The Earthquake Engineering Online Archive

The seismic behavior of critical regions of reinforced concrete components as influenced by moment, shear and axial force

Atalay, Mehmet Bilgin; Penzien, Joseph

UCB/EERC-75/19, Earthquake Engineering Research Center, University of California, Berkeley, 1975-12, 235 pages (515/A85/1975)

Building response caused by moderate to severe earthquake excitation is often in the inelastic range; thus, to enable reliable predictions of overall performance, the energy absorption and failure characteristics of individual components must be established. For reinforced concrete frame buildings, the critical or yielding regions may occur in either or both the girders and columns subjected to various combinations of bending, shear, and axial load. To determine the characteristics and modes of failure of columns under excitations causing degradations in stiffness, strength, and energy absorption, a series of twelve members simulating a column between inflection points above and below a floor level were designed and tested dynamically. The variable parameters introduced were (1) magnitude of applied axial load chosen to represent lower, intermediate, and upper story columns, (2) lateral reinforcement percentage chosen to study the influence of confinement on ductility, and (3) history of controlled lateral displacement chosen to determine the effects of rate and sequence of loading. The results of these tests show that (1) increasing the applied axial load decreases the ultimate lateral displacement capacity, enhances the degrading mechanisms of strength, and stiffness, and, when the axial load is sufficiently high, causes changes in the failure modes from ductile flexure behavior to more brittle shear and buckling behavior, (2) decreasing the lateral reinforcement percentage decreases the ultimate lateral displacement capacity and enhances the degrading mechanisms. All experimental data from these tests have been analyzed and correlated to characterize the energy absorption, stiffness, and strength degradation mechanisms, the modes of failure, and the ductility capacities. In addition to discussing the above-described test program and its correlation studies, this report presents a mathematical model for reinforced concrete columns which predicts force-deformation characteristics under inelastic cyclic conditions. This model can serve as a subelement in an overall mathematical model of a building.

Available online: http://nisee.berkeley.edu/documents/EERC/EERC-75-19.pdf (9 MB)