Experimental Study On Bending Performsnce Of Partially Precast Prestressed Steel Reinforced Concrete Beam

Partially precast prestressed steel reinforced concrete structure as a new type of structure,parts of prefabricated steel reinforced concrete structure combined with the characteristics of the unbonded prestressed concrete structure,achieve complementary advantages.However,at present,there is a lack of research on precast steel concrete structures with prestressed parts in the world,and no relevant regulations or regulations have been formulated.In this paper,the bending behavior of precast steel concrete beams with prestressed parts is studied and analyzed.In this paper,based on the test results of 8 precast steel concrete beams with prestressing parts,based on the available test data and theoretical analysis,the calculation methods of crack checking,flexural bearing capacity of normal section,crack width and flexural stiffness of precast steel concrete beams with prestressing parts at each stage are put forward.The main work is as follows:(1)A total of 8 prestressing partially precast steel concrete test beams were designed in this experiment to study the mechanical performance of PPPSRC beams with different parameters such as prestressing degree,prestressing order,prestressing tendon arrangement form(linear,parabolic)and precast parts,and to compare and analyze the failure pattern,crack resistance,crack generation and development law,bending capacity and bending stiffness of PPPSRC beams.The experimental results show that the crack resistance of PPPSRC beam is obviously better than that of steel concrete beam,and the crack resistance of the precast part can be improved by using ultra-high performance concrete.As with ordinary prestressed concrete structures,applying prestress to the precast part of some precast steel concrete structures can also effectively control cracks and significantly improve the performance in normal service stage.(2)Combined with the actual construction process of PPPSRC beam,the section stress and strain of components in the fabrication stage,construction stage and use stage are analyzed,and the crack resistance checking calculation method for each stage is proposed.(3)Discusses the PPPSRC beam under different design parameters of fracture distribution and development,the increase of prestressed and precast part adopts high performance concrete can effectively restrict the development of crack,combined with the existing calculation methods,considering the prefabricated part adopts high performance concrete tensile contribution,for steel equivalent stress is deduced,the calculation of PPPSRC beam crack width calculation method is put forward;(4)By dividing the section reasonably and referring to the existing stiffness calculation method,the flexural stiffness calculation formula of the test beam is proposed;(5)Combining with the characteristics of the test beam reinforcement and redefine the comprehensive reinforcement index,and found the obvious correlation with test ultimate stress increment of prestressed steel beam,by data fitting,the ultimate stress increment of prestressed steel with comprehensive reinforcement index of linear relation,further put forward the PPPSRC Yang section calculation formula of flexural bearing capacity.