Prediction of the behaviour of RC beams with exposed reinforcement

The paper reports details of a fairly simple theoretical model for estimating the flexural ultimate load of reinforced concrete beam under two-point loading in which the main reinforcement over part of the span is fully exposed in a symmetrical fashion about the mid-span in the course of the patch repair process prior to the application of the repair materials. Encouraging correlations have been found between the theoretical predictions and large-scale experimental data reported by others, which covered a wide range of design parameters. Theoretical numerical results throw some light on the perhaps initially puzzling experimental observations reported previously that the ultimate loads of beams with exposed reinforcement can increase significantly if nominal top steel (in the form of, for example, 2 × 6 mm dia. bars), such as is invariably used for holding stirrups in place, is used. Numerical results are presented that show the influence of various parameters (concrete cube strength, length of exposed main reinforcement, depth of removal of concrete, etc.) on the ultimate loud-bearing capacity of beams with exposed main reinforcement.