Transfer and Development Length of 15-mm Strand in High Performance Concrete Girders

Abstract

The purpose of this experimental research program was to verify that the transfer and development length of 15-mm (0.6-in.) diameter prestressing strand were less than calculated by the current American Association of State Highway and Transportation Officials Specifications when used in high performance concrete bridge girders. The scope was limited to testing four AASHTO Type II girders, two made from 70 MPa and two from 100 MPa design strength concretes. Transfer length was determined by measuring strand end slip and concrete surface strain. Development length was determined by performing eight flexure tests with varying embedment lengths. Transfer length averaged 447 mm (17.6 in.) and 371 mm (14.6 in.) for the 70 and 100 MPa concretes, respectively. The development length was found to be 2032 mm (80 in.). These values were less than those given by the current AASHTO and ACI code provisions; therefore it is recommended that current code provisions be used for pretensioned concrete girders with strengths up to 100 MPa.