Robert Barnes

Experimental Assessment of Factors Affecting Transfer Length

Transfer lengths (TLs) were measured for 184 transfer zones in 36 plant-cast AASHTO Type I girders prestressed by 0.6 in. diameter strands at 2 in. spacing. The influence of concrete compressive strengths ranging from 5,700-14,700 psi (39-101 MPa) is studied. To represent the full range of strand surface conditions found in practice, the prestressing strand featured either a bright mill finish or a rusted surface condition. Several methods of prestress release were employed. Results indicate that TL decreases with increasing concrete strength. TLs increased significantly during the first weeks after prestress release. Prestress release method had little effect on the TL of bright strands in high-strength concrete. Sudden prestress release, however, resulted in significant increases in rusted strand TLs.