Reliability of bond measuring devices in pretensioned prestressed concrete

One of the major deficiencies in prestressed concrete bond research is the absence of a standard method for determining bond strength. This makes comparisons between different investigations and bond values difficult. In this study, the concrete strains were measured through the utilization of demec points at the outer surface of the concrete and strand strains were measured by using resistance strain gauges that were mounted on individual wires of the seven-wire strand. Each method has its own merits and demerits. This paper presents a summary of an experimental investigation that was conducted to determine the reliability of bond measuring devices in pretensioned prestressed concrete. Use of resistance strain gauges in measurements provides instantaneous results as opposed to the time consuming nature of the demec gauge measurements. In this experimental programme an attempt has been made to ascertain the reliability of these measurements by applying both.