The American Concrete Institute (ACI) has released a paper called Torsion Experiment and Cracking-Torque Formulas of Prestressed Concrete Beams.
The paper, written by Chyuan-Hwan Jeng and Min Chao, is based on a test of seven prestressed concrete (PC) beam specimens under pure torsion.
ACI says the torsion test of PC beams achieved an accurate measurement of small twists before and around cracking and improved the precise measurement of prestressing forces and prestress transfer. Also, the experiment enabled the assessment of relatively large specimens with medium to high prestress levels and high concrete strengths. This paper includes experimental results from seven specimens.
According to ACI: “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.”
A new Tcr formula for PC beams with concentrated or distributed tendons was proposed through using these comparisons, which accurately predicts the cracking torques of the 19 specimens.
