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Title: Flexural Cracking Behavior of Partially Prestressed Pretensioned and Post-Tensioned Beams--State of the Art

Author(s): E. G. Nawy

Publication: Symposium Paper

Volume: 113


Appears on pages(s): 1-28

Keywords: beams (supports); cracking (fracturing); crack width and spacing; partial prestressing; post-tensioning; prestressed concrete; pretensioning; serviceability; tensile stress; Structural Research

Date: 4/1/1989

More prestressed beams incorporating mild steel reinforcement are built today with allowance of tension in the concrete, that is, partial prestressing. Consequently, a study of their cracking behavior and control of the crack width and distribution are significant. Available experimental data on the cracking behavior of prestressed beams is limited. Because of the importance of serviceability behavior of these elements, several experimental and analytical investigations have been undertaken and expressions proposed. Simple mathematical expressions have been developed. The proposed expressions for evaluating crack widths in partially prestressed beams at working load and overload have been developed in terms of the controlling parameters, namely, the variation in the steel reinforcement and percentage of the prestressing tendons and the nonprestressed reinforcement. The mathematical model is applied to tests on 20 simply supported pretensioned 9 ft span beams, 4 two-span continuous beams of effective 9 ft span, and 22 simply supported post-tensioned beams of 7 ft, 6 in. span. The major controlling parameters were the variation in the steel reinforcement percentage of the prestressed tendons and the nonprestressed reinforcement. The effect of concrete cover was incorporated in the value of the concrete area in tension.


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