Seismic Design of Bridge Columns Based on Control and Repairability of Damage
C-T. Cheng and J.B. Mander
University at Buffalo
This report describes development of a new seismic design paradigm, Control and Repairability of Damage (CARD). Replaceable/renewable sacrificial plastic hinge zone that use fuse-bar details form the basis of this approach. This special detailing permits repair of damage inflicted on that zone after an earthquake. Another conspicuous advantage, CARD also lends itself to pre-cast and pre-stressed concrete construction. A fatigue theory based on well-known strain-life fatigue concepts for metals is proposed for structural concrete columns. Using this theory, plastic hinges are designed so that fatigue capacity exceeds the fatigue demand expected from a maximum capable ground motion. Well-known capacity design principles are applied to the rest of the structure. To validate the CARD approach, an experimental investigation was conducted. Three 1/3-scale and one near full-size specimens were tested under a variety of cylic load regimes. Results show that the repaired column hinges performed as well as undamaged counterparts, and that damage was constrained withn the hinge zone, thus verifying that CARD enables rapid restoration to full-service followng an earthquake.
Highway bridges. Reinforced concrete bridge columns. Reinforcement. Detailing. Experimental tests. Low cycle fatigue. Capacity design. Plastic hinges. Fuse bars. Control and Repairability of Damage (CARD). Fatigue capacity. Fatigue demand.