Effective anchorage stress of prestressed tendons in PC girders under varying tensioning sequences

In current design codes, the standardized anchorage stress of prestressed tendons in concrete girders is uniform, which presents a notable challenge in accurately assessing the effective anchorage stress of girders with varying span lengths. This study investigates the impact of prestressed tendons’ span length and tensioning sequences on effective anchorage stress in small-box girders (20 m, 25 m, 30 m) and 40 m T-shaped girders. Comprehensive theoretical approaches for computing the effective anchorage stress of the tendons, accounting for stress losses due to conduit friction, anchor deformation, rebar relaxation, concrete, and joint compression, are presented. The calculated results for prestressed concrete (PC) girders with typical span lengths and cross-sections demonstrate that girder length and tensioning sequence influence the effective anchorage stress of prestressed tendons. The currently recommended standardized effective anchorage stress of 1280 MPa in existing codes, derived solely from a designated length and anchorage retraction, proves inadequate for PC girders of varying lengths. Based on theoretical and numerical findings, refined effective anchorage stress of 1237 MPa, 1244 MPa, and 1251 MPa are proposed for small-box girders with span lengths of 20 m, 25 m, and 30 m, respectively, while the recommended effective anchorage stress for a T-shaped PC girder with a length of 40 m is 1251 MPa. Adoption of the evaluation method effective anchorage stress yields an improved prestressed quality passing rate ranging from 4.0% to 10.9%, thereby effectively reducing the necessity for unnecessary supplementary tensioning or excessive tensioning during on-site construction to meet project requirements.