| Response of reinforced concrete members subjected to low-cycle, high (displacement) amplitude loading is critically influenced by the bond-behavior between reinforcement and concrete. Earthquake loading is an example of this type of loading. To evaluate performance of structural elements subjected to seismic excitation, bond behavior is usually studied by subjecting specimens under repeatedly applied loading at a quasi-static loading rate. However, the rates of loading under earthquake may be substantially higher than those normally used in the past tests. To evaluate the pull-out behavior of reinforcing bars subjected to cyclic loading applied at varying rates is one of the primary objectives of the research to be reported here.;Small-scale models of reinforced concrete beam-column joints and anchorage-bond specimens were subjected to large cyclic displacements at two rates. The reinforcing bars were grooved to install the strain gages. To assess damage, free vibration tests were conducted. The reliability of the modeling techniques was established by comparison of the results for the slower rate with those obtained from the full-scale tests on prototype. The test results (steel stress distribution, load-displacement response, cracking pattern, energy dissipation, stiffness degradation, moment-curvature, etc.) indicate that the relatively greater extent of damage in the faster rate test specimen was primarily due to the concentrated bond stress along the bar at the faster rates of loading. |
