Post-Fire Susceptibility to Brittle Fracture of Selected Steel Grades Used in Construction Industry—Assessment Based on the Instrumented Impact Test (original) (raw)
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Materials
The results of experimental research on forecasting post-fire resistance to brittle failure of selected steel grades used in construction are presented and discussed in this paper. The conclusions are based on detailed analysis of fracture surfaces obtained in instrumented Charpy tests. It has been shown that the relationships formulated based on these tests agree well with conclusions drawn based on precise analysis of appropriate F–s curves. Furthermore, other relationships between lateral expansion LE and energy Wt required to break the sample constitute an additional verification in both qualitative and quantitative terms. These relationships are accompanied here by values of the SFA(n) parameter, which are different, depending on the character of the fracture. Steel grades differing in microstructure have been selected for the detailed analysis, including: S355J2+N—representative for materials of ferritic-pearlitic structure, and also stainless steels such as X20Cr13—of martens...
Technical Transactions, 2021
In this article, changes occurring in structural steel after exposure to fire are described and discussed. The steel structure before and after fire determines its susceptibility to brittle cracking. The individual phases of cracking are described and interpreted on the basis of a load-displacement graph, directly obtained from the Charpy impact test. The relationship between the intensity of individual fracture energies and the type and appearance of the sample fractures are demonstrated. The program of planned Charpy impact tests and expected hazards after the exposure to fire of selected steel grades are presented. Standard simplified load-displacement graphs are assigned to the steel transition curve. The course of various cracking mechanisms occurring in the case of brittle fractures and plastic fractures are discussed. The aim of this article is to evaluate the possibility of the assessment of structural steel after a fire based on results obtained during the Charpy impact test.
POST-FIRE MECHANICAL PROPERTIES OF STRUCTURAL STEEL
8th National Steel Structures Conference, Greece, 2014
This paper presents a review of the mechanical properties of structural steel exposed to fire and cooled down. The existing design codes do not provide satisfactory recommendations concerning the post-fire properties of steel or the post-fire performance of a steel member, which shows the need for further research on the topic. Experimental results from laboratory tests, including samples taken from real fire damaged steelwork, are collected herein. The available data are analyzed in order to evaluate the residual capacity of fire damaged steel, i.e. the elastic modulus, the yield and ultimate strength and the remaining ductility, which are related to its reuse. For this purpose, simplified formulas are proposed for the estimation of the post-fire mechanical properties of structural steel according to its type.
Post-fire assessment and reinstatement of steel structures
It is widely accepted that many steel structures remain their integrity after fire while their reuse and reinstatement is a critical economical issue. Although significant quantitative research has been conducted the past years, in most cases the stability of the structure as a whole is not addressed, hence no specific guidelines and code provisions have been established for the proper appraisal and rehabilitation of fire damaged structures. This article presents technical aspects of the assessment method and evaluation of fire damaged steel structures, from which useful conclusions are drawn for the safe reuse of the structural elements and connection components, while the reinstatement survey is also comprehensively described. To reliably evaluate the remaining strength, the understanding of the mechanical properties of damaged steel after a fire event is a requisite. Moreover, the current work focuses on the behavior of structural normal steel (hot rolled and cold formed) as well as high strength bolts after exposure to elevated temperatures. Information on stainless steel, cast iron and wrought iron is also presented. Due to the complexity of the issue, an elaborate presentation of the mechanical properties' influencing factors is followed. Subsequently, a wide range of experimental studies is extensively investigated in the literature while simplified equations for determining post-fire mechanical properties are proposed, following appropriate categorization. According to the parametric investigation of the aforementioned data, it can be safely concluded that the most common scenario of buildings after fire events, i.e. apart from excessively distorted structures, implies considerable remaining capacity of the structure, highlighting that subsequent demolish should not be the case, especially regarding buildings of major importance.
The Effect of Fire after Earthquake on Bending Steel Frame Structures
Increase in the level of structural damage, following the fire after the earthquake could cause damages more than the face of the earthquake alone. Because the fire after the earthquake includes several fires at the same time and is complex which occur due to the earthquake and can cause social and economic damages. Experience gained from past earthquakes showed that steel structures were very vulnerable against the risk of fire spread. If a steel frame placed under high heat, quickly due to reduced mechanical properties of steel at high temperature its safety seriously threatened frame. Steel frames have been formed of beams and columns that are connected by the connections. Therefore, one of the most important components of steel structures that transmit force of members to each other and mainstays are responsible for connections among members. Strong earthquake can cause significant damages to infrastructure and possible structures of the urban areas. Past events have proven that lack of attention created a lot more damages than the earthquake itself and will cause catastrophic accidents with high fatalities and casualties. This article intended to review the effects of fire after the earthquake on steel frames. In order to collect data, two methods of use of library and documents searching and sources were used to identify different aspects of the topic and the results were presented.
Post-earthquake fire resistance of steel buildings
Journal of Constructional Steel Research, 2017
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Civil engineering infrastructures journal, 2020
Two fire accidents took place in the Plasco Tower in Iran and Grenfell Tower of London in 2017. Although both of them have led to human tragedies, post-earthquake fire can cause more irreparable damages and catastrophes in larger extents. Engineering structures are subjected to different loads during their lifetime, which may cause damage or secondary loading effects. Evaluation of durability and stability of fired structures and the effects of seismic loading are considered to be significant parameters in fire engineering. The aim of this study is to evaluate and compare durability of reinforced concrete and steel frames during fire loading and post-earthquake fires. In this study, two 7-story steel and reinforced concrete frames are exposed to the fire load. At first, steel and concrete sections are put under various thermal loads in order to compare the method of their heat transfer. Then, the effects of crack on heat transfer of concrete sections are studied. Afterwards, the sel...
Review of Fire-Related Damage of Steel Offshore Structures
The Journal of The Institution of Engineers, Malaysia
Fixed offshore structures are continuously exposed to risk of hydrocarbon fire or cellulosic fire. Hydrocarbon fire generally causes more detrimental effect than cellulosic fire because the rapid increment of temperature gives little response time for people to evacuate the location or to put off the fire. Metallography tests have demonstrated that steel structures continuously exposed to temperature escalation from fires will lose their mechanical properties such as yield strength, tensile strength, toughness, hardenability and elastic modulus. Thus, to understand the structural response during fire, structural integrity assessment with revised steel mechanical properties is advised to be performed. The outcome of the analysis helps to identify the hotspots of the steel structures due to the fire and allow the investigation team to further perform detailed inspection and proposed structural repair to reinstate the integrity of the steel structures.