Title: Ledge behavior and strength of long-span L-shaped beams
Date Published: March-April 2018 
Volume: 63 
Issue: 2
Page Numbers: 50-66
Authors: Mohamed K. Nafadi, Gregory W. Lucier, Sami Rizkalla, Paul Zia, and Gary J. Klein
https://doi.org/10.15554/pcij63.2-01

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Abstract

The ledge design procedure in the seventh edition of the PCI Design Handbook: Precast and Prestressed Concrete has been called into question by several engineers and researchers since 1985. Specifically, the ledge punching-shear capacities predicted by the PCI procedure overestimate the failure loads observed in several previous laboratory tests and analytical studies. This paper presents the results of the second phase of an extensive experimental program conducted on nine fullscale, long-span, L-shaped beams with ledge heights from 8 to 18 in. (200 to 450 mm). The main objectives of this study were to investigate the effects on ledge capacity of several significant parameters, such as global stress, prestressing, ledge height, and concrete strength. In addition, the study also investigated the efficiency of selected special reinforcement details. The experimental results demonstrated that increasing the global stress significantly reduces ledge capacity, while the use of prestressing increases the capacity. The research also demonstrated that concentrating the ledge reinforcement at the load location can significantly increase the ledge capacity, offering a practical design alternative for carrying heavy loads.

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