A Kalili - Ph.D Candidate of Structural Earthquake Engineering at International Institute of Earthquake Engineering and Seismology, Tehran, Iran,
F. Nateghi-Allahi - Professor of Civil Engineering, Structural Engineering Faculty, International Institute of Earthquake Engineering and Seismology, Tehran, Iran,
A. Farahani - Department of Civil Engineering, Behbahan Khatam Alanbia University of Technology, Behbahan, Iran.

Several methods have been presented for strengthening RC frames and connections. One of the newest methods is using steel prop. In this paper the effects using different yield stresses and sectional areas for the prop on nonlinear behavior of the frames strengthened with this method, have been investigated. For this purpose push-over analysis has been used for analyzing and drawing load-displacement curves of ordinary and strengthened frames. At the next step, by drawing ideal bilinear load-displacement curves, ultimate strength, ductility and modification factors of the frames have been calculated. Then using geometrical and mechanical properties of the prop and concrete, dimensionless curves have been presented for determining mentioned factors. It was investigated that increasing the yield stress of prop, ultimate strength of the frame increases too, but ductility and modification factors of the frame decrease, so that differing yield stress of the prop from 140 MPa to 400 MPa, ductility factor of the frame decreases up to 59 %.

RC frame, beam-column connection, strengthening, steel prop, steel jacketing