Date of Award

1-1-2010

Document Type

Campus Access Thesis

Department

Civil and Environmental Engineering

First Advisor

Paul Ziehl

Abstract

A lateral cyclic loading test has been completed involving four prestressed concrete pile specimens embedded into cast in-place (CIP) reinforced concrete bent-caps. The study was conducted to determine the moment capacity of the piles which is significantly affected by the slipping stress of prestressing strands. In general the ACI 318 Eqn. (12-4) is used to calculate the development length and slipping stress of prestressing strands, yet the validity of this equation for strands in confined sections is not proven. The piles used were 18 in. (457 mm) square x 18 ft (5.5 m) long and were plainly embedded into the bent-cap to depths of 18 in. (457 mm) and 26 in. (660 mm). Analytical models were created in which the slipping stress of the strands was calculated using ACI code equation for development length. In all cases the connection achieved more moment than expected due to the confining stress produced from the bent-cap which tends to decrease the development length of the strands. A modified equation that accounts for the beneficial effect of concrete confinement due to shrinkage is introduced.

Experimental data from a research completed in 1992 was used to validate the proposed equation. Analytical models were created in which the slipping stress values were calculated using the proposed equation, the current ACI code equation, and the experimental values. Generally, the proposed equation has a better match with the experimental results than the ACI code equation.

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