Fire Tests Research Articles

Influence of thermal strain on concrete spalling

Understanding the susceptibility to spalling of concrete members in case of fire is important to evaluate the residual load-bearing capacity. The investigations of the spalling phenomenon of a concrete mixture using real scale members are necessary but expensive to carry out. Reducing the specimen size leads to an increase of boundary effects that can result in a reduced spalling or absence of spalling. In this study, fire tests were carried out on unrestrained, single-sided exposed, cuboid shaped specimens (0.6 m ×\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ imes$$\\end{document} 0.6 m ×\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ imes$$\\end{document} 0.29 m) as well as unrestrained and steel ring restrained cylindrical specimens (Ø = 0.47 m, h = 0.29 m), which induce different boundary conditions. These fire tests were carried out on two ordinary concrete mixtures. The two mixtures differ only in the type of aggregates (quartz gravel and basalt grit) and were used to investigate the influence of the thermal expansion of the aggregate on the spalling behaviour of the concrete. The results show a significant increase of the spalling depth due to the restrained thermal expansion achieved by the applied steel rings. Additionally, the type of aggregate has a direct influence on the spalling behaviour of a concrete mixture. The reduction of the boundary effects by the steel rings recreate the test conditions in the centre of a large concrete member. Thus, this type of specimen is suitable to determine the susceptibility to spalling of a material (screening-tests) as preliminary investigations to full scale fire tests.

Fire Performance of Endospermum malaccense Cross Laminated Timber (CLT) Treated with Fire Retardant

This study assessed the fire performance of cross-laminated timber (CLT) made from sesenduk (Endospermum malaccense) painted with a fire retardant. Teknoksafe 2407 (Tk-Exterior) and Teknoksafe 2457 (Tk Interior) fire retardants were prepared and applied to the sesenduk CLT. Fire properties such as surface spread of flame test, charring rate test, fire resistance test, and chemical property changes before and after fire testing were evaluated and compared to Control CLT. The results showed that using fire retardant effectively prevented the fire from spreading.

Prediction model of buoyancy-driven flow rate in inclined tunnels with a localized buoyancy source: Emphasis on stratification effects

In inclined narrow and long spaces such as tunnels, the buoyancy-driven flow pattern and the resulting ventilation flow rate are different from those in enclosure-type buildings, because of their large length-to-width aspect ratios. In this paper, the buoyancy-driven flow rate induced by a localized heat source in inclined tunnels was investigated. Theoretical analysis and three series of experiments including non-isothermal or isothermal buoyancy sources, i.e., large-scale fire tests, brine-water tests and helium-air tests were performed. Two typical buoyant flow patterns were identified in the experiments, which are stratified and well-mixed patterns, respectively. Both the stratification pattern and the longitudinal decay rate of temperature rise were proved to be correlated with a dimensionless factor, η=B01/3ΔLsina/(g0′1/2H3/2), which is composed of characteristic parameters referring to both buoyancy source and geometrical configuration. The flow stratification results in stack effect attenuation and consequently ventilation flow rate reduction. A model for predicting the buoyancy-driven flow rate in such spaces was proposed, with special emphasis on the effects of stratification pattern. The predictions were validated with the experimental data, and the necessity for accounting for the stack effect attenuation caused by stratification was proved. The prediction model possesses an explicit expression and can thus provide a convenient tool for design calculations.

The Impact of Various Heating Rates on Real-Time Degree of Hybrid Fire Simulation

Global fire performance of structures in fire is proven to be more advantageous in many cases of engineering practice than the prescriptive fire resistance based on isolated structural member testing. Hybrid fire simulation (HFS) is a novel well-suited method trending in recent years for analysis of global performance of structures in fire. In the principles of this method, the part of a structure which has unknown behavior or is uncertain to be numerically modeled (subjected to fire) would be physically tested, while the rest of the structure is numerically simulated. HFS method enables capturing the beneficial interaction mechanisms evolving between fire-exposed structural members and the adjacent cooler substructure. Due to the continuous temperature increase in a fire test and the existing thermal inertia as well as the rate- and temperature-dependent material behavior of structures exposed to fire, a real-time performance in hybrid fire simulation counts as a necessity. This challenge is more critical for hybrid fire simulations with higher applied heating rates relevant to structural fire engineering. Within scope of this paper, (a) a robust and rigorous approach for real-time HFS is presented; (b) a series of proof-of-concept studies of different hybrid fire simulations with various applied heating rates are carried out for a thermomechanical benchmark problem; (c) the important results of four representative hybrid fire simulations with relevant heating rates to structural fire engineering are discussed; (d) the importance of an appropriate calculation method for stiffness update of the fire-exposed structural member over HFS procedure is highlighted, and e) the precision and accuracy of the applied HFS approach with respect to interface error and real-time degree are evidenced.

Three-dimensional finite element modelling of the fire response of passive and prestressed near-surface mounted (NSM)-CFRP-strengthened reinforced concrete slab strips

This paper presents a numerical study about the fire behaviour of reinforced concrete (RC) slab strips strengthened with passive and prestressed carbon fibre reinforced polymer (CFRP) laminates installed according to the Near-Surface Mounted (NSM) technique. 3D finite element models were developed to simulate fire resistance tests in which the NSM-CFRP-strengthened-RC slab strips were simultaneously subjected to a service load and the ISO834 fire. The CFRP-concrete interface was modelled through temperature-dependent bi-linear bond-slip laws. In addition to the prestress levels applied to the CFRP (0%, 25% and 50% of their tensile strength), the presence/geometry of fire protection (calcium silicate boards) was also assessed. The comparison between numerical and previous experimental results showed the models accuracy in predicting the thermo-mechanical response of fire exposed passive and prestressed NSM-CFRP-strengthened-RC slab strips, presenting a fire resistance decrease when the prestress increased from 0% to 50%, from 13to 6 min when no fire protection was used, and from 152to 127 min with fire protection. The numerical results allowed predicting the decrease of critical temperature in the CFRP anchorages with the prestress increase: 3.4–3.6Tg, 3.0Tg, and 2.1–2.4Tg respectively for prestress levels of 0%, 25% and 50% (Tg – adhesive’s glass transition temperature).

ДОСЛІДЖЕННЯ ВОГНЕСТІЙКОСТІ ПОКРИТТЯ РЕАКТИВНОГО ТИПУ В УМОВАХ ВУГЛЕВОДНЕВОЇ ПОЖЕЖІ

The purpose of the study is to compare the efficiency of reactive fire protection coatings in modelling scenarios of standard and hydrocarbon fires. Methodology. Fire tests were carried out in a small-scale furnace, as regulated by DSTU EN 16623:2015. The linear coefficient of swelling K was determined in accordance with DSTU-N P B V.1.1-29:2010, and the strength of the char layer was measured using a ST-2 structurometer. The chemical structure of the thermolysis products of the fireproof coatings was studied by IR spectroscopy. Results. The study proposes an experimental protocol for assessing the strength of swollen coatings on steel plates under the influence of a standard and hydrocarbon fire. The evaluation method is based on monitoring the physical integrity and mechanical stability of the char-insulating layer formed from the reactive coating under high temperatures. It has been found that the reactive-type coating under the influence of a standard and hydrocarbon fire forms heat-protective char layers, the degree of swelling, mechanical strength and adhesion of which to the metal plate are proportional and differ on average by up to 10 %. It has been concluded that the studied coating Ammokote MW-120 can be used for fire protection of steel structures operated under potential conditions of hydrocarbon fire. Scientific novelty. The study proposes a simple and reliable method for assessing the possibility of using reactive-type coatings for fire protection of metal structures intended for use and certified for standard fire conditions in hydrocarbon fires. Pactical significance is to expand the scope of application of Ammokote MW-120 coating for fire protection of steel structures under the influence of standard and hydrocarbon fires. Keywords: fire protection of steel structures, hydrocarbon fire, intumescent coating, swelling coefficient.

Fire Tests on Unloaded HSSS Short Columns Protected by Intumescent Coating

Fire Tests on Unloaded HSSS Short Columns Protected by Intumescent Coating

Thermo‐mechanical performance of wolframite mineral reinforced siloxane‐modified epoxy‐based intumescent coating for structural steel

AbstractThis study investigated the effects of wolframite on the fire resistance and adhesion strength of intumescent fire‐retardant coating (IFRC) using a siloxane‐modified epoxy binder. The modification of bisphenol A epoxy was confirmed via Hydrogen‐Nuclear Magnetic Resonance Analysis. The IFRC samples were developed with wolframite (0.25–2.0 wt%) and evaluated for Thermogravimetric analysis (TGA), fire resistance test, furnace fire test for char expansion, morphology and chemical composition, adhesion test and water immersion test. This study identified a coating formulation containing 2.0 wt% of wolframite that showed 57.2% improvement in the residual weight, substrate temperature of 176.7°C and produced a compact char. Field Emission Scanning Electron Microscopy showed that the addition of wolframite reduced pore size thereby increasing the char strength. X‐ray diffraction identified iron neodymium compounds in the char layers, which lowered the pore size resulting in lower substrate temperature. X‐ray photoelectron spectroscopy indicated that the antioxidant capability and the carbon content were increased by 6.9% and 50.3% respectively. The adhesion strength was reduced, however, was within the industrial standards of 2.07 MPa. The water immersion test showed a maximum 66.7% reduction (WF2.0) in the water permeation through the coating.

Discussion of thermal activation on heat collection plate of sprinkler heads

Heat collection plates (HCP) are installed above sprinkler heads in some tall halls in the Asia-Oceania region to give faster thermal actuation. In this study, experiments were thus conducted in a fire chamber to determine thermal activation times of sprinkler heads with and without HCP. Three HCP with different diameters were selected and tested with pendent fast response liquid-in-bulb sprinkler heads. A total of 48 sprinklers heads were studied under different conditions of height and pool fire size. The HCP was found to reduce sprinkler activation time in a fire chamber test by up to 61%. Thermal activation time of sprinkler heads was also investigated by the common plunge test in a wind tunnel. Results indicate that activation was delayed by 5%, 18%, and 221% on average by the three HCP. An HCP of pie plate shape with small diameter would alter the physical scenario of heating up the heat sensing element of sprinkler heads assumed in the plunge test. Therefore, the effect of HCP cannot be appropriately assessed in a wind tunnel.

Method for calculating the uncertainty of toxicity of combustion products

To ensure the reliability and accuracy of tests (measurements),the testing laboratory must calculate the measurement uncertainty for eachtest method and reflect this characteristic in its test (measurement) reports.Calculation of test uncertainty is carried out using various methods. In thisarticle, the uncertainty calculation was carried out using the least squaresmethod, when the desired value of the output parameter is determined fromthe graph. For this purpose, a series of tests was carried out: the toxicity ofcombustion products was determined from the lethality of white laboratorymice and a graph of this dependence was plotted. The graph determines thetoxicity of combustion products at 50% lethality of white laboratory mice.Using the least squares method, confidence limits for the estimate of themeasured value were calculated and graphically shown in this graph. As aresult of calculations, the uncertainty of the toxicity of combustionproducts is about 25%; such a large scatter of data using this methodconsists of the error of the measuring equipment and the calibration of thisequipment, the test sample and its composition, as well as thecharacteristics of white laboratory mice and their behavior. These resultsfor calculating test uncertainty can be used for testing laboratories thatconduct fire safety tests of materials.

An algorithm to determine the impact point on the target surface using ultrasonic sensors

The article addresses the issue of using ultrasonic sensors to determine the bullet's impact point on the target surface, serving to evaluate the results of firing tests. The method of determining the impact point is based on the time difference of the time of arrival of the sound wave to the ultrasonic sensors. The constructed equations are complex nonlinear equations. To be able to solve this system of equations, the construction of the equation is combined with the arrangement of sensors to isolate each unknown, helping to simplify the solution of the system of equations. Sensor layout diagram and impact point determination algorithm have been proposed.

The burning rate of wood cribs under forced flow and variable oxygen concentration: A B-number approach

Wood cribs are used in a multitude of fire testing and research capacities including the certification of inert gas extinguishing systems. In these standardized tests, a wood crib is subjected to the joint effects of a variable forced flow through the crib and a systematic reduction of oxygen concentration. These joint effects increase the wood crib burning rate, even at reduced oxygen concentrations, before extinction is achieved by oxygen depletion. Currently, no theoretical frameworks exist for studying these coupled effects simultaneously. To address this problem, the in-depth heat and mass transfer phenomena are examined, and a general mass transfer B-Number is proposed for wood cribs. The methodology presented in this work encapsulates the oxygen reduction effects through the B-Number and the forced flow effects through the heat transfer coefficient. The theoretical burning rate with inputs of experimental flow velocities and oxygen concentrations demonstrates that the initial increase in flow drives the observed burning rate increase in the experimental results. Following the initial increase, the reduction in the oxygen concentration dominates and leads to a decrease in the wood crib burning rate. The combined B-number and heat transfer coefficient approach provides a good representation of the competing flow and O2 depletion effects and correctly captures experimental trends. A more accurate wood crib Nusselt number correlation for the heat transfer coefficient is required to better account for the heat transfer in the complex crib geometry.

Alternative method for stopping the coconut shell charcoal briquette drying process

The drying processes of coconut shell charcoal briquette consist of drying and agglomeration. In industry, the drying process is determined by a quality control person, which creates dependency. The justification was conducted by firing and hardness checking. The firing test consumes a lot of time. An alternative method for determining the stopping drying process is proposed. The method is based on the resistance of the briquette in addition to density. One hundred and fifty cube briquettes of 2,6 cm x 2,6 cm x 2,6 cm in wet, half-dry, and dry conditions were tested for electricity resistance. The results show different resistivity of wet, half-dry, and dry. The dry has a resistivity of 1.82 105 Ω. The others have less than that number by order more than 10. Some doubts were found due to the low resistivity number close to half-dry condition. The density of the doubt was in the type. Therefore, a combination of density and resistance will be used to stop drying, which can be done quickly and out of the dependency of the quality control person.

Campo térmico de lajes mistas em situação de incêndio

Abstract Composite steel decking concrete slabs are an important structural member in building construction. Research on its thermal behavior should be developed to understand its fire performance. In this paper, a comparison of the temperature distribution in the cross-section of steel decking concrete slabs subjected to fire is made through three different procedures: (a) standardized analytical, (b) experimental and (c) numerical. The analytical method was the one proposed in NBR 14323 standard. The experimental tests corresponding to eight real-scale fire tests on composite slabs carried out by the authors. The numerical tests were done for the same configurations of the experimental tests and used the FEA software Abaqus. Steel decking temperatures obtained with NBR 14323 methodologies showed good convergence with the experimental and numerical ones. The same was not observed for the concrete, positive and negative rebar.

Development and Numerical validation of an Aerospike nozzle Contour Design

Aerospike nozzle simplified design and analysis, as well as test results, are presented. New techniques in nozzle design have been used to improve the performance of current rocket engines. The use of an aerospike nozzle is one such technique. It outperforms the existing proven bell nozzle in terms of overall performance. This study analyses the development and flow analysis of an aerospike nozzle at sea level, validating their results by taking into account currently used bell nozzles. The flow over the aerospike pump is investigated in higher depth using computational fluid dynamics under an autonomous fire testing condition. This test showed that the approximate design method used to determine an aerospike nozzle shape can lead to extremely effective nozzles. A model of the current 7.45 kN bell nozzle was selected as a specimen to develop an aerospike Nozzle. Gambit and Fluent software were used to model and examine the flow characteristics of building the aerospike nozzle. The developed aerospike nozzle shows a nearly 2% increase in performance over the existing nozzle.

About the influence of high temperature or fire testing conditions on the tensile behavior of carbon reinforced poly phenylene sulfide laminates

This study aims to investigate the thermo-mechanical coupling in carbon fibers reinforced Poly Phenylene Sulfide (PPS) laminates subjected to critical temperature conditions. In order to dissociate the physical phenomena (degradation/decomposition on the one hand and deformation/damage mechanisms on the other hand) at play in quasi-isotropic laminates (fiber-dominated mechanical behavior), homogenous and fire testing conditions (heterogenous) were considered with or without mechanical loading. X-Ray tomographic and fractographic analyses were conducted to identify the role played by porosities formation (resulting from thermally induced deformations and damages) on the structural bearing capabilities of C/PPS laminates to be used in high-temperature environments. Under high temperature conditions (homogenous temperature distribution), the retention of tensile properties is not well preserved as the axial stiffness and strength decrease of 50% and 75%, respectively. Under fire conditions (heterogenous temperature distribution), the degradation of tensile properties is more dramatic with an 80% decrease.

Study on a Complementary Method to Address the Limitation of Smoke Detectors: Focusing on Carbon Monoxide Sensors

To compensate for the limitations of smoke detectors that frequently emit non-fire alarms, we investigated the carbon-monoxide detection characteristics of smoke detectors using UL 268 fire and non-fire test standards. Large amounts of carbon monoxide were generated during incomplete combustion at the beginning of a fire. Relatively low concentrations of carbon monoxide were also generated under non-fire conditions owing to steam, dust, etc. The response characteristics of general and analog smoke detectors from various manufacturers were analyzed to determine the possibility of linking smoke detectors installed in existing buildings. The experiments revealed that the smoke detectors showed similar reaction characteristics regardless of their manufacturer. However, those equipped with self-made carbon monoxide cross-sensing modules detected different carbon monoxide levels depending on the measurement location or method. Although using a carbon monoxide sensor is effective for distinguishing unwanted fire, additional experiments under various conditions are necessary to establish an appropriate detection range for carbon monoxide based on the response characteristics of the sensor.

Study on the Smoke and CO Alarm Concentrations to Develop a Smoke & CO Combination Detector

In this study, we studied smoke and CO alarm concentrations to develop a combination detector for both smoke and CO. The derivation of smoke and CO alarm concentrations involved examining CO concentrations by smoke concentration using a sensitivity tester, typically employed for the type approval of photoelectric smoke detectors. Fire alarm and false alarm tests were performed to analyze smoke and CO concentrations further. In the fire alarm test conducted with polyurethane foam, generating black smoke with a reduced light scattering effect in the smoke chamber, no fire alarm was triggered, although the fire alarm concentration of the existing photoelectric smoke detector of sensitivity type 2 was set at 15 %/m. The measured smoke concentration reached only up to 10.2 %/m. Conversely, in the false alarm test with sliced pork belly and mackerel, false alarms occurred as the smoke concentration exceeded 15 %/m. The determined smoke and CO alarm concentrations for the combination detectors were established at 7.5 %/m for smoke (continuously for 10 s) and 15 ppm for CO (continuously for 10 s). Applying these concentrations in subsequent tests revealed an improved performance. In the polyurethane foam fire, where the existing smoke detector failed to operate, a fire alarm was issued at 328 s with the newly derived concentrations. For smoldering wood, the combination detector issued a fire alarm 305 s faster than the existing smoke detector. Furthermore, in the false alarm test with hamburger patty, sliced pork belly, and mackerel, the adaptability of false alarms was enhanced.

Fire Resistance Performances of Composite Roofs According to Application and Non-Application of Purlin

This study evaluates the risks of roof collapse for three types of roofs designed for 1-h fire resistance performance: a roof system with a purlin, a roof system without a purlin, and a unit roofing system without a purlin. The roof system with the purlin and the unit roofing system satisfied 1-h fire resistance performance, however, the roof system without the purlin did not. It was determined that the roof systems with and without purlin were at risk of casualties owing to the rapid increases in deformations after 30 min in the fire experimental test. The maximum deformation of the unit roofing system was larger than that of the other systems. However, because the deformation over time showed a linear behavior, the risk of collapse owing to the rapid increase in deformation was considered to be the lowest.

Design and Implementation of Intelligent Fire Monitoring System Based on Multi-Sensor Data Fusion

Abstract To reduce the losses caused by fire, this paper proposes an intelligent fire monitoring system based on multi-sensor data fusion. Through the design of the temperature, smoke and flame sensors, based on the weighted least squares WLS and improved fuzzy support degree of similar sensors and dissimilar sensors data fusion, respectively, in the ZigBee wireless network based on the design of the fire remote monitoring and control alarm for monitoring, and add the local storage and emergency module. In addition, whether the router nodes work on the ZigBee wireless network during the fire test depends on multi-sensor data fusion. The test shows that the node communication distance is extended and can reach the acceptable requirements in the range of 70m, the highest probability of fire occurrence is 0.92, the lowest probability is 0.14, the overall probability of occurrence is in the range of 0.4 to 0.6, and the error between the predicted value of the probability of occurrence of the fire and the expected value is within ±0.05.