Seismic Performance Of Steel Reinforced Concrete Composite Columns Of Older And Modern Construction

Abstract: Existing concrete buildings lacking seismic details are well known to cause most losses during earthquakes so there is no wonder they are nicknamed killer buildings. In every new earthquake we see more evidence of their vulnerability. Ordinary building are taking the most focus of researchers from all over the world because of the majority of building are reinforced concrete. But one of the most widely used structure system contains steel reinforced concrete (SRC) composite columns. This type has been used since early of 1950 and nowadays most high rise or non-prismatic buildings are built using SRC composite columns. This Experimental study presented addresses the seismic performance of (SRC) composite columns experiencing shear and flexural failures using different concrete grades and confinement details to mimic both existing buildings with old construction details and modern buildings designed and built according to modern codes and construction practices. Test specimens represent exterior columns modeled based on a typical seismic design of a 30-story prototype new core wall-frame tall building and a 20-story prototype gravity existing building. Test parameters considered in this study are target failure mode, axial load ratio, percentage of longitudinal steel, structural steel section, concrete grade, and the transverse reinforcement volumetric ratio. Tests aim to characterize and compare the cyclic response of SRC columns with old and modern construction details. In particular, shear capacity, flexural capacity, residual axial capacity, deformation capacity and engineering demand parameters under different test variables are sought. Backbone curves for numerical simulation of seismic performance of SRC columns are presented. There are fourteen tested specimens divided to three groups; four specimens were tested as pilot, three specimens were tested representing modern building flexure deficient column and seven specimens for old building: five shear deficient specimens and two flexure deficient specimens. This work came out with many conclusions and recommendations for old and modern buildings to overcome the deficiency of SRC composite column. Retrofitting shear deficient SRC columns under high axial loads (>40%) and flexure deficient columns under high axial loads (higher than the balanced load, i.e. compression controlled failure) experiencing moderate to strong ground shaking seems inevitable.