Hybrid UHPC/NSM CFRP strips vs. traditional systems for flexural upgrading of RC beams – Experimental and FE study

Abstract

In this study, the efficacy of traditional versus innovative systems for enhancing the flexural strength of RC (reinforced concrete) beams is investigated experimentally as well as numerically. Four-point bending tests were conducted on seven RC beams. Test matrix comprised of two control and five strengthened beams. Strengthening techniques included: bonded steel plate, externally attached CFRP (carbon fiber reinforced polymer) composite, NSM (near-surface mounted) steel rebars, externally attached CFRCM (carbon fiber reinforced cementitious matrix) composite, and innovative hybrid system comprising of ultra-high performance concrete (UHPC) layer combined with NSM CFRP strips. Different strengthening systems were designed to provide approximately the same flexural strength enhancement. The performance of strengthened specimens was compared in terms of load–deflection characteristics. The peak load of the tested specimens was analytically predicted using the equations of ACI 318-19 code and ACI 440.2R-17 guidelines. Nonlinear FE (finite element) modeling was also carried out, and a comparison was conducted between the experimental and FE results showing good agreement. The validated FE models were extended for some useful parametric studies of interest.