Seismic Performance Of Post-tensioned Precast Concrete Segmental Bridge Columns With Viscoelastic Dampers

Incorporating precast concrete components in bridge piers has the potential toaccelerate bridge construction and to reduce the negative impacts that constructionoperations have on traffic flow. Meanwhile, the unbounded post-tensioned(PT)precast concrete segmental bridge columns are capable of undergoing large lateraldeformation with negligible residual drift. The use of precast segmental constructionfor bridge piers has increased in the past couple of decades, but not in regions ofhigh seismicity due to the limited energy dissipation capacity and unknownsregarding the behavior during earthquakes. In this paper, the theoretical andnumerical investigation of unbounded post-tensioned bridge piers with external,fully replaceable viscoelastic (VE) dampers are developed, to further advance thedevelopment of high-performance seismic-resistant bridge piers.(1) Viscoelastic (VE) dampers are one of the most common earthquakemitigation devices. In this paper，based on the requirement of specific installationwithin the bridge piers and energy dissipation capacity, a number of VE dampers aredesigned and fabricated using NBR3305viscoelastic materials. The mechanicalproperties tests of VE dampers are performed to describe its complex characteristicschanging with exciting frequency and strain amplitude. In this study, the Kelvinmodel is used to simulate the performance of VE dampers, which is simple andsmall system of equation, convenient for linear and nonlinear systems. Comparisonbetween the numerical and experimental results shows that the VE dampers can bemodeled by the Kelvin model and the fabricated dampers are effective in reducingthe seismic responses of structures. Meanwhile, this paper addresses themathematical modeling of VE dampers considering the translation and rotationsimultaneously, and analyzes the dynamic behavior of VE dampers installed at thefoot of piers.(2) The lateral strength and deformation characteristics of unboundedpost-tensioned bridge piers with external, fully replaceable viscoelastic (VE)dampers are first developed analytically. Elastoplastic static analysis is performedbased on the fiber model and beam-column element to investigate the response ofpost-tensioned bridge pier. The fiber model adopts multiple linear-elasticcompression-only springs at the rocking interface, combined with viscous materialfor VE dampers and returns encouraging results at global level.(3) Based on the analytical result, a3D nonlinear finite model of a multi-spancontinuous concrete girder bridge is established to assess bridge damage state understrong earthquakes with different types of piers. The analysis specially focus on the reduced dynamic response of the main components of the bridge, such as bearings,abutments and beams, because of the energy dissipation and re-cantering propertiesof hybrid piers with external replaceable VE dampers.(4) The design of both cast-in-place monolithic and hybrid precast concrete piersis presented using the direct displacement-based design (DDBD) procedure, whichare not overly conservative, nor prone to excessive amounts of damage in anearthquake. To calibrate the design procedure, the shaking table tests on4.5-scaledspecimens of the above-designed cantilever bridge piers, namely one cast-in-placemonolithic pier, one unbounded post-tensioned specimen and additionalequivalently reinforced hybrid specimen (combining replaceable VE dissipaters) aredesigned in detail. The experiment scheme also can provide some reference forengineering practice of the hybrid piers.