Dapped Ends Research Articles

프리캐스트 게르버 U형보의 댑 전단 거동평가

프리캐스트 게르버 U형보의 댑 전단 거동평가

Validation of an Alternative Reinforcing Detail for the Dapped Ends of Prestressed Double Tees

Prestressed concrete (PC) dapped-end beams have been used in buildings and parking structures to provide an efficient and economical construction system. The re-entrant corner of a dapped-end beam develops a severe stress concentration, which makes it the weakest point of the connection. If suitable reinforcement is not provided at this location, diagonal tension cracks may propagate rapidly and failure may occur with little or no warning. Reinforcing schemes and associated methods of design, which combine simplicity of application with economy of fabrication and provide the margin of safety required by present building codes, have been developed. This paper describes the experimental validation of an alternative reinforcing detail for the dapped ends of prestressed double tees, which satisfies the requirements of the design method contained in the PCl Design Handbook, Fifth Edition.

Shear Strength of Post-Tensioned Daps in Prestressed Concrete Beams

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.