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 grav ity 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 constructe d with strength and reinforcing details compatible with current nonsei smic provisions of ACI 318-89. The model was tested using simulated ea rthquakes representing minor, moderate, and severe seismic risks for l ow to moderate earthquake zones. The experiments were performed on the ''shaking table'' at the State University of New York (SUNY) at Buffa lo using constant acceleration similitude, assuming material scaling i dentity. The performance of subassemblages, i.e., columns and beam-col umn joints, was also studied experimentally at the same scale to deter mine the strength and deformation capacities of the structural compone nts. The behavior of the subassemblages was presented in the first pap er of this series.(1) Comparative analytical evaluations of the respon se of the structural system were carried out using plastic (limit) ana lysis, nonlinear quasistatic pushover analysis, and full nonlinear tim e history dynamic analysis. The analytical and experimental performanc e of the model building shows that substantial lateral resistance deve lops in spire of the structure being designed only for gravity loads ( U = 1.4D + 1. 7L), without due regard to seismic loads and special det ailing 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.