AN EXPERIMENTAL STUDY OF DEFECTُ SEFFECTS IN DETAILING ON THE AXIALBEHAVIOR OF EXISTING CONCRETE COLUMNS

In many countries, Reinforced concrete structures are traditionally designed without seismic provision. In particular, non-seismic detailing is specified in the columns. Seismic rehabilitation of old buildings has been a major challenge in recent years. The first step in seismic rehabilitation is evaluation of the existing capacity and the seismic behavior. The purpose of this research is the study of defectُ s effects in the transverse reinforcement details such as: bend type of transverse reinforcement, anchorage of transverse reinforcement, spacing and volume of transverse reinforcement, on the axial behavior of reinforced concrete columns in the existing buildings. On this basis, for investigation of the seismic behavior of RC columns of a real old building in Iran which has been designed and constructed by European engineers in 1940,four concrete specimens with half-scale with the cross section dimension of300 x 300 mm and the length of 1000 mm, have been tested on the effect of vertical axis in the structures laboratory of faculty of engineering of University of Tehran. It should be noted that, all specimens are 28-day compressive strength of 25 Mpa. Samples are made with similar characteristics of old buildings and reinforced with plain bars by 90 and 135 degree bending of transverse reinforcement. Tests results indicated that the column specimens with non-seismic reinforcement detailing, possesses low ductility capacity. In addition, ratio, bending and anchorage of transverse reinforcements are the most important beneficial effect on the stress-strain behavior of concrete .