The Fire-resistance Performance Analysis Of The Whole Process For Simply Supported Prestressed Steel Reinforced Concrete Beam Under High Temperature In Fire

Prestressed steel reinforced concrete structure is a new type composite structure made of concrete, reinforced, section steel, prestressed steel strand, it has the advantages of high carrying capacity, high stiffness, good anti-seismic performance, so it is generally used for important structural members such as large span, heavy load and high-level, conversion components for ultra-high- rise structures. Considering the importance of the prestressed steel reinforced concrete structures in the entire structure, the mechanical properties under high temperature in fire will directly affect the security of the entire structure. Under the action of high temperature in fire, prestressed steel reinforced concrete members will form a section temperature field which is obviously gradient, the elastic modulus of the material will be re reduced, the component will have a greater thermal stress and deformation. The reduction of material strength will greatly affect the carrying capacity of components. Therefore, analysis of the mechanical properties for prestressed steel reinforced concrete structures under fire, is extremely important to improve the security of the structural design.Simply supported prestressed steel reinforced concrete member as the object of study, by contrasting the theoretical analysis and experimental results, analyzed the mechanical properties of simply supported prestressed steel reinforced concrete beam under fire, the main contents include:1. By using the ABAQUS finite element analysis software, analyzed the section temperature field distribution of simply supported prestressed steel reinforced concrete beam in thermal-mechanical coupling status, got general rules of the component section temperature changes by comparing with the experimental measured temperature field. Calculated the high temperature mechanical properties of the constituent materials according to the data of temperature field, revealed the mechanical properties degradation mechanism of the prestressed steel reinforced concrete member under high temperature.2. By analyzing the stiffness of the prestressed steel reinforced concrete member under high temperature, got a method for calculating the stiffness of the simply supported prestressed steel reinforced concrete beam under high temperature. Compared with the measured values of the mid-span deflection under fire in the experiment, verified the correctness of the stiffness analysis, laid the foundation for further analysis of high temperature mechanical properties of prestressed steel reinforced concrete structure.3. According to the section temperature field distribution of the the whole heating process, derived the normal cross section ultimate flexural bearing capacity calculation formula of the simply supported prestressed steel reinforced concrete beam under high temperature. Based on the the formula derived, got the variation law of ultimate flexural bearing capacity during the whole fire process. By analyzing the effective prestress variation from the experiment, established simple calculation formula of the prestress loss in the prestressed steel reinforced concrete under high temperature.