Seismic Strengthening of Concrete Columns by Ultrahigh-Performance Fiber-Reinforced Concrete Jacketing

This paper presents the structural performance of jacketed concrete columns subjected to cyclic lateral loading using ultrahigh-performance fiber-reinforced concrete (UHPFRC) with various advantages as construction materials of high strength and durability with self-compacting. The UHPFRC jacketing with/without textile reinforcement for concrete columns for the seismic retrofitting demonstrates its strengthening efficiency and reduction of jacket thickness through the experimental program in this study. Especially, textile-reinforced UHPFRC (TR-UHPFRC) jacketing has enhanced ductility compared with that of UHPFRC jacketing by changing critical failure crack patterns in jackets. The satisfactory interface shear strength between UHPFRC jackets and substrate concrete of columns was confirmed by a series of slant shear test programs provided that required roughness on substrate with moisture were prepared according to current design guidelines. This study also investigates the effects of discontinuity of tension forces in jackets at the floor level of columns on shear load paths, which are intended to alleviate jacketing construction for columns in existing buildings as a member intervention technique. Shears and axial forces induced in jacketed columns under lateral loading are mainly resisted by compression forces in diagonal struts through the jacket with substrate concrete columns and are explained by arch actions for enhancement of shear strength after jacketing.