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A simple unbonded-type shear strengthening technique for reinforced concrete beams using wire rope units is presented. Ten two-span reinforced concrete T-beams externally strengthened with wire rope units and an unstrengthened control beam were tested to failure to explore the significance and shortcomings of the developed unbonded-type shear strengthening technique. The main parameters investigated were the type, amount and prestressing force of wire rope units. All beams tested failed owing to significant diagonal cracks within the interior shear span. However, beams strengthened with closed type wire rope units exhibited more ductile failure than the unstrengthened, control beam or those strengthened with U-type wire rope units. The diagonal cracking load and ultimate shear capacity of beams with closed-type wire rope units were linearly increased with the increase of vertical confinement stresses in concrete owing to the prestressing force in wire rope units, while those of beams with U-type wire rope units were little influenced. It was also observed that average stresses in closed-type wire ropes crossing diagonal cracks at ultimate strength of beams tested were far much higher than those in U-type wire rope units, showing better utilization in case of closedtype wire ropes. The shear capacity of beams with closed-type wire rope units is conservatively predicted using the equations of ACI 318-05 for shear modified to account for the external wire rope units. A numerical formula based on the upper bound analysis of the plasticity theory is also developed to assess the load capacity of continuous T-beams strengthened with wire rope units.Comparisons between measured and predicted shear capacities showed that the coefficient of variation obtained from the mechanism analysis is less than that from the modified ACI 318-05 equations. In addition, the predictions by the mechanism analysis for beams with closed-type wire rope units are in good agreement with test results, regardless of the value of stresses used for the calculation of energy dissipated in wire ropes.

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