Lightly Reinforced Concrete Beams under Cyclic Load


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Title: Lightly Reinforced Concrete Beams under Cyclic Load

Author(s): Charles K. Nmai and David Darwin

Publication: Journal Proceedings

Volume: 83

Issue: 5

Appears on pages(s): 777-783

Keywords: beams (supports); cyclic loads; earthquake resistant structures;loads (forces); reinforced concrete; reinforcing steels;strains; stresses; structural design.

Date: 9/1/1986

The behavior of lightly reinforced concrete beams under severe cyclic loading is studied. Seven cantilever beams were tested. The beams had reinforcement ratios of .69 or 1.03 percent, stirrup capacites ranging from 78 to 116 percent of the applied shear, stirrup spacings ranging from .10 to .25 of the effective depth, and ratios of positive to negatve longitudinal reinforcement of .5 and .75. Beam performance is evaulated in terms of the total energy dissipated and the member Energy Dissapation Index. The study clearly demonstrates that the cyclic performance of individual members can be improved by reducing the reinforcement ratio, thus reducing the shear induced by severe lateral loading. A reduced stirrup spacing and an increased positive to negative steel ratio at the face of the support A ' /A increase the number of inelastic cylces endured and the total energy dissapated by the cantilever test specimens. However, the study suggests that in a prototype structure, the increased A '/A ratio increases the induced shear, and thus reduces the effectiveness of the increased positive steel.