Title: Debonding strands as an anchorage zone crack control method for pretensioned concrete bulb-tee girders
Date Published: September - October 2020
Volume: 65
Issue: 5
Page Numbers: 65 - 80
Authors: Emre Kizilarslan, Pinar Okumus, and Michael G. Oliva
https://doi.org/10.15554/pcij65.5-04

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Abstract

Bulb-tee pretensioned concrete girders are widely used for bridge construction. Cracks, however, are often observed near the anchorage zones of these girders during detensioning and can grow in size during subsequent transportation. The cracks can take various forms, including inclined web cracks, horizontal web cracks, and bottom-flange Y cracks. This study used field measurements and finite element analyses to investigate the impact of debonding on anchorage-zone cracks. Strains in reinforcing bar and concrete were measured and compared in girders with various levels of debonding during detensioning. Debonding 25% of strands in 72 in. (1829 mm) bulb-tee girders and debonding 38% of strands in 54 in. (1372 mm) bulb-tee girders led to reductions in strains of 12% and 54%, respectively. Validated nonlinear analytical models were used to determine efficient numbers and patterns of strands to debond. A linear correlation can be assumed between tensile strains in Y-crack regions and prestress multiplied by the square of the horizontal eccentricity of prestress force on one side of the bottom flange.