Seismic performance of precast segmental bridge columns with resettable sliding joints: feasibility study

Abstract

In an attempt to promote the use of precast segmental bridge columns in regions of moderate to high seismicity, sliding planar joints are adopted to relieve the adverse effects of seismic action. However, despite the ability to survive, the sliding segments often result in noticeable residual relative movements after an earthquake, which require costly repairs. With the increased occurrence of super typhoons, the ability of bridges to resist extreme wind loads is also a concern. It is desirable to improve and provide the system of sliding segments the self-centering capability and sufficient lateral resistance without unduly high prestressing forces. This paper reports the initial findings on an innovative resettable sliding joint system comprising resetting guide keys, concrete interfaces with low coefficient of friction and a partially debonded tendon system. The resetting guide key is essentially a smooth “shear key” with gentle slope. The partially debonded tendon system consists of grouted tendons in ducts provided with soft wrapping around the length of ducts near the interface to allow relative slipping between precast segments during an earthquake. The capabilities in seismic isolation and self-centering of the resettable sliding joint system are investigated both theoretically and numerically. It is found that, with proper choice in the location of resettable sliding joints, the co-existing rocking displacements at the resettable sliding joints during an earthquake are minimal. Key performance indicators, such as the maximum shear forces at the bottom of column, and the residual relative displacements at joints, are reported and assessed.