Seismic Performance Of Self-centering Segment Bridge Piers With External Viscoelastic Dampers

The earthquakes occurred in recent years have induced serious damage of the bridge structures.The damage and residual deformation of the bridges during the earthquakes not only affects the post-disaster rescue and recovery of the society,but also leads huge amount of cost for reconstruction and retrofit of the damaged structures.Self-centering segment bridge pier(SSBP)is a type of innovative structure developed in recent years,which decouples the conventional bridge piers into several segments and being assembled in-site through post-tensioned prestressed steel tendons.It has the advantageous of fast construction,better self-centering capacity and high economic benefits.However,due to the separation of the bridge segments,the self-centering segment bridge pier also has the defect of low energy dissipation capacity,which reduces the seismic performance of the structure in some extent and limits the application of such structure in the high earthquake intensity regions.In this study,aiming at the limitation of the conventional self-centering segment bridge pier,a passive control method is developed by installing viscoelastic damper on the structure.The theoretical analysis,numerical simulation and experimental test are conducted to investigate this issue.The main content of this thesis includes:(1)Extending the Kuruma model,which was developed for the analysis of the precast segment shear wall,for the numerical simulation of self-centering segment bridge pier,the hysteretic performance of the structure is investigated through establishing the finite element model and numerical simulation.From the comparison with the simulation and experimental result of the conventional bridge pier and self-centering segment bridge piers,the effectiveness of this model is validated.Aiming at the limitation of the Kuruma model that cannot simulate the local deformation of the joint,a finite element model of using zero-length element to represent the joint is established.Through the finite element analysis,the simulation results are compared with that obtained from the Kuruma model to validate this model.(2)To improve the energy dissipation capacity and the seismic performance of the self-centering segment bridge pier,a innovative viscoelastic damper with bi-directional energy dissipation capacity is proposed.After the introduction of the configuration of the viscoelastic dampers and the installation scheme,the mechanical models of the damper with only tension,and translation and rotation deformation patterns are developed according to the installation scheme and input direction of the earthquake ground motions.Based on the deformation patterns and the corresponding mechanical model,the finite element model of the self-centering segment pier with viscoelastic dampers are built.Form the hysteretic and dynamic time-history analysis,the seismic performance of the structures with and without damper are investigated.(3)Four test specimen with bottom joint and multi-segment are constructed and used for the pseudo-static test of the structures with and without dampers.Firstly,the cyclic tests of the viscoelastic dampers are conducted to obtain the performance parameters of the viscoelastic material and dampers.Then,the design and construction process,loading and measurement schemes of the experiment are introduced.Based on the test results of the pseudo-static tests,the hysteretic performance of the self-centering segment bridge pier with and without installing the viscoelastic dampers are analyzed,inclding the loading-resisting capacity,lateral stiffness,hysteretic energy dissipation,and stress of the prestressed tendons et al.(4)Aiming at the viscoelastic dampers with tension,and translation and rotation deformation patterns under different earthquake excitation directions,the method for calculating the corresponding equivalent additional stiffness and equivalent additional damping to the self-centering segment bridge pier is derived.Based on the displacement-based seismic design method,the concerned design method for the self-centering segment bridge piers with viscoelastic dampers are proposed.Using the proposed method,a self-centering segment bridge pier is designed.From the dynamic analysis of the finite element model by Open Sees,the effectiveness of the proposed seismic design method is validated.