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In this paper, the importance of displacement history and its effects on performance limit states, the relationship between strain and displacement, and the spread of plasticity in reinforced concrete structures is explored. An experimental study is currently underway to assess the performance of thirty circular, well-confined, bridge columns subjected to various unidirectional displacement histories including monotonic, reversed cyclic, and earthquake time-history response. The test variables include load history, transverse reinforcement detailing, axial load ratio, aspect ratio, and longitudinal steel content. Longitudinal reinforcing bars were instrumented to obtain strain hysteresis, vertical strain profiles, cross section curvatures, curvature distributions, and fixed-end rotations attributable to strain penetration.

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Described in this paper are strain limit states for reinforced concrete bridge columns. A total of 30 large scale reinforced concrete bridge columns were subjected to either reversed cyclic loading or real seismic load histories as part of this research program. Through the use of a non-contact three-dimensional (3-D) position measurement system, accurate strain measurements that are not possible with conventional instrumentation were made, which allowed for development of strain limits for serviceability, spiral yielding, and reinforcing bar buckling limit states. The proposed bar buckling strain limit was compared to an existing drift-based approach and one formulated using finite element analysis for columns in the data set and the literature.