The Establishment Of The Fire-resistance Model Of The Whole Steel Structure And The Finite Element Analysis

With the rapid development of steel industry in recent years, and continuous improvementof the steel structures construction technology, the proportion of steel in the construction fieldis increasing, especially for the complex public buildings and high-rise buildings. The steelstructure is easy to removal and install, the high material strength, short construction periodand other unique advantages of the steel make it to be the best choice of such buildings. Butthe fire resistance of the steel is very poor, the limitations in terms of building fire protectionhas become the fatal flaw to the development of steel structure, the material performance ofsteel under high temperature fire will change dramatically. If the steel structures are notapplied with reasonable fire protection, the local damage will produce in a very short time,resulting in the collapse of the whole structure and causing harm to humans and the building.At present the design method based on the calculation of the steel structure fire resistancecan accurately simulate the boundary constraints and various types of loads of the structures,so it was used by most of scholars and research institutions at home and abroad. Most currentfinite element model of steel frame structures are established with rectangular floor across theentire structure, however, there exist a large number of corners in the actual structure of thebuilding project, this kinds of structure itself has asymmetry, so its mechanical property isinevitably different with the overall structure in high temperature.In this paper, the author study a multi-steel frame structure that used in practicalengineering with the large finite element analysis software ABAQUS, the establishment of theoverall steel frame is done by writing inp file directly, then do some analysis and numericalsimulate about fire resistance in ABAQUS/Standard. Firstly, the heat transfer analysis about asingle steel beam in ISO834temperature-time curve is conducted to get the temperature fieldabout different nodes at the section of I-beam, to compare temperature of different heightnodes changing with the time and the temperature gradient at the section of I-beam. Then ahighly nonlinear distributing temperature load along section is applied to the overall structurewith static analysis. According to that the fire happen in different position, this paper set upthree kinds of condition, investigating the changes of displacement of the second beamwithout fire protection in the vertical direction along the beam axis, deformation of theconcrete slab structure under different conditions and the occurrence position of the maximumdisplacement and stress of the overall structure when fires happened in the different room.Through the analysis and comparison of the mechanical properties of the whole structurewhen the fire broke out in different rooms can find that the fire resistance of building withasymmetric edges structure under fire depends on the fire location to a large extent. When thefire room is in the corners, the damage of steel beams and columns is more obvious. Thestress distribution on two sides of the floor is in a larger difference, the large temperature difference at the junction between fire room and non-fire room leads to greater stress aroundthe floor. Through the analysis and numerical simulation of the overall structure about fireresistance, this paper investigated the response of asymmetric structure under local fire, andprovided some beneficial thought for design of buildings in fire resistant.