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Estimating the Residual Axial Load Capacity of Flexure-dominated Reinforced Concrete Bridge Columns

Extreme events such as earthquakes have the potential to damage hundreds, if not thousands, of bridges on a transportation network. Following an earthquake, the damaged bridges are inspected by engineers sequentially to decide whether or not to close the bridges to traffic. These inspections are generally slow and resource intensive, potentially leading to traffic disruption on the network for a long period of time. A recent experimental study on reinforced concrete bridge columns demonstrated that the bridge columns designed according to modern design specifications and standards, e.g. California Department of Transportation (Caltrans) Seismic Design Criteria (SDC), exhibited approximately 80% of their original axial capacity after being subjected to cyclic lateral loading up to 4% drift. Thus, bridge columns designed following modern design requirements might possess significant residual axial load capacity even with the presence of moderate to extensive damage. A practical and efficient method for estimating the residual capacity of seismically damaged bridges would expedite bridge inspection and decision making regarding closure by allowing transportation agency officials to use the estimates to triage the on-site, visual inspection that would in turn minimize disruption to the transportation network by preventing overly conservative and unnecessary bridge closures. The objective of this study was to develop a practical mechanics-based method for accurately and efficiently estimating the residual axial load capacity of bridge columns given a level of seismic demand, measured by basic sensors instrumented on the bridge. The practical mechanics-based method for estimating the residual capacity of bridge columns was validated using experimental data from the axial testing of damaged column specimens designed according to Caltrans SDC. From the results of the validation study, the practical method was demonstrated to estimate the residual axial load capacity of bridge columns within approximately 3% accuracy when compared to experimental study results.