| Ultra high performance concrete(UHPC)is a new type of cement-based composite material,which has excellent mechanical properties,durability and working performance,and has been widely used in the field of bridge engineering.At present,engineering practice has shown that there are still some technical problems that are difficult to solve in the existing conventional bridge structure,such as beam cracking,excessive deflection of main span and failure of transverse connection structure of main beam plate,which lead to single beam plate stress and other technical problems,which affect the safety,durability and economy of bridge structure.The emergence of ultra-high performance materials will solve the above engineering problems.Based on the four point bending test of full-scale model of prestressed concrete hollow slab beam,this paper studies the bending performance of hollow slab beam strengthened with ultra-high performance concrete(UHPC)from the aspects of bearing capacity,crack resistance,crack propagation law,section stiffness,natural frequency,etc.,and uses theoretical method for formula derivation and calculation,and uses finite element method for numerical analysis.The main researches are as follows(1)According to the actual bridge structure,three full-scale prestressed concrete hollow slab beams were prefabricated in the factory.Two of them were strengthened with UHPC in the upper part and UHPC in the upper part,and the lower part was strengthened with CFRP.Four point bending test and full-scale model test were carried out on three beams.(2)Based on the test results of three beams,the bending performance,ultimate bearing capacity,crack propagation law,section stiffness and natural frequency of the three beams are compared and analyzed.The relationship curve between deflection and load in the middle span of the beam,the curve of strain distribution in the middle span of the beam,the relationship curve between the maximum crack width and load,and the effect of crack width on the natural frequency of the beam are obtained Ring.(3)Based on the principles of material mechanics and elastic mechanics,the theoretical calculation formulas of ultimate bearing capacity and cracking load of prestressed concrete hollow slab beams are established.The ultimate bearing capacity and cracking load of three prestressed concrete hollow slab beams are calculated and compared.At the same time,the theoretical calculation results are compared with the experimental results.The theoretical calculation results are in good agreement with the experimental results All right.(4)Midas software is used to simulate the test of three beams.C3d8 r solid element is used to simulate C45 concrete.The constitutive relation refers to the code for design of concrete structures(GB 50010-2010),while UHPC refers to the stress curve obtained from the test.The results of finite element simulation,test and theoretical calculation are in good agreement.UHPC reinforcement can effectively reduce the deflection of PC hollow slab beam,restrain cracks and improve the natural frequency of the beam.The plane section assumption of the whole test process is approximately available.Furthermore,the bearing capacity and deformation resistance of PC hollow slab beam are significantly improved,and the tensile strength of reinforcement in tensile stress zone of PC hollow slab beam is enhanced.The overall performance of UHPC strengthened PC hollow slab beam is improved,and the bending performance meets the design requirements.The ultimate bearing capacity of PC Hollow Slab Strengthened with UHPC at the top and CFRP at the bottom increases by 57%.The reinforcement method is more effective for the control of beam changes and beam bottom cracks... |
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