| The adjacent prestressed box-girder bridges has become one of the popular bridges in China due to its advantages of easy construction,simple structure,centralized prefabrication ect.However,engineering practice has found that the damage of cast-in-place key joints of adjacent prestressed box-girder bridges is common.On the one hand,the current calculation method of key joints of adjacent prestressed box-girder bridges adopts the articulated plate theory,which assumes that hinge joints act as shear bonds and only transmit shear force,not bending moment.In fact,some research shows that key joints of adjacent prestressed box-girder bridge not only transfer shear force,but also transfer a certain bending moment.On the other hand,the key joints of adjacent prestressed box-girder bridges are made of normal strength concrete,which has poor mechanical properties and low bonding strength with the old normal strength concrete interface.Therefore,it is difficult to meet the use requirements under the composite load of external bending and shear.UHPC has excellent mechanical properties and high interface bonding strength,so it has a broad application prospect as cast-in-place key joints of adjacent prestressed box-girder bridges.In this paper,different types of deep key joints and key joints materials(conventional NSC key joints,conventional UHPC hinge joints,and enhanced UHPC key joints)are discussed.Under the bending and shearing,the crack intensity of key joints interface,the occurrence and development law of key joints interface cracks,and the failure of key joints beams are discussed.After carrying out relevant hinged beam tests,ABAQUS was used to establish the hinged beam model and conduct numerical analysis of the flexural shear performance of the hinged beam.In this paper,the following conclusions are drawn:(1)BAQUS is used to establish the whole bridge model of adjacent prestressed box-girder bridge,and the overall elastic force analysis is carried out to study the force condition of the key joints of adjacent prestressed box-girder bridge.The calculation results show that,under the most unfavorable load,not only shear force but also a certain bending moment is transferred in the transverse direction of the key joints of adjacent prestressed box-girder bridges.(2)In the key joint beam test,the flexural shear resistance of key joint beam(N-U,E-U specimens)of cast-in-place UHPC material is greater than that of the key joint beam of cast-in-place NSC material(N-N specimens).The bearing capacity of N-U specimens was nearly 215.1% higher than that of N-N specimens.The bearing capacity of E-U specimens was nearly 543.4% higher than that of N-N specimens.The N-N and N-U specimens showed cracking and failure at the bonding interface of key joints.The E-U specimen showed shear pressure failure.(3)The weak part of key joint beam is basically at the key joint bonding interface.The cracking load of conventional UHPC hinge joint beam(N-U)and enhanced UHPC key joint beam(E-U)is nearly 477% and 794% higher than that of conventional NSC key joint beam(N-N),respectively.(4)The failure model of E-U specimen is similar to that of integral beam.The inverted T-type UHPC key joints can firmly connect the prefabricated members together to form a whole with common forces,which can be well applied to adjacent prestressed box-girder bridges.(5)In this paper,the finite element model of key joint beam established by ABAQUS has good applicability.The numerical analysis results of the model are in good agreement with the actual test results.(6)Through the finite element simulation analysis of key joint beam with different moment-shear ratio.Regardless of the moment-shear ratio of key joint beam specimens,the DIC value of key joint bond surface of key joint beam in the form of inverted T-type,key teeth+inverted T-type and key teeth+I-type key joint structure is small,which can ensure the integrity of key joint beam.They can be applied to adjacent prestressed box-girder bridges. |
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