Finite Element Modeling of CFRP-Strengthened Low-Strength Concrete Short Columns

Carbon fiber-reinforced polymer (CFRP) sheets and plates are now being extensively used as retrofitting/strengthening system, due to high strength, low weight, corrosion resistance, and ease and speed of application. Structures with very low-strength reinforced concrete columns, constructed during the early 1970s and 1980s, are rampant in many countries. These structures are prone to collapse during a seismic event. It is important to investigate if these low-strength concrete columns can be made safe by CFRP sheet strengthening. An experimental and numerical investigation conducted on short circular low-strength concrete column is presented. The results of this study showed that the confinement equations for concrete columns as per ACI and CSA codes give erroneous results for these columns. The CSA code equations require satisfaction of certain constrains, which are not applicable to such columns. Control specimen (unconfined specimens) results showed that both CSA and ACI equations overestimate the ultimate loads of low-strength RC columns by an order in magnitude. For CFRP-confined specimens, the ACI and CSA code equations overestimate the strength by about 13% and 24%.