By Joint ACI-ASCE Committee 445

Transparent realizing of the results of torsion on concrete contributors is key to the secure, low-cost layout of strengthened and prestressed concrete participants. This file starts with a quick and systematic precis of the 180-year heritage of torsion of structural concrete participants, new and up-to-date theories and their functions, and a old evaluate outlining the improvement of study on torsion of structural concrete individuals. ancient theories and truss types comprise classical theories of Navier, Saint-Venant, and Bredt; the third-dimensional (3-D) house truss of Rausch; the equilibrium (plasticity) truss version of Nielson in addition to Lampert and Thürlimann; the compression box idea (CFT) via Collins and Mitchell; and the softened truss version (STM) by way of Hsu and Mo.

This record emphasizes that it truly is necessary to the research of torsion in strengthened concrete that contributors may still: 1) fulfill the equilibrium (Mohr’s pressure circle); 2) obey the compatibility (Mohr’s pressure circle); and three) determine the constitutive relationships of fabrics similar to the “softened” stress-strain courting of concrete and “smeared” stress-strain courting of metal bars. The habit of individuals subjected to torsion mixed with bending second, axial load, and shear is mentioned. This record bargains with layout concerns, together with compatibility torsion, spandrel beams, torsional restrict layout, open sections, and measurement results.

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Additional info for ACI 445.1R-12 - Report on Torsion in Structural Concrete

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3a shows that the presence of torsional moment reduces shear strength, especially if the torque is more than 25 percent of pure torsional strength. The amount of transverse reinforcement is considered the main factor affecting the shape of the curve. Based on an experimental testing program, Klus (1968) suggested a bilinear interaction curve as shown in Fig. 3b. The theoretical model and the experimental results of Ewida and McMullen (1981) showed the amount of reinforcement has a considerable effect on the interaction curve.

Fig. 1—Shearing stress due to shear, torsion, and combined shear and torsion. action curve. ACI code equations were used to calculate To and Mo for use in Elfgren’s model. 3h(a) shows that for this test series, ACI 318-11 is unconservative in its calculation of To, which affects the calculation of the interaction curves. Fig. 3g—Normalized T-M interaction curves for members with unsymmetrical longitudinal reinforcement (Lampert and Collins 1972). Fig. 3h—Interaction curves predicted by combinedaction STM and Elfgren Model for McMullen and Warwaruk (1967).

Research on the T-M interaction in members containing only longitudinal reinforcement is mainly experimental. 2 shows examples of the interaction curves recommended by various researchers. For square and rectangular sections, Kemp et al. (1961) and Hsu (1968a) independently suggested the trilinear interaction. Victor and Ferguson (1968) suggested a similar trilinear interaction for L-sections, and a square interaction for T-beams. Lim and Mirza (1968) also proposed a square interaction curve for T-beams.

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