SEISMIC RESISTANCE OF REINFORCED-CONCRETE FRAME STRUCTURES DESIGNED FOR GRAVITY LOADS - PERFORMANCE OF STRUCTURAL SYSTEM

This is the second paper in a series dealing with the behavior of gravity load designed (GLD) reinforced concrete frame structures subjected to simulated seismic motion that was investigated in an experimental/analytical study. A three-story 1:3 reduced scale model was constructed with strength and reinforcing details compatible with current nonseismic provisions of ACI 318-89. The model was tested using simulated earthquakes representing minor, moderate, and severe seismic risks for low to moderate earthquake zones. The experiments were performed on the ''shaking table'' at the State University of New York (SUNY) at Buffalo using constant acceleration similitude, assuming material scaling identity. The performance of subassemblages, i.e., columns and beam-column joints, was also studied experimentally at the same scale to determine the strength and deformation capacities of the structural components. The behavior of the subassemblages was presented in the first paper of this series.(1) Comparative analytical evaluations of the response of the structural system were carried out using plastic (limit) analysis, nonlinear quasistatic pushover analysis, and full nonlinear time history dynamic analysis. The analytical and experimental performance of the model building shows that substantial lateral resistance develops in spire of the structure being designed only for gravity loads (U = 1.4D + 1. 7L), without due regard to seismic loads and special detailing provisions. This paper demonstrates how to evaluate the overall seismic performance of a structural frame based on adequate knowledge of component behavior It also attempts to evaluate the safety margins against damage and collapse of the structural system.