|Title||Instrument to evaluate remaining prestress in damaged prestressed concrete bridge girders|
|Publication Type||Journal Article|
|Year of Publication||1998|
|Authors||Civjan SA, Jirsa JO, Carrasquillo RL, Fowler DA|
The decision of whether to repair or replace a damaged prestressed concrete bridge girder can be very difficult when a reliable estimate of prestress remaining in the strands is not available. A prototype instrument has been developed to estimate stress levels in exposed prestressed strands in existing members. The stress level is determined by application of a lateral force to an exposed strand and measuring the resulting displacement. The instrument was calibrated for 0.5 in. (12.7 mm) diameter seven-wire strand with exposed lengths of 7.5 to 3.75 ft (0.46 to 7. 7 4 m). It was tested to determine its accuracYt precision, and usefulness in the field. Strand forces were consistently estimated to within 7 0 percent of the actual load. The device was also utilized in the placement of strand splices and was found to be more reliable in checking induced strand tensions than the standard torque wrench method.