| The rapid development of economy and society promotes the application of steelstructure in building engineering. At the same time, the building fire accidents result inheavy casualties and loss in recent years. Therefore, in the process of promoting theapplication of steel structure, the study of thermal-structure response of steel structureunder the fire becomes more and more important and necessary.This paper adopts a method of combining performance-based fire resistant designmethod with finite element analysis to study the thermal-structure response of steelframe under the fire. It can get not only intuitive and accurate fire analysis parameters,but also the response state of steel structure in the whole process of fire. A steel frameis taken as the object in this paper. Firstly, Fire Dynamics Simulator (FDS) is appliedto simulate the development process of indoor fire under different fire conditions, andthen get the change of temperature over time in different regions of the interior space.Secondly, temperature measuring points in different positions of the indoor space areused to fit fire temperature curve under the worst indoor fire scene. Thirdly, finiteelement analysis program ANSYS is used to simulate and calculate the temperaturefield within the framework under the fire. The above results are compared with thetemperature field in the standard temperature curve. And then, discuss the differencebetween the two. The study on the simulation and analysis of the response of the wholesteel frame structure under fire in different span is carried out. And then, get the changeof the whole structure in stress, deformation and displacement and so on. The aboveresults are compared to the results in the standard temperature curve. Finally, theinfluence of the thickness of protective layer on the thermal field under indoor fire isinvestigated..Through the above analysis, several conclusions are as follows:(1) The distributionof temperature field of indoor fire is affected by many factors. Especially, the firelocations have a great influence on indoor temperature field distribution and thetemperature distribution of indoor space is not uneven;(2)There is a great differencebetween the indoor temperature distribution field which is simulated by FDS and theresults in the standard temperature curve;(3) Beam-column nodes are the weakpositions of steel structure under the fire, especially stress concentration at the root ofthe flange of beam in the nodes effects on the fire resistance capacity of the beam greatly;(4) The different span under fire have certain influence on the response of thewhole steel frame. Especially, horizontal displacement at the top of the first floor sidespan columns under the fire is bigger than the value of middle span under the fire,while deflection value in the middle span of the beam is relatively small than middlespan under fire;(5) Temperature increase condition has a great influence on thetemperature distribution of steel frame and the response of the whole structure.Compared with the standard temperature condition, the temperature of steel frame atany time under the fire is relatively lower and the displacement of the componentsunder the fire is also relatively smaller, which lead to extend the refractory time of thewhole structure;(6) Fire-retardant coating has a significant effect on the thermal fieldand can effectively improve the fireproof time in fire.(7) The climbing rate of theinternal temperature in the composite beams will reduce gradually and the peaktemperature will decrease obviously with the increment of the coating thickness. Butthey are not linear and direct proportion. Therefore, it is necessary and important forcomposite beams to choose the proper thickness of fireproof coating.The research results in this paper will provide some beneficial exploration andreference for the response analysis of the steel structure under the fire hopefully. |
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