Retrofitted Concrete Bridge Columns Under Shaketable Excitation

Abstract

After the San Fernando Earthquake in 1971, single-column bridges were initially identified as the most vulnerable to earthquake damage and subsequently retrofitted with steel and carbon fiber jackets. This article reports on a study of the performance of these retrofitted columns. Three, 1/3-scale, circular flexure-dominated, retrofitted, reinforced concrete bridge columns were studied using the University of Nevada, Reno, seismic shaketable system. The study compared two steel jacket retrofit columns and one carbon fiber retrofit column to a previously studied as-built column. Simple analytical models for moment-curvature and nonlinear analysis were used to compare calculated performance versus measured. The results showed that Caltrans retrofitting procedures improve both capacity and ductility of as-built columns using either steel jacket shells or carbon fiber sheets. The steel jacket retrofit columns showed increased capacity and ductility over the as-built but were adversely affected by low level motion and variable load path. Load path has a measurable effect on initial performance of reinforced concrete bridge columns subjected to dynamic excitation. The authors conclude that simple time-history analytical models can predict the performance of the columns adequately, although lap splice degradation is not well predicted by these models.