Title: Experimental investigation of multiple-strand lifting loops
Date Published: May - June 2024
Volume: 69
Issue: 3
Page Numbers: 74 - 88
Authors: Sandip Chhetri and Rachel Chicchi Cross
https://doi.org/10.15554/pcij69.3-03
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Abstract
An experimental investigation of 28 tests was conducted to determine the load-carrying capacity of 0.6 in. (15.2 mm) diameter prestressing strand lifting loops. The parameters studied were number of strands in a loop (1, 2, 3, or 4), lifting device (shackle or hook), vertical offset or use of a crushed sleeve, projection of loop from the top of the concrete, and splaying of strand legs. Strand rupture was the primary failure mode, though pullout and side-face blowout became prominent modes in multiple-strand cases. A uniform bond stress of 100 psi (690 kPa) can be used to determine a safe load. Multipliers of 1.9, 2.8, and 3.3 were determined for double-, triple-, and quadruple-strand loops. Hooks decreased the loop’s capacity by approximately 12% relative to a 2.4 in. (61 mm) diameter pin. A vertical offset of 1 in. (25.4 mm) decreased the loop’s capacity by approximately 42%. Efforts should be made to ensure even loading of the multiple strands within a loop.