 a wide temperature range, demonstrating that the proposed damage model is a useful tool in giving a 19 realistic representation of steel deterioration behaviour for structural fire engineering applications

Fire fighting robot

Fire-fighting is an important but dangerous occupation. A fire-fighter must be able to put out fire quickly and safely. This is a common way to prevent fatalities and further damages. So, technology has done its part by bridging up the gap between fire fighters and machineries. So, a robot is invented in order to combine both man kind and technology [1]. Fire Fighting Robot is designed to put out a fire, before it reaches out of control. Robot with these fire-handling abilities is a great advantage to replace fire extinguishers [2]. Water-based robot will be an advantage for users to refill the tank as it goes empty. Users can fill up water and keep the robot in a safe position. Water is a basic non-chemical liquid which will not experience any expiry or damage or corrosion. This invention would be a great contribution to mankind in order to ease their work and minimize the risk during fire put out

An analysis of aircraft accidents involving fires

All U. S. Air Carrier accidents between 1963 and 1974 were studied to assess the extent of total personnel and aircraft damage which occurred in accidents and in accidents involving fire. Published accident reports and NTSB investigators' factual backup files were the primary sources of data. Although it was frequently not possible to assess the relative extent of fire-caused damage versus impact damage using the available data, the study established upper and lower bounds for deaths and damage due specifically to fire. In 12 years there were 122 accidents which involved airframe fires. Eighty-seven percent of the fires occurred after impact, and fuel leakage from ruptured tanks or severed lines was the most frequently cited cause. A cost analysis was performed for 300 serious accidents, including 92 serious accidents which involved fire. Personal injury costs were outside the scope of the cost analysis, but data on personnel injury judgements as well as settlements received from the CAB are included for reference

Assessment techniques for the evaluation of concrete structures after fire

As concrete structures exposed to fire behave in most cases very well, it could be of economic interest to repair the fire damaged structure. For this purpose a damage assessment based on scientific research is required as first step. In this paper, the Schmidt Rebound Hammer and colorimetry are addressed as toos for this assessment. Firstly, the effect of booth methods is studies on heated siliceous concrete specimens under laboratory conditions. Secondly, the practical applicability of both methods is examined by evaluating the fire damage of a concrete girder exposed to a real fire. Both techniques show to be very useful in evaluating the fire damage of the girder

Damage assessment of concrete structures exposed to fire

During a fire, concrete structures behave in most cases very well. It could therefore be of economic interest to repair the damaged structures, as costs for demolition and rebuilding can be avoided and the building can be reused faster. To assess the remaining loadbearing capacity in a scientific based way, information is necessary about the temperature distribution inside the concrete element and the residual material properties of both concrete and steel. But, at least of equal importance is a fundamental insight in how a concrete structure could behave during a heating cycle, as indirect actions due to thermal restraints can occur and cause significant cracking. These effects should be noticed during a visual inspection of the structure, however, cracks introduced by internal thermal restraints are not visible from the concrete surface. In this paper, fundamental knowledge is given about the effect of heating and cooling on the compressive strength of concrete. Diagnosis tools are discussed to obtain the temperature distribution, especially in the neighborhood of the reinforcement. Those techniques are based on the physico-chemical transformations of the cement matrix and the aggregates that occur during heating. To determine the effect of thermal restraints on the structural behavior, a methodology based on finite element methods is illustrated

3D finite element simulations of reinforced concrete elements exposed to fire

Fire could dramatically reduce strength of reinforced concrete elements and it is considered one of the major threats for the structural safety of buildings: structural members may even collapse due to intensity and duration of fire. In this study, 3D finite element simulations of reinforced concrete elements under fire loading are presented. A quasi static one-way-coupled thermo-mechanical analysis is carried out, in which a heat transfer simulation is conducted first and then internal forces are computed. A phe- nomenological constitutive model based on damage-plasticity is used for concrete at high temperature. Transient creep strains are included in the model for elevated temperature. Extended Leon model is used for yield function and isotropic damage is assumed. Numer- ical results are compared with experimental data found in the literature, showing good agreement

Impact of prescribed fire in soil properties after 5-years: experimental study.

Wildfires are a serious problem in areas with a Mediterranean climate owing to the hot summers and drought conditions providing perfect conditions for wildfire, especially when there are large amounts of fuel accumulation and continuity between forested areas. In the Mediterranean, high severity fires that spread rapidly are common and difficult to be extinguished. Thus, the identification of tools to reduce fire spread and minimize their incidence and effects is crucial. Preventive forestry is a good tool for achieving forest structures with lower amounts of fuel and a greater resistance to fire. Prescribed fire is the planned use of fire under predetermined weather, fuel and topographic parameters to achieve clearly defined objectives as controlling fire regimes by managing fuel, counteracting the disappearance of biomass-consuming land management practices and reducing the overall fire risk. Normally, prescribed fires are low intensity fires and, if managed adequately, do not cause any damage to trees, especially in Mediterranean ecosystems where trees are resilient to fire. Besides, prescribed fires usually have different impacts on soils, water resources, biodiversity, the risk-reduction of wildfires and carbon storage. Prescribed fires usually are of low/moderate severity. Because of this, the effects of prescribed fires on soils properties may vary from one site to another. The objectives of our study are to: i) determine the impact of the prescribed fire just after and ii) 5-years later with respect to natural conditions. To do this, in 2011, a prescribed fire was conducted in one experimental area of Mediterranean rangeland. After the fire, soil samples (0-5 cm of depth) were taken in burned and unburned plots in order to analyse: pH, electrical conductivity (EC), soil organic carbon, cationic exchangeable capacity (CEC), aggregate stability (AS), and hydrophobicity. The results indicated that: i) prescribed fire only had significantly effects in CEC just after the fire; 5-years after, there were no significant differences between the unburned and burned plots, but two soil properties significantly changed when burned soil samples from 2016 and 2011 were compared: EC and AS in the fraction of 0.053-0.125 mm. In general, the soil properties were not substantially modified by the prescribed fire, supporting the idea it is a very useful tool with very low impact for managing Mediterranean rangelands in order to reduce fuel accumulation and fire risk.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Material selection for a new type of fire extinguisher

Nowadays safety is a hot topic, damage inflicted to human beings is intolerable. Fire safety is a big concern in industrial areas, but in residential areas a lot less precautions are in place. Therefore a new type of fire extinguisher should be developed that should encourage the installation of fire extinguishers in commercial environments and at home. The design of this fire extinguisher has to answer to a lot of demands. From a legal point of view, the extinguisher has to comply with the PED regulations and the EN 3 standard. Extra demands are, given the purpose, superb performance, great ergonomics and an attractive visual design. One of the steps in the design process is to make a material selection based on needed and desired properties of materials. Also the possible processes for manufacturing are an important parameter

An Economic Analysis of Bushfires Management Programs

Allocating scare resources for fire management strategies requires information on the extent of economic losses from bushfires and the efficiency of alternatives. Despite the severity of bushfires, there is no agreed approach in Australia for estimating economic losses from fires nor for evaluating the economic efficiency of alternative suppression strategies. The poster proposes approaches to assess the economic effects of bushfires on local and state economies and sets out models to evaluate the economic efficiency of two key bushfire management strategies: presuppression and suppression. The first model arises from questions concerning the value of pre-suppression (before the fire) fuel reduction activities, and the estimation of an economically optimal fire management budget. The fuel reduction burning aims to reduce losses from a major fire event. To determine how the budget should be allocated, a modification of the Cost plus Net Value Change model is being used. This model has the advantage that each of the influencing parameters is easy to adjust or even change for different areas in Australia. The second model allows straightforward comparisons of approaches to bushfire suppression, through a fire simulation model. The simulation allows comparisons of alternative strategies under similar fire conditions. The economic utility in suppression of fire engines, dozers and aircraft is evaluated using Cost Benefit Analysis and a Cost plus Loss framework. The paper presents useful tools for decision makers to make damage assessment from fire, resource allocation on pre-suppression and guidelines for operational decision making on suppression approaches.Resource /Energy Economics and Policy, A11, H4, Q51, Q54,

Video Based Flame Detection Using Spatio-Temporal Features and SVM Classification

Video-based surveillance systems can be used for early fire detection and localization in order to minimize the damage and casualties caused by wildfires. However, reliability of these systems is an important issue and therefore early detection versus false alarm rate has to be considered. In this paper, we present a new algorithm for video based flame detection, which identifies spatio-temporal features of fire such as colour probability, contour irregularity, spatial energy, flickering and spatio-temporal energy. For each candidate region of an image a feature vector is generated and used as input to an SVM classifier, which discriminates between fire and fire-coloured regions. Experimental results show that the proposed methodology provides high fire detection rates with a reasonable false alarm ratio