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EXPERIMENTAL ASSESSMENT OF REINFORCED CONCRETE COLUMNS WITH DEFICIENT SEISMIC DETAILS UNDER CYCLIC LOAD

To evaluate seismic vulnerability of existing reinforced concrete buildings in Iran, cyclic and monotonic load test on seven columns was carrie out. Four specimens represeented semi-engineered buildings in which seismic provisions are not satisfied adequately. There other specimens represented well proportioned constructions, in accordance with provisions of intermediate ductility, AC1318-99, which is a common reference in Iran. Based on test results, hystersis curves, backbone curves, and idealized curves for two types of columns were established. The semi-engineered specimens showed 35% reduction in strength and 39% reduction in initial stiffness and 35% loss of energy dissipation capacity in comparison to standard ones. Both types of specimens were subject to similar seismic demand, and such reduction of cyclic capacity indicated vulnerability of existing buildings and their need to be retrofitted against seismic action. The tests also showed that concrete spalling started at a drift ratio of about 2% for all specimens and it did not depend on the history of loading. All specimens showed a relatively ductile response with a little pinching in the hystersis curve, and negligible loss of intercycle and outcycle stiffiness. The standard specimens demonstrated relatively good cyclic capacity and confirmed the provisions of intermediate ductility, AC1318-99, for columns..