Torsion Experiment and Cracking-Torque Formulas of Prestressed Concrete Beams

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Title: Torsion Experiment and Cracking-Torque Formulas of Prestressed Concrete Beams

Author(s): Chyuan-Hwan Jeng and Min Chao

Publication: Structural Journal

Volume: 115

Issue: 5

Appears on pages(s): 1267-1278

Keywords: angle of twist; beam; cracking; formula; prestressed concrete; small deformation measurement; softened membrane model; torsion

Date: 9/1/2018

Abstract:
Previous torsion experiments on prestressed concrete (PC) beams have various limitations. A new experimental project was therefore conducted to test seven PC beam specimens under pure torsion. This new torsion test of PC beams achieved accurate measurement of small twists before and around cracking, and improved other aspects, including precise measurement of prestressing forces and prestress transfer. The test also enabled assessment of relatively large specimens with medium to high prestress levels and high concrete strengths. Experimental results from seven specimens are presented in this paper. The experimental values of cracking torque Tcr for the seven specimens, and for another 12 specimens from a previous experiment, are compared with the Tcr values calculated using a recently developed rational formula for reinforced concrete. Using these comparisons, a new Tcr formula for PC beams with concentrated or distributed tendons is proposed, which accurately predicts the cracking torques of the 19 specimens.