Title: Reinforced Concrete Buildings in Moderate Seismic Zones: Progress and Problems in Evaluation and Design
Author(s): P. Gergley
Publication: Symposium Paper
Appears on pages(s): 427-448
Keywords: cyclic loads; earthquake-resistant structures; frames; loads (forces): joints (junctions); reinforced concrete; structural design; Design
Earthquake-resistant design of reinforced concrete structures has special problems in moderate seismic zones if the possibility of a very large rare earthquake exists. This is the situation in central and eastern North America. The questions and difficulties associated with introducing a seismic design code for the first time are discussed. The seismic risk to a populated region is not reduced much for many years after the code takes effect; only the rehabilitation of existing structures will reduce the risk significantly in a meaningful time frame. The overall behavior of buildings, especially of existing older reinforced concrete buildings, is often nearly elasto-plastic in nature because a mechanism forms soon after the formation of the first hinge and there is little or no overstrength. This may not be an optimum design in most cases. The response of reinforced concrete buildings to moderate ground motions designed only for gravity loads is better than expected, with moderate drifts and no premature brittle failures in most building types. That is not the case for the rare catastrophic earthquake.