Experimental Evaluation of the Residual Axial Load Capacity of Circular Bridge Columns

Abstract eng:
Evaluation of the post-earthquake capacity of a bridge to carry self-weight and traffic loads is essential for a safe and timely re-opening of the bridge after an earthquake. The ability of a bridge to function depends directly on the remaining capacity of the bridge columns to carry load. An experimental study was conducted to investigate the relationship between earthquake-induced damage in reinforced concrete bridge columns and the capacity of the columns to carry axial load in a damaged condition. Four essentially identical one-fourth scale models of the prototype columns are designed for testing in the cantilever configuration, assuming an inflection point at the column mid-height. A two-stage testing procedure is used. In the first stage, three columns were tested under lateral load by applying a bi-directional quasi-static incremental lateral displacement protocol with circular orbits of displacement up to the predetermined, incrementally increasing displacement ductility targets: 1.5, 3 and 4.5. An axial load equal to 10% of the column’s nominal axial load capacity is maintained during lateral test. At the end of the lateral tests the columns are re-centered by cycling them at very low amplitudes of displacement. In the second stage, an undamaged and the three damaged columns are subjected to a monotonically increasing axial force up to the failure of the column. The residual axial load capacity of the damaged columns without presence of residual lateral displacement is then determined. The test results show a loss of up to 22% in axial load carrying capacity with increasing displacement ductility demand.

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