Behavior of simple-span reinforced concrete beams locally strengthened with external tendons

Abstract

An investigation of simple-span reinforced concrete beams strengthened by external tendons that are anchored at intraspan locations is carried out and reported herein. It is shown analytically that anchoring the tendons at locations less than a critical distance from the beam end would result in the strengthened beams performing satisfactorily in terms of ultimate load-carrying capacity. The critical distance depends on the loading configuration and the desired strength enhancement. To substantiate the analytical results, five understrength reinforced concrete beams were strengthened with steel or carbon fiber-reinforced polymer (FRP) tendons and tested to failure under third-point loading. The test results indicate that it is possible to locally strengthen the beam by anchoring the tendons at intraspan locations without compromising the deflection and cracking behavior, in addition to ultimate load behavior. The process leads to shorter, and hence more economical, use of external tendons, as well as minimizing second-order effects due to varying tendon eccentricities under load. The same results were obtained for beams strengthened with external steel or FRP tendons.