Behaviour of 1/6 scale model bridge columns subjected to cyclic inelastic loading

Circular, spirally reinforced concrete bridge columns were subjected to cyclic inelastic loading in the laboratory. The bridge columns were one sixth scale models of prototype columns designed in accordance with current California Department of Transportation specifications. A total of six models were tested. Three of the models were constructed with microconcrete, and three were constructed with ready mix concrete using pea gravel. Variables included the aspect ratio, magnitude of axial load, and the use of microconcrete versus ready mix. The models were subjected to slow reversed cyclic loading with the axial load held constant. Results from the tests are presented in the form of energy absorption, load displacement curves, longitudinal steel strains, and displacement profiles. Comparisons of the ultimate moment capacities, measured displacement ductilities, plastic hinge lengths, and the failure mode for the six models are discussed. Comparisons with previous studies are presented along with a discussion of design codes in the United States, New Zealand, and Japan. A series of graphics based computer programs, developed to speed the analysis and interpretation of the experimental data, are discussed. Source code is provided (A).