Experimental Study On Unbonded Prestressed Concrete Composite Box Girder

As the service time of the bridge increases,and large-scale growth in traffic flow,the phenomenon that bridges appeared in varying degrees of damage is more and more common.Especially after a long period of operational use in the small and medium span articulated plate girder,the horizontal connection between the beam and plate has been damaged to varying degrees,leading to serious veneer force phenomenon.As a kind of prefabricated component commonly used in bridge engineering,the structure of the composite beam has the advantages of convenient construction,saving resources,short construction period,low cost,strong integrity,good earthquake resistance.Using composite structure can be achieved very good economic benefits has been proved by a large number of engineering practice.This paper studies the new structure system-prefabricated composite box girder bridge system.The system first assembled by the prefabricated beams,and finally bear the load by the overall box-shaped cross-section which is consists of prestressed prestressed concrete inverted T-beam and cast-in-place roof.In addition,using unbonded prestressed technology in the components of the system can bring many benefits such as construction convenience,lifting light weight,particularly suitable for small-scale construction unit construction.Another,if the pre-inverted T-beam roof as a cast-in-place template,the structure can force by the overall box-shaped cross-section with good integrity,large stiffness.Design of test beams,conducting indoor model bending test to the inverted T after the pouring beam and the combination box girder in order to comprehensively understand the mechanical properties of the composite beam system.Do a comprehensive analysis to each stage of loading to failure process,reaching the change law of the deflection,non-prestressed steel stress,stress increment of prestressed steel strand and the compressive stress of the top beam concrete.Simultaneously,finite element software Abaqus was used to simulate the simulation.The finite element results are in good agreement with the experimental results.It proves that the whole system has good performance,high rigidity,simple installation and convenient construction.It can provide the beam type reference for the structural system of medium and small span bridges,and at the same time can improve the overall performance of the structure under the premise of guaranteeing economy.Do the static and dynamic load test on a real three-span simple-supported continuous inverted T-box girder bridge,and make a comparative analysis with Midas finite element results.The results show that the bridge has sufficient safety reserves under the design load,a enough high natural frequency and a good vibration attenuation characteristic,which satisfies the requirement of safe operation of existing highway load.