Quasi-static and pseudo-dynamic testing of infilled RC frames retrofitted with CFRP material

The intact infill walls in reinforced concrete (RC) frames have beneficial effects to overall behavior in terms of stiffness, strength and energy dissipation in the event of seismic actions. The rationale of this paper is to increase effectiveness of the carbon fiber reinforced polymer (CFRP)-based retrofitting technique so that intact infill walls of vulnerable mid-rise RC buildings are transformed into a lateral load resisting system. The seismic behaviors of cross-braced and cross diamond-braced retrofitting schemes applied on infilled RC frames have been investigated experimentally. The research consisted of quasi-static (QS) tests where drift-based cyclic loading reversals were used and pseudo-dynamic (PsD) tests where acceleration intensity-based loading was used. Twelve 1/3-scaled RC frames were built and tested as bare and infilled control frames, and as cross-braced and cross diamond-braced retrofitted specimens. Significant findings were noted while comparing the QS and PsD tests. The maximum restoring force and drift couples that were obtained from PsD tests showed a close behavior pattern, regardless of the level of inertial masses, when compared with QS tests. The energy dissipation capacity of the specimens that was obtained from PsD test resulted somewhat less than the one tested with QS for the same level of damage. The performance of the retrofitted frames that was obtained from the experimental study was evaluated with code-specified performance limits. Accordingly, it was concluded that the cross diamond-bracing scheme is an effective retrofitting technique that brings the bare frame from collapse prevention (CP) to life safety (LS) performance levels. Finally, analytical predictions as per FEMA 356 guideline were performed and good agreement was obtained with experimental results.