Embedded through-section (ETS) technique for shear strengthening of reinforced concrete beams – Experimental and analytical study

This paper presents an experimental and analytical study about the effectiveness of the embedded through-section (ETS) technique for shear strengthening of reinforced concrete (RC) beams. The influence of the following parameters on the structural efficacy of the ETS technique was assessed by testing full-scale RC beams in a three-point bending configuration up to failure: (i) the material of the ETS bars, ribbed steel bars and sand coated carbon fibre reinforced polymer (CFRP) bars, bonded to concrete with an epoxy-based adhesive; and (ii) the inclination of the ETS bars, 90° and 45° with respect to the beams longitudinal axis. The test results confirmed the efficacy of the ETS technique: compared to the reference (unstrengthened) RC beam, the shear strength increased 47 %, 58 % and 59 % using respectively steel bars at 90°, CFRP bars at 90° and CFRP bars at 45°. In the second part of the study, the failure loads of the ETS-strengthened RC beams were predicted using analytical formulations adapted from those proposed in different design codes and guidelines for conventional shear reinforcement or strengthening systems. Relatively accurate estimates were obtained with the formulae from ACI 440–2 R and Eurocode 2; yet, the most accurate predictions were obtained with the formulae from fib Model Code 2010 considering relatively low values of the compressive field inclination (23° < θ < 28°), which is consistent with the inclination values of the main shear cracks observed in the experimental tests. • Experimental study of embedded-through section technique • Shear behaviour of RC beams strengthened according to ETS technique • Flexural tests on CFRP- and steel-ETS strengthened RC beams • ETS bars applied at 90º and 45º with regard to the beams’ axis • Analytical study comparing three different design models