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Shear design of pile caps and other members without transverse reinforcement Zhou, Zongyu


This thesis deals with the shear design of structural concrete members without trans verse reinforcement. The three major parts of this study are the transverse splitting of compression struts confined by plain concrete, the development of a rational design procedure for deep pile caps, as well as a general study of the shear transfer mechanisms of concrete beams. Three-dimensional compression struts that are unreinforced and confined by plain concrete, as occur in deep pile caps, were studied both analytically and experimentally. Based on the study results, bearing stress limits are proposed to prevent compression struts from transverse splitting. The maximum bearing stress depends on the amount of confinement, as well as the aspect ratio (height to width) of the compression strut. The proposed bearing stress limit was incorporated into a strut-and-tie model to develop a rational design procedure for deep pile caps. Two methods are proposed. The first method is a direct extension of two-dimensional strut-and-tie models used for deep beams. The second method is presented in a more traditional form in which “flexural design” and “shear design” are separated. The shear design is accomplished by limiting the bearing stress at the columns and the piles. The first method is more appropriate for analysis, while the second method is more appropriate for design. The rationality and accuracy of the proposed methods are demonstrated by the comparison with previous test results. In the final part of this study, the influence of bond between concrete and longitudinal reinforcement upon the load transfer mechanism of both deep members and slender members without stirrups are investigated. An interpretation of an important shear failure mechanism is presented.

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