Crack Width Prediction for Ledges in Inverted ‘T’ Bent Caps

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Title: Crack Width Prediction for Ledges in Inverted ‘T’ Bent Caps

Author(s): R. R. H. Zhu and T. T. C. Hsu

Publication: Special Publication

Volume: 225

Issue:

Appears on pages(s): 179-196

Keywords: bent caps; crack width; inverted-T beam; re-entrant corner; reinforced concrete

Date: 3/1/2005

Abstract:
Inverted “T” bent caps are used extensively in concrete highway bridges because they are aesthetically pleasing and offer a practical means to increase vertical clearance. The problem is that at service load unacceptable diagonal cracks frequently occur at the re-entrant corners between the cantilever ledges and the web. In order to control the diagonal cracks, an extensive three-phase investigation was carried out. The first phase was to predict the diagonal crack widths at the interior portions of the bent caps. A 2-D analytical model, called Compatibility-Aided Strut-and-Tie Model (CASTM), was developed. This model was calibrated by testing seven full-size 2-D test specimens. The second phase was to predict the diagonal crack widths at the end faces of the exterior portions of bent caps. In this phase the CASTM was extended to 3-D analysis, which was calibrated by testing ten 3-D specimens. In the third phase, two whole-wholebent-cap specimens were tested to determine the effective distribution width in the vicinity of an interior applied load on the ledge. Crack control methods for the interior spans and the exterior end faces were recommended.