Elastic-plastic Analysis Of Large-span Prestressed Steel Beam In High Temperature (Fire) Condition

Prestressed steel structure has developed through the past 50 years, from the initial blank on the subject, unfamiliar to it, to the application of it now. With much more attention being payed in recent 20 years, there are one hundred and more largespan prestressed steel structures in our country,whose scales and technical levels have been among the best in the world. Advantages of large-span prestressed steel structure are very prominent, reasonable forced, stiff, light and easy installed. Nearly 10 years large-span prestressed steel structure received extensive attention of science professionals and engineers in the country and abroad, which also has incomparably broad prospect of application. However, prestressed steel structure, including steel structure, has a fatal weakness that its fire resistant ability is very poor. So the importance of steel structure fire resistance is valued by more and more profound significance.In engineering practice, the elastic design is generally used that mechanics research analysis of the structure stress and deformation distribution are used to make the structure deformation limit in the range of elastic deformation. According to the elastic design, it is necessary to ensure the safety of the structure, but in some cases, the elastic design will cause material waste in a certain extent. If the local area appeared certain plastic deformation is allowed within structure, it can better play the performance of the material, so as to improve the bearing capacity of the whole structure.In this paper, on the basis of reading a large number of domestic and foreign literature, and combining the steel structure fire resistance and elastic-plastic research, large-span prestressed steel beam has been studied as the following:(1) Mechanical and thermodynamics theories of prestressed steel beam are summarized the related, and determine how to select material model and parameters of large-span prestressed steel beam under high temperature;(2) Finite element analysis method is used to build model, parameters, and the simulation environment of high temperature(fire), and to determine the transient thermodynamic analysis and structure analysis method;(3) Considering the condition of different span, different prestressed cables mode and different number of prestressed cables, the finite element analysis software ANSYS is used to analyze prestressed steel beam in high temperature condition. It is concluded that how the above three factors affect the rule of ultimate load, deflection change value and loss of prestress on the and the rule: the larger the span is, the ultimate load value is smaller, the midspan deflection values change greater, and the loss of prestress is more mild; compared with direct prestressed cables, curved pretressed cables can enhance the bearing capacity of prestressed steel beam, reduce the deformation, and reduce the loss of prestress.; increasing the number of prestressed cables can enhance the bearing capacity of prestressed steel beam, reduce the deformation, and reduce the loss of prestress.This paper expected to provide some references for design and application of fire resistance in future practical engineering, through a elastic-plastic analysis of largespan prestressed steel beam in high temperature(fire) condition.