Strengthening of reinforced concrete columns incorporating different configurations of stainless-steel plates

Reinforced concrete columns may need to be strengthened to support additional load arising from structural upgrades of existing structures or for retrofitting purposes. There is an increasing demand for sustainable and durable construction materials and techniques for strengthening and retrofitting purposes. Existing studies proposed additional jacketing using steel tubes or fiber-reinforced polymer (FRP). However, steel tubes can corrode when exposed to harsh environments whereas jacketing using FRP is very expensive. This study proposes innovative strengthening techniques using exterior bonding of stainless-steel plates (SSP) strips. SSP offers higher strength and corrosion resistance compared to steel and FRP materials. This paper presents an experimental and numerical study on strengthening reinforced concrete columns by innovative exterior bonding of SSP strips. A total of nine reinforced concrete column specimens are experimentally tested under axial compression loading to failure. The columns are strengthened using two different innovative techniques namely bonding stainless-steel plates to the exterior of the columns in flat as well as spirally wrapped around the columns. The cracking load, ultimate load and energy absorption capacity of the strengthened columns are found to be increased within a range of 45%− 162%, 26%− 112% and 34%− 190%, respectively when compared to the unstrengthened control column. The spacing of the SSP significantly effects the performance of strengthened columns. The ultimate load of the columns with reduced spacing increased as high as 44.9%. Additionally, employing a continuous full-height stainless steel spiral sheet yielded the most significant ultimate strength gains, calculated as high as 112% compared to the unstrengthened column although this led to an increase in the cost of the columns. A nonlinear finite element model (FEM) is also performed of the tested columns and validated the numerical prediction against the test results. The FEM is found to accurately predict the performance of such a column experimentally observed. This study provides crucial knowledge to understand the behavior of such a column and provides numerical tools for design engineers.