Study On Mechanical Properties Of UHPC Connection Joints Of Assembled Bridge Piers

Compared with the traditional cast-on-site piers,the assembled piers have the advantages of shorter construction period,smaller construction site,less impact on the surrounding environment and traffic,and are especially suitable for the construction of urban viaducts.(1)In this paper,three sets of scale pier specimens are prepared,including different connecting technique such as casting-on-site totally,sleeve-connection and UHPC connection.The static test and low-cycle repeated load test are carried out on these three sets of test pieces.The failure modes and hysteresis curves of the three sets of test pieces are obtained.(2)Horizontal load and the vertical load with 0.1 axial compression ratio are applied to the specimens in the static tests.The load-displacement curve of the UHPC connecting pier is close to that of pier casted-on-site.UHPC connecting pier have a higher bearing capacity,and the failure modes of them are large eccentricity damage.The load-displacement curve of the grouting sleeve connecting pier has a sudden drop after reaching the maximum bearing capacity.During the destruction process,the number of cracks is significantly less,and the interface between the pier and the cap is cracked.(3)The low-cycle repeated load together with the 0.1 axial compression ratio vertical load are applied to specimens in the tests.It is found that the mechanical properties under repeated load of UHPC connecting pier and the cast-in-place pier are basically the same.The hysteresis curves of them are almost coincident,and the shapes are relatively full,which showing the characteristics of the typical reinforced concrete structure bow hysteresis curve.In terms of energy consumption,UHPC connecting piers are better.Due to the influence of slippage,the hysteresis curve of the grouting sleeve connecting the pier is relatively full,and the corresponding energy consumption capacity is worse than the UHPC connecting pier and castin-place pier.(4)The finite element models of pier casted-on-site and pier connected by UHPC are established by ABAQUS software.The basic shape of the hysteresis curve obtained by numerical simulation is in well agreement with the experimental results.The numerical simulation shows that the hysteresis curve of the UHPC joint bridge pier is fuller than that of the pier casted-on-site at the later stage of loading,which shows that its energy consumption is stronger,and which is consistent with the test results.However,due to the difficult effect of the bond-slip effect between steel and concrete,the hysteresis curve obtained by numerical simulation has some differences at the unloading stage compared with the test results.Through above research,the mechanical properties of the UHPC joints of the Assembled piers are basically consistent with the cast-on-site joints,and are superior to the mechanical properties of the grouting sleeve joints of the existing bridge piers.Assembled bridge pier connected by UHPC is worthy of further research and application.