Investigation On Hysteretic Performance Of Precast Segmental Hollow Columns With Energy-dissipation High-strength Bars

Compared with cast-in-place reinforced concrete members,precast segment hollow columns(PSBC)could be applied to decrease the impact on the ecological environment and transportation during the construction.The practical application of PSBC is ever increasing to accelerate construction of bridge structures.However,it is difficult for most of the existing PSBC to meet both the demands on self-centering and energy dissipation,which limits the expansion of it in the moderate and high seismic intensity regions.Moreover,most of the published results assume that the columns bottom were fixed,which is greatly different to real status of a bridge with piles and other foundation in the complex geological environment.In this thesis,the energy-dissipation high-strength bars were applied to upgrade the post-yield stiffness of PSHC,which endows the column with excellent self-centering and energydissipation performance.When the effect of pile foundation is considered in PSHC specimens,the hysteretic performance should be explored deeply.The main contents of this thesis are as follows:(1)Accordance with the published tests,a nonlinear FEM model was established and the calculation compared with the experimental results.The author analyzed the influence of mesh density(the number of fibers and integration points)on the numerical accuracy.(2)Four segmental hollow members were studied with the strength of high energydissipation bars being the design parameter.The simulation model was established according to the foregoing approach to study the seismic performance of the specimen.The effects of axial compression,the ratio longitudinal reinforcement ratio and the magnitude of prestress were compared and analyzed.(3)The horizontal p-y,vertical t-z and vertical q-z springs are utilized to simulate the pile-soil interaction.The numerical simulation on the pseudo-static test was carried out to explore the effect of pile foundation on the seismic performance of PSHC.Based upon the foregoing work,several conclusions could be obtained:(1)The simulation are almost consistent with the test results,which verifies the accuracy and reasonability of the FEM approach.The nonlinear simulation are insensitive to the mesh density.(2)If PSB785 or PSB830 prestressed screw-thread bars are applied as energy-dissipation high-strength bars to replace the ordinary energy-dissipation bars,the residual tip drift of a PSHC decreases and the cumulative energy dissipation remains unchanged or slightly increases.Then the author idea to consider the demand of energy dissipation and self-restoring.The increasing axial compression ratio leads to the decrease of residual tip displacement and improvement of the bearing capacity.The increase of longitudinal reinforcement ratio means increased bearing capacity,energy dissipation and residual displacement.(3)When the influence of pile foundation is considered,the residual tip displacement increases and cumulative energy dissipation increases.As energy-dissipation high-strength PSB830 prestressed screw-thread bars are used to replace the ordinary energy-dissipation ones,the residual tip displacement decreases and the energy dissipation slightly increases.