Shear Strength of Post-Tensioned Daps in Prestressed Concrete Beams

by Ali A. Hamoudi, Asst. Prof. of Civ. Engrg.; Univ. of Baghdad, Baghdad, Iraq,
Michael K. S. Phang, (M.ASCE), Engrg. Specialist and Proj. Engr.; Van Houten Assocs., Inc., New York, NY,

Serial Information: Journal of the Structural Division, 1974, Vol. 100, Issue 12, Pg. 2403-2418

Document Type: Journal Paper


In prestressed concrete beams with dapped ends, inclined shear cracks appear frequently at early stages of loading. A theoretical solution based on elasticity methods was formulated to represent the onset of failure at the dapped regions. The solution gave a quantitative prediction of the critical tensile stresses at a point close to and very near the dap root. Experiments were conducted on six prototype prestressed concrete T-beams. The beams were pretensioned longitudinally and were provided with post-tensioned, high-strength, steel web reinforcement. The variables included: (1) geometry of the dapped ends; (2) type of web reinforcement in dapped regions; (3) ratio of shear span to depth of beam; and (4) prestress level. The results indicated that shear strength of prestressed concrete beams can be predicted with reasonable accuracy, and that dapped regions can be prestressed with inclined high-strength steel bars to control shear cracking at the working load.

Subject Headings: Shear strength | Concrete beams | High-strength steel | Structural strength | Tension | Prestressing | Prestressed concrete | Cracking

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