Safety Analysis Of Steel Frame Structure After Fir

Steel frame structure is one of the main forms of steel structure,which has advantages such as large span,strong bearing capacity,and lightweight structure,and is widely used in industrial plant buildings.Although steel,as the main component material of steel structures,is not easily combustible,its fire resistance is poor.Domestic and foreign research shows that during a fire,steel frame structures will experience internal force redistribution,component deformation,structural damage,collapse,and other responses,which threaten people’s life and property safety.Therefore,to accurately evaluate the actual stress state of steel frame structures after a fire,complex safety analysis is required.In order to shorten the post-fire safety assessment analysis process of steel frame structures,finite element simulation analysis was performed,and a safety analysis system was developed to verify the post-fire safety of steel frame structures.The main research content and results of this thesis are as follows:(1)For the safety analysis of steel frame structures after a fire,it is essential to have a grasp of the basic concepts of safety theory,commonly used identification methods,and structural safety assessment standards.Common identification methods include empirical methods,practical identification methods,probabilistic identification methods,and numerical simulation methods.When conducting thermal-structural coupling analysis,it is necessary to understand the thermal properties of materials,methods of thermal-structural coupling,and principles of heat transfer,among other fundamental theories.These theories serve as important references for subsequent safety analysis of steel frame structures after a fire and are elaborated in detail in Chapter 2 of this thesis.(2)In order to conduct safety analysis of steel frame structures after a fire,it is necessary to collect relevant data such as the geometric shape of the structure,material properties,load conditions,as well as post-fire mechanical performance,component temperature distribution,and structural deflection.Therefore,the ABAQUS finite element software is used for thermalstructural coupling analysis of steel frame structures.Additionally,to study the influence of different fire scenarios on the post-fire mechanical performance of the structure,temperature loads are applied using both the ISO834 standard temperature-time curve and hydrocarbon fire temperature-time curve,and the results are analyzed.The results show that significant deflection occurs at the mid-span of the frame beams in the fire-exposed room,and the highest fire temperatures are observed in the directly exposed components.Furthermore,due to the faster temperature rise in hydrocarbon fires compared to the ISO834 standard curve,the deformation of components in hydrocarbon fire scenarios is much greater than that in standard fire scenarios.At the same time,the load-bearing capacity of fire-exposed components and the physical parameters of steel materials also significantly decrease.This aspect will be discussed in detail in Chapter 3 of this thesis.(3)After completing the thermal-structural coupling analysis of the steel frame structure,safety analysis is conducted using the safety analysis equations from the safety analysis methods based on the simulated data.This analysis aims to comprehensively assess the safety level of the structure.To achieve this,safety analysis equations for the load-bearing capacity and normal serviceability of the frame beams and frame columns are established based on the Technical Specification for Fire Protection of Building Steel Structures.The formulas and steps for safety analysis are presented in detail.A numerical example is provided for comparison to validate the accuracy of the safety analysis method.By employing this approach,the strength,stiffness,and stability of the fire-affected components in the structure can be comprehensively considered,resulting in more accurate results.Additionally,it provides theoretical support for the development of safety analysis systems.This part of the research is elaborated on in Chapter 4of this thesis.(4)Based on the established safety analysis equations and the data from the thermalstructural coupling analysis,a safety analysis system for post-fire steel frame structures has been developed using the C++ programming language.This system is designed to perform safety analysis on post-fire steel frame structures.It is capable of reading input files(inp)and result files from ABAQUS,extracting information such as the maximum temperature experienced by fire-affected components,post-fire structural behavior,section parameters of components,and the elastic modulus of steel materials,and then outputting the analysis results.To enhance the user-friendliness of the system,the Qt software is employed for window design.Detailed descriptions of each window’s design and operational steps are provided to assist users in utilizing the post-fire steel frame structure safety analysis system effectively.This aspect of the research is extensively discussed in Chapter 5 of this thesis.(5)Finally,taking a steel frame structure exposed to a standard temperature-time curve for 30 minutes and a four-story three-span steel frame structure as examples,important components from the fire-exposed room are selected.The safety analysis equations are used to calculate and compare the safety of these structures before and after the fire.Through these case studies,the research methods and procedures of the safety analysis system are explained,which contributes to a better understanding of the research findings in this paper.The calculation results demonstrate that before the fire,the important components of the steel frame structures are in a reliable state,and the structure remains intact.However,after the fire,these important components lose their safety,leading to structural failure.This section will be discussed in detail in Chapter 6 of this thesis.