End-Region Behavior of Pretensioned I-Girders Employing 0.7 in. (17.8 mm) Strands

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Title: End-Region Behavior of Pretensioned I-Girders Employing 0.7 in. (17.8 mm) Strands

Author(s): J. Salazar, H. Yousefpour, R. Alirezaei Abyaneh, H. Kim, A. Katz, T. Hrynyk, and O. Bayrak

Publication: Structural Journal

Volume: 115

Issue: 01

Appears on pages(s): 91-102

Keywords: 0.7 in. strands; bursting stresses; end-region cracking; pretensioned; spalling stresses; splitting resistance; transfer length

Date: 1/1/2018

Abstract:
This paper presents an experimental study on transfer length, end-region cracking, and transverse end-region stresses in pretensioned concrete I-girders fabricated using 0.7 in. (17.8 mm) diameter strands on a 2 x 2 in. (51 x 51 mm) grid. The full-scale specimens consisted of two Tx46 and two Tx70 girders that were fabricated in a controlled laboratory environment using different strand patterns and concrete release strengths. The detailing for mild-steel reinforcement was done according to the current practice in Texas for girders with smaller-diameter strands. The measured 24-hour transfer lengths from the specimens exceeded estimates by both AASHTO LRFD and ACI 318-14 provisions. The observed crack widths in the specimens within 28 days after prestress transfer were generally limited to 0.007 in. (0.18 mm), indicating satisfactory performance for exposure to deicing chemicals according to ACI 224R guidelines. However, noticeably greater transverse forces were observed in the end regions of the specimens compared to the resistance required by AASHTO LRFD specifications.