Papers by Keyword: Fire Damage

Abstract: In chemical processing plants and petroleum refineries, the pressure vessels and pipelines suffered often from fire accidents and thus resulted in the metal materials were in overheating state. Elevated temperature could cause the changes in metallographic structure and have unfavorable effects on material mechanical properties. In order to understand better the influence laws of overheating on metallographic structures and material mechanical properties, the methods of theoretical analysis and experimental research were used and the effects of thermal exposure temperature, duration time and cooling rate on microstructure of low-alloy steel 12MnNiVR, were studied systematically. The study can provide basis data for the material properties database of metal material suffered from fire accident, and afford technical supports in the key technologies on fire damage FFS (Fitness-For-Service) integrity assessment.

Abstract: In chemical processing plants and petroleum refineries, the pressure vessels and pipelines suffered often from fire accidents and thus resulted in the metal materials were in overheating state. Elevated temperature could cause the changes in metallographic structure and have unfavorable effects on material mechanical properties. In order to understand better the influence laws of overheating on metallographic structures and material mechanical properties, the methods of theoretical analysis and experimental research were used and the effects of thermal exposure temperature, duration time and cooling rate on microstructure and mechanical properties of low-alloy steel 12MnNiVR, were studied systematically. In the paper, mechanical testing (hardness test) are carried out to understand changes in the mechanical properties that would be observed in the metal exposed to elevated temperatures during a fire accident. The study can provide basis data for the material properties database of metal material suffered from fire accident, and afford technical supports in the key technologies on fire damage FFS (Fitness-For-Service) integrity assessment.

Abstract: The paper proposes a numerical approach to the problem of residual mechanical performance of load-bearing fire-separating masonry walls, via FE modelling. The mechanical features of the model are oriented to capture the cracking behaviour under both thermal and mechanical stress; by doing so, the liability of numerical outcomes could be assessed by comparison to experimental information already obtained. The numerical analysis is performed by means of FEM analysis with DIANA 9.4.4 software, simulating the experimental heating cycle followed by a mechanical ‘cold’ compressive failure test. The comparison of numerical outcomes to available experimental information allows to judge the good reliability of the numerical approach in reproducing the residual behaviour of a masonry wall after fire exposure; this would especially address the issues of physical modelling and the difficulties of relating the behaviour of small samples to real-size walls.

Abstract: This research intends to evaluate the level of affect of fire damage on the waterproofing layers performance level that are applied to the upper surface layer of underground parking area slab. Samples were collected directly from the fire damage site in order to evaluate how much of the waterproofing performance is retained in the water proofing layer. As per the designed procedure of this research, the involved structures that underwent fire damage were first examined and the samples that were afflicted by the fire damage were visually inspected. The sample collected from the fire damage site was taken and compared with the same undamaged sample type in order to evaluate the difference of the former's waterproofing performance capacity. The conclusion of the research finds that despite the 250mm width concrete surface slab being subjected to intense fire damage, there was no deterioration in the waterproofing layer's performance capacity.

Abstract: Advanced countries have adopted performance-based protective design to evaluate safety of buildings for building’s function of fire protection. And they have employed technology of fire protection engineering and quantified data of theoretical numerical model to create an even more flexible evaluation method for building’s fire protection. Buildings suffered varied degree of attack from elevated temperature and thermal radiation, which leads to changes in physical, chemical and mechanical properties, might result in considerable damage to the buildings and their structure. Such damage threatens populace life. This paper uses FDS (Fire Dynamics Simulator) software to analyze thermal flow field of fire. The temperature boundary condition of simulation results are then entered in the CFD (Computer Fluid Dynamics) software PHOENICS to calculate internal temperature and mechanical property of the beam. This study also integrates related experimental literatures as auxiliary to calculate thermal transmission and strength. Purpose of the above is to investigate elevated temperature and reduction of mechanical property, as well as verify safety of structure.

Abstract: To measure the depth of fire-damaged concrete by ultrasonic method, it was traditionally assumed that the concrete of the fire-damaged structural member could be simply classified into damaged layer and undamaged layer. Based on it, the damage depth can be calculated with a series of single-sided ultrasonic measured data. This method is simple and convenient but less accurate in the practical application. To improve the algorithm, hyperbola curves are adopted to simulate the varying of damage with depth in this paper. And parabolic curves are adopted to simulate the traces of ultrasonic wave in different measured distances. Therefore, the minimum propagation time can be obtained under different damage conditions. Through comparing the calculating results and measured data in different measured distances, the most likely damaged trend can be determined with least square method. At the end of this paper, examples are demonstrated to prove this algorithm feasible and more accurate than the traditional one.

Abstract: The damages to reinforced concrete structures subjected high temperature of fire mainly include the followings: high temperature make the microstructure of concrete be loose and porous, the strength of concrete and steel reduce greatly.The alkaline hydration products of cement was decomposed under the high temperature, which would destroy the alkaline environment of concrete around steel and cause the steel corrosion. In this paper, the machanism of realkalization technique is present. Moreover, method of mercury intrusion pore measurement, SEM analysis and investigation on pH Value of concrete pore solutions experiment were carried out to study the durability repairing efficiency of realkalization technique.

Abstract: There are some reinforced concrete structures exposed to severe environmental conditions might require maintenance or strengthening. Many of these severe circumstances are the result of extreme climate conditions such as low temperature, freeze–thaw action, fire attack, and exposure to deicing salts. Because of this, the environmental durability of both the repair materials and methods used in rehabilitation applications are of utmost importance. A small fire can reach 250°C, while a common blaze can easily produce temperatures of around 800°C. In major conflagrations the temperature can even reach 1100°C. At this level, the heat affects most materials, provoking the spontaneous combustion of some of them and affecting the resistance of others. However, very little research has been performed in evaluating the environmental durability of strengthening materials for concrete members. Very little work has been done on the effects of freeze–thaw cycling on bonding and repair materials. In this study, ultra high performance concrete (UHPC) was used to investigate the effect of strengthening concrete members by fire-damage test or freeze-thaw test. The results show that the mechanical properties of UHPC possess high strength, toughness, and freeze-thaw resistance. The CFRP (carbon fiber reinforced plates) wrapping specimens exposed at 300 °C showed totally failure with the deterioration of the adhesive. The UHPC with bonding 10 mm thickness specimens exposed at 400 °C and duration of 1 hour still in good shape. The UHPC with 1-cm or 2-cm thickness on strengthening concrete members could be obtained specific retrofit effects. The performance of UHPC specimens is better than those of CFRP wrapping specimens during high temperature exposure. The results of slant shear tests show that the bond strength of PC/PC, UHPC/PC and UHPC/UHPC decreased significantly after 600 freeze–thaw cycles or high temperature exposure.

Abstract: In this paper, recycled aggregate concrete subjected to severe fire or high temperature loading condition is investigated. Special attention of the study is devoted to analyze the fire-induced damage and the residual strengths of recycled aggregate concrete. For this purpose, 160 cube specimens are heated under a single thermal cycle of 20oC (ambient temperature), 200oC, 300oC, 400oC, 500oC, 600o, 700oC and 800oC, respectively. Different replacement percentages of the recycled coarse aggregates (RCA) with 0, 30%, 50%, 70% and 100% are considered. Damage and failure patterns of the recycled aggregate concrete specimens are analyzed systematically based on experimental observations. The residual compressive strengths of the recycled aggregate concrete (RAC) at elevated temperatures are studied and evaluated in details. Some differences between the recycled aggregate concretes with different replacement percentages of the recycled coarse aggregates are observed. On the basis of the experimentally measured residual compressive strengths of the recycled concrete, relationships between the residual compressive strengths of the recycled aggregate concrete and the elevated temperature are derived. The results presented in this paper have direct applications in the design and structural analysis of reinforced concrete structures consisting of recycled aggregate concrete.

Abstract: In the present work, the mechanical properties of 321 stainless steel pressure equipments exposed to an accident fire in a chemical unit were investigated. The performance and microstructure of this material were described by chemical compositions analysis, tensile test, scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). The experiment results showed that the mechanical properties of the material were degraded. The grains on the external surface of the fracture became coarse. These results indicated that serious damage to 321 stainless steel had been induced by extreme heat of the fire and this pressure vessel could not be used anymore.