Seismic retrofit of concrete-masonry-infilled steel frames with glass fiber-reinforced polymer laminates

An experimental investigation was conducted to study the effect of retrofitting unreinforced concrete masonry-infilled steel frame structures using glass fiber-reinforced polymer (GFRP) laminates. The study focuses on enhancing the in-plane seismic behavior of unreinforced masonry (URM) infill walls when subjected to displacement controlled cyclic loading. Six full-scale single-story single-bay steel frames with different infill configurations were tested. The retrofitting technique using GFRP laminates aimed at creating an engineered infill wall with a well defined failure mode and a stable postpeak behavior as well as containing the hazardous URM damage and preventing catastrophic failure. Results demonstrated the effectiveness of the GFRP laminates in preventing both shear and tension cracking by supplying the required tensile and shear strength. The GFRP laminates also increased the lateral load capacity and enhanced the postpeak behavior by stabilizing the masonry face shells and preventing their out-of-plane spalling. Supporting the face shells against out-of-plane spalling, allowed the wall to carry more in-plane loads and prevented sudden drop in the load carrying capacity.