Seismic Design of Unbonded Post-Tensioned Precast Concrete Walls with Supplemental Viscous Damping

This paper addresses the use of supplemental viscous damping to reduce the lateral drift of unbonded post-tensioned precast concrete walls under earthquakes. Unbonded posttensioned precast walls are constructed by post-tensioning precast wall panels across horizontal joints using post-tensioning steel that is not bonded to the concrete. These walls have desirable seismic characteristics, such as a large self-centering capability, and an ability to soften and undergo large nonlinear lateral drift with little damage. The greatest disadvantage of the walls in seismic regions is an increase in lateral drift as a result of small inelastic energy dissipation. This paper proposes a supplemental passive energy dissipation system for the walls, using linear viscous fluid dampers. The energy dissipation system utilizes the nonlinear lateral drift that occurs in the walls due to gap opening along the horizontal joints. A design approach for the supplemental energy dissipation system is introduced to reduce the maximum roof drift of the walls to an allowable target roof drift. Nonlinear dynamic time history analyses of a series of walls with different fundamental periods of vibration show that the proposed energy dissipation system and the design approach are effective in reducing the maximum roof drift to prevent significant damage in the walls.