The Collapse Process Of High-rise Steel Structure Under Different Fire Conditions Based On Sub-structure Technique

As construction technology development, the building structure system which is getting more and more huge.In construction engineering practice,we must calculate the mechanical properties of structure for large and complex in precisely and rapidly.The birth of the sub-structure technique which is in order to overcome this problem.It is used to calculate the mechanical properties of structure of huge and complex,which uses technology of computer.So this method to calculate is growth ahead in several areas of numerical analysis. In order to convenient to analysis of building structure by computers,we use sub-structure method which save a lot of time in analysis process and reduce the difficulty of structuring models.We also can improve the computing efficiency of computer in the same situation when we use sub-structure method..When the finite element analysis is used to calculate the mechanical properties of large and complex structure,we can use sub-structure method. With the aid of the function of ANSYS,a large finite element analysis software,can reduces repeated work of model product.Meanwhile, it can improve the computing efficiency of computer in the same situation.However,at present the progressive collapse of steel structures caused by fire are more and more frequent and it has caught high attention of researchers from all over the world.In this article, the results of the collapse of steel structures caused by the fire and fire resistance design method which are both in china and abroad will be introduced at the first.And then analyses the fire development process and mechanical properties and physical properties of steel structure under fire condition. Under the base of the previous-mentioned parts, we simulates the whole process of the structure in the standard temperature curve from the beginning of fire to the entire collapse using sub-structure method and considering the effect of geometric nonlinearity, material nonlinearity,status-changing nonlinearity to the model.The main contents of this paper can be summarized as follows:(1)First,this article expounds the context of the theme,meaning of researching and then further introduces feature of steel structure under fire,the concept of the progressive collapse and its development status.Next further describes how to analyze the progressive collapse under fire and what the structure analysis method is.Then presents analysis method which this article employs,that is the analysis model and the analysis method which are based on substructure method.(2)This paper describes how to select substructure model and uses the finite element analysis software ANSYS to simulate and analyze,here static response,dynamic behavior and variation property are focused on in the simulation.Three-dimensional model of steel structure which being analyzed is created with the finite element analysis software ANSYS.The paper intends to analyze the impact of exterior load on steel structure,and the results can provide the theory foundation and related reference for the following research.On the base of this theory, this thesis studies the progressive collapse of high-rise steel structure under fire and proposes preventive measures.It strengthens the introduction of how to prevent fire and how to prevent structure collapse after fire.Finally compared the computer simulation results of three-dimensional model of steel structure with the results of calculating example,and then come to my own conclusions.