Benefits of using 0.7 in. (18 mm) diameter strands in precast, pretensioned girders: A parametric investigation

摘要

This paper presents a parametric study on the benefits and limitations of using 0.7 in. (18 mm) diameter strands in precast, pretensioned concrete bridge girders. A validated parametric study tool was used to design a variety of Texas bulb-tee, U, and spread box beams and AASHTO I and bulb-tee girders with 0.5, 0.6, and 0.7 in. (13, 15, and 18 mm) diameter strands using different span lengths, concrete release strengths, and transverse spacings. The results were used to evaluate the effects of using 0.7 in. strands on the quantity of prestressing steel, span capability, attainable superstructure slenderness, and allowable spacing between girders. The most noticeable benefit of 0.7 in. strands over 0.6 in. strands was found to be a reduction of up to 35% in the number of strands. However, the difference in the total weight of prestressing steel was insignificant. Increasing the release strength of concrete, at least to 7.5 ksi (52 MPa), was found to be essential to observe benefits in design aspects other than the number of strands.