Tests were conducted on four 203 × 406 × 5490 mm (8 × 16 × 216 in.) steel prestressed beams strengthened by exterior CFRP post-tensioned tendons. The beams were each prestressed with either one or two 13 mm (0.5 in.), 7 wire steel prestressing strand and tested under four point loading. Exterior post-tensioning for strengthening was provided by two 8 mm (0.32 in.) diameter CFRP (Leadline) tendons, harped 4.8 degrees at each of two points. Effective steel prestress of the beams varied from 985 to 1130 MPa (143 to 164 ksi). For each type of beam (with one or two steel strands), one "control" beam and beams strengthened by exterior CFRP tendons were tested. The post-tensioning stress in the CFRP tendons varied from 1240 to 1500 MPa (180 to 218 ksi). The average strength increase of CFRP strengthened members was 115% for the beams with single steel strands and 46% for beams with double steel strands. Midspan deflections at ultimate load for strengthened beams were approximately 60% of the corresponding control beam deflection.rnA numerical analysis is presented that models the post-tensioning as exterior applied forces. A layered cross-sectional analysis is used to determine curvatures for individual segments along the beam, and the curvatures are integrated over the beam span length to compute deflections. An iterative approach is used to ensure the exterior tendon force used in computing deflections equals the tendon force expected due to displacement at the harping points.
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