The Forming Mechanism Study About Cracks Of Assembling Prestressed Concrete T Beam In Cold Area

Because of the physical and mechanical properties of concrete,the prestressed concrete structure offen works with cracks.Although the use of performance and the safety of the structure does not affected by these cracks,but these cracks will directly affect the durability of the structures.Therefore,how to avoid the cracks are very necessary for the mechanism of crack formation.The research object of this paper is according to the forming mechanism of cracks of 30 m post tensioned prestressed concrete T beam in northern cold area, the main research contents include:(1)According to the comprehensive analysis and research,summed up in this area(the cold area) existence and distribution characteristics of surface cracks and internal cracks of prestressed concrete T beam.(2)With the help of the software ANSYS to establish the finite element model, to simulate the beam body stress field in different concrete age and strength and in the same prestress tension sequence. To simulate the concrete strength to meet the design strength of 50%,85%,100%;125% to simulate the beam body stress field in the horizontal and vertical deviation of prestressed steel strand.(3)The use of plane stress problem of elastic mechanics and the higher concrete theory, according to the lame solutions to derive the analytic formula of the normal tensile stress field and the radial compressive stress field because of the frost heaving of static explosion of cement paste and the water turns into ice.(4)By means of the frost heaving of static explosion experiment, the analytic formula, the numerical analysis of finite element to simulate the T beam in the various situations and the experimental analysis of static explosion frost heave. To get the distribution law of normal tensile stress and radial compressive stress of prestressed concrete T beam in different cross section in cold area.(5)Through the static explosion experiment, the analytic formula of the concrete,the finite element numerical simulation of T beam with varioussituations,obtains the different section of prestressed concrete T beam in alpine regions of normal tensile stress and the distribution law of radial compressive stress,and the cause and mechanism of the formation of cracks are given.The research of this paper has the greater practical significance. According to the analysis, the measures to prevent the occurrence and development of cracks in the cold area can be put forward. It also can provide the theoretical basis for the future construction.