Fatigue analysis of unconfined concrete columns. Technical report

Current seismic design codes which aim at maximizing the overall ductility of a structural system are a result of extensive experimental and analytical research over the past three decades. In seismic bridge engineering, the state-of-the-practice has lagged by some two decades the state-of-the-knowledge. Thus the vast majority of the bridge structures in most countries, including the United States, have been built to non-seismic codes. Since it is not economically feasible to abandon all of these existing structures, it is necessary to evaluate their expected seismic performance and then retrofit those structures, it is necessary to evaluate their expected seismic performance and then retrofit those structures that are deemed to be seismically deficient. This report is concerned with the first step in the seismic retrofit process-seismic evaluation. Using an energy based methodology it explores the various possible failure in non-seismically designed structures including: unconfined concrete fatigue; bond failure in anchorages and lap splices; compression buckling of the longitudinal reinforcement; fracture and fatigue of the longitudinal reinforcement; and shear failure of the columns.