Seismic Design of Bridge Columns Based on Control and Repairability of Damage

摘要

This report describes the development of a new seismic design paradigm referredto as Control and Repairability of Damage (CARD). Replaceable/renewable sacrificial plastic hinge zones that use fuse-bar details form the basis of the approach. Hinge zones are deliberately weakened with respect to their adjoining elements; all regions outside the hing zones are detailed to be stronger than the sacrificial hinge (fuse) zone and remain elastic during seismic loading. The special detailing of the sacrificial hinge zone permits repair of damage inflicted on that zone after an earthquake. The CARD design methodology also lends itself to the use of precast and prestressed concrete construction. This is considered to be a particularly attractive proposition for bridge design and construction, since historically bridge piers have always been constructed of cast-in-situ concrete, inevitably requiring a longer on-site construction time-frame. To validate the proposed new design philosphy, an experimental investigation was conducted. Three one-third scale model columns (279 mm diameter and 1524 mm high) and one near full-size scale model column (610 mm diameter and 3048 mm high) were constructed and tested under a variety of cyclic loading regimes. Lateral loading included constant amplitude fatigue tests and incremental amplitude tests with drifts up to 5%. Experimental results show that each of the repaired column hinges performed as well as their undamaged original counterparts. Damage to the specimens was controlled and constrained within the hinge zone. The experiments verified that this new approach to construction enables rapid restoration to full service immediately following an earthquake.