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Title: Alternative Design Procedures for Torsion in ACI 318-19: A Comparative Study

Author(s): Allan Kuan, Edvard P.G. Bruun, Evan C. Bentz, and Michael P. Collins

Publication: Symposium Paper

Volume: 344


Appears on pages(s): 64-91

Keywords: reinforced concrete; prestressed concrete; torsion; design codes; shear; moment

DOI: 10.14359/51728291

Date: 10/1/2020

Although the torsion design procedures in ACI 318-19 are simple and broadly applicable, the resulting designs tend to be conservative. To address this, clause in ACI 318-19 permits the use of an alternative design procedure when designing members with an aspect ratio ≥ 3 for torsion, provided that the alternative procedure has been shown to agree with the results of comprehensive tests. This paper evaluates and compares the torsion design procedures in CSA A23.3:19 and the PCI Design Handbook 8th edition with those in ACI 318-19. Each of the three methods are found to show good agreement with 282 tests found in the literature. A comparison of the three concludes that the designs obtained using the ACI method generally require the most reinforcement. More economical designs for members subjected to relatively low and high torques can be obtained by using the PCI and CSA methods respectively. A design example of a spandrel beam using the three methods is presented, and then further conclusions are stated to guide practicing engineers on the relative strengths and weaknesses of each procedure.