Seismic capacity evaluation of existing reinforced concrete buildings strengthened with a novel prestressing steel frame system for increasing lateral strength

Abstract

In this study, a new concept of seismic retrofit, the Prestressing Steel Frame (PSF) system, is

proposed to improve and compensate for the weaknesses of the existing strength-enhancing

seismic retrofit method. The PSF system, a construction method that maximizes the advantages

of the H-shaped steel frame, innovatively improves the constructability and integrity of existing

reinforced concrete (R/C) frames and reinforcement joints. This method is a type of typical

strength-increasing reinforcement method that facilitates calculation of the required seismic

reinforcement amount, and easily enhances the horizontal strength of shear collapse-type R/C

buildings with non-seismic detailing. To review the seismic performance of the proposed PSF

method, pseudo-dynamic tests were conducted on a real two-story frame based on an existing R/C

building without seismic detailing, and seismic performance was evaluated in terms of load and

displacement characteristics, seismic damage level, strength enhancement effect, and displacement

control. In addition, based on the results of pseudo-dynamic testing, a hysteresis model was

proposed to perform non-linear dynamic analysis of the seismically reinforced structure (twostory

frame) with the PSF method. Non-linear dynamic analysis was performed based on the

proposed hysteresis model, and the results were compared against that of pseudo-dynamic

testing. For the commercialization of the method, non-linear dynamic analysis was conducted

on the entire R/C building reinforced with PSF, and the effectiveness of seismic reinforcement

was verified by comparing the seismic response load and displacement response before and after

reinforcement. In the event of an earthquake with a maximum ground acceleration of 200 cm/s2,

which is 2/3 of major earthquakes with a 2400-year recurrence interval stipulated in Korea

Design Standard (KDS) 41, shear failure is expected for R/C buildings with non-seismic detailing,

while small-scale damage is predicted for buildings reinforced with the PSF method. This shows

that the PSF strengthening method is effective in minimizing earthquake damage.