Performance Based Detailing for Bridge Columns

Design provisions that are developed for reinforced concrete bridges subjected to earthquake motion must consider the locations and intensities of inelastic behavior that the structure will endure. Bridge systems are designed to focus inelastic actions in the bridge columns and away from the bridge superstructure, so that the proportioning and detailing of the bridge columns become a critical design quantity. In areas of high seismicity, such as west coast locations in the United States, the columns must be detailed to withstand high levels of inelastic behavior under multiple cycles of loading. Bridge columns in the central and eastern United States present a challenge for bridge engineers because the infrequent earthquake event can be very demanding structurally, yet the design basis is often restricted economically, by considering the likelihood that an event will occur during the lifespan of the structure. A better method is needed to (1) predict the locations and extent of inelasticity in reinforced concrete bridge columns under multiple levels of seismic excitation, and (2) provide appropriate column detailing based on the design event during the life expectancy of the bridge (a performance-based design method). The proposal is to request an additional year of funding to expand the scope of an on-going University of Kansas (KU) NSF grant evaluating the inelastic behavior of a large-scale four-span bridge to develop a new, larger-scale NSF proposal for 2008. New economical photogrammetric methods are being used by the KU team to collect extensive surface deformation data in the hinging regions of a bridge column and further validate the progression of yielding and damage.