Behaviour of continuous reinforced concrete beams during the patch repair process

Abstract

The main cause of deterioration of reinforced concrete is chloride-induced corrosion of reinforcement. Repairs may require that contaminated concrete around the reinforcement be broken out and replaced. The pattern of strains will change when bond is lost and if the beam carries load during the repair process, the pattern of strains will differ from those in the “as new” condition. This study aims to develop analytical procedures to represent structural behaviour and to assess the circumstances in which changes in behaviour are significant. The testing programme embraced a range of parameters including the length and position of breakout and the load carried by the structure during casting of the repair. Various top and bottom reinforcement areas were chosen to investigate the influence of the exposed steel area and the difference between the elastic and plastic bending moment diagrams for the “fully bonded” specimen. In a statically indeterminate structure, breakout of concrete over a portion of a span causes loss of section stiffness in that region and a consequent transfer of moment to other parts of the structure. However, test and numerical data show that the flexural strength of a member with exposed reinforcement was primarily influenced by the increase in stress at the breakout location. Flexural strength and ductility of the repaired member are more likely to be reduced if the member carries load during repair as this increase in stress remains “locked into” the member.