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Cyclic Shear Behavior of R/C Plastic Hinges.
Ma, S. Y. M.; Popov, E. P.; Bertero, V. V.
National Science Foundation, Washington, DC. Applied Science and Research Applications., March 31, 1976, 13 p.
Results are presented of an attempt to define the actual mechanisms of degradation in stiffness, strength, and energy capacities that have been observed in the critical regions under earthquake-like excitations. The main data analyzed were obtained from tests on nine cantilever beams. After a brief description of the test specimens and test procedures, the general behavior of the beams is discussed, with emphasis on the failure mechanism and how it is modified under different amounts of shear. Conclusions regarding the observed behavior are drawn, and their implications in aseismic design of ductile resisting frames are discussed. It is noted as essential to provide enough shear capacity in possible hinge locations to develop flexural strength. To reduce the potential shear degradation in the critical regions, it is necessary to develop good shear resistances along all the regions where large cracks might occur. The use of closely spaced stirrup-ties and supplementary ties has proven to be effective in improving the rotation and energy capacities of R/C flexural critical regions. In very short beams, however, a major crack traversing the whole section can develop between two adjacent vertical ties. Consequently, these ties cannot function as shear reinforcement. In this case, the use of inclined reinforcing bars appears to be a practical solution.
Dynamic structural analysis; Buildings; Earthquake engineering; Earthquake resistant structures; Earthquakes; Reinforced concrete; Shear properties; Construction joints; Cyclic loads; Seismic waves