STRENGTH IN SHEAR OF CONCRETE BEAMS WITH EXPOSED REINFORCEMENT

Repairs to concrete beams suffering from chloride-induced corrosion of reinforcement usually necessitate breaking out concrete around the reinforcement. Exposed reinforcement cannot act compositely with the remainder of the member, and behaviour of a beam under load is altered. Normal assumptions of section behaviour no longer hold true, and the usual code of practice procedures for evaluation of section strength are no longer directly applicable. This Paper presents results of a study to evaluate the shear strength of beams with a part of the longitudinal reinforcement exposed over varying portions of the span. A method of analysis, based on existing semi-empirical rules in BS 8110, is proposed to take account of a contribution from exposed bars. The analysis suggests that shear strength is increased when reinforcement is exposed in all but the most lightly reinforced sections. Details of a short series of laboratory tests are reported, and the method is shown to provide a reasonable if sometimes conservative estimate of strength. The findings offer potential savings by providing a more accurate method for assessment of the load carrying capacity of reinforced concrete beams weakened by the removal of concrete around the tension reinforcement while under structural repair.