Strengthening of Shear-Critical RC Columns by High-Strength Steel-Rod Collars

Abstract

This research investigates the strengthening of shear-dominated reinforced concrete (RC) square columns using the high-strength steel-rod collars, which enhance confinement by steel rods around the column perimeter. This method is less intrusive to the existing building with infilled walls because steel rods can penetrate through the walls with minimal openings (holes) at the location of collars. In this study, one control specimen and two specimens strengthened by steel-rod collars were tested. All specimens were subjected to lateral cyclic loading along with a constant axial load. The difference between the two strengthened specimens were the spacing of steel-rod collars mounted on the columns. The spacing of steel-rod collars was 200 mm in the column specimen SC-200, while the other strengthened specimen, SC-100 has a spacing of 100 mm. The unstrengthened column failed in shear while the strengthened columns failed in flexure. In addition, the strengthened specimens failed at the higher load and ductility. Comparing to the unstrengthened column, the lateral load capacity and ductility ratio of the column SC-200 increase by 18 % and 59%, respectively. While, the lateral load and ductility ratio of SC-100 increase by 16% and 69%, respectively. Furthermore, the finite element models of all column specimens are developed using the OpenSees program. The analysis results are found in a close agreement with the experimental results.