ACI 445.1R-12: Report on Torsion in Structural Concrete by Joint ACI-ASCE Committee 445

By Joint ACI-ASCE Committee 445

A transparent figuring out of the consequences of torsion on concrete contributors is vital to the secure, most economical layout of bolstered and prestressed concrete individuals. This file starts with a short and systematic precis of the 180-year background of torsion of structural concrete participants, new and up to date theories and their functions, and a historic evaluation outlining the improvement of analysis on torsion of structural concrete contributors. historic theories and truss types comprise classical theories of Navier, Saint-Venant, and Bredt; the three-d (3-D) area truss of Rausch; the equilibrium (plasticity) truss version of Nielson in addition to Lampert and Thürlimann; the compression box conception (CFT) by means of Collins and Mitchell; and the softened truss version (STM) by means of Hsu and Mo.

This file emphasizes that it really is necessary to the research of torsion in strengthened concrete that individuals 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 document bargains with layout matters, together with compatibility torsion, spandrel beams, torsional restrict layout, open sections, and measurement effects.

The ultimate chapters are dedicated to the detailing necessities of transverse and longitudinal reinforcement in torsional participants with designated, step by step layout examples for 2 beams lower than torsion utilizing ACI (ACI 318-11), eu (EC2-04), and Canadian criteria organization (CSA-A23.3-04) criteria. layout examples are given to demonstrate the stairs occupied with torsion layout. layout instance 1 is an oblong strengthened concrete beam below natural torsion, and layout instance 2 is a prestressed concrete girder less than mixed torsion, shear, and flexure.

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Extra resources for ACI 445.1R-12: Report on Torsion in Structural Concrete

Sample text

Fig. 2—Normalized T-M interaction curves for members without transverse reinforcement. 2 Members without transverse reinforcement—The T-M interaction in members containing only longitudinal reinforcement has limited practical importance, attracting a significant amount of experimental research, mainly due to its importance in understanding the behavior of members with transverse reinforcement. Behavior and ultimate strength of these members is significantly influenced by the shape of the beam cross section, the amount and distribution of the longitudinal reinforcement, and the T-M ratio (Zia 1970).

4b. Alternatively, the slab could reach its maximum load strength and redistribution could occur before reinforcement in the spandrel beam yields (Collins and Lampert 1973; Pantazopoulou and Moehle 1990). This redistribution could result in less torsion on the spandrel beam than that computed from elastic analysis; and 2. A torsional plastic hinge could form at a location across the spandrel beam axis, resulting in redistribution of torsion along the spandrel beam axis. 1R-12) 41 Fig. 4b—Idealization of spandrel beam under lateral sway (Pantazopoulou and Moehle 1990).

These two specimens closely matched the design assumption of 52 percent torsional redistribution. Specimens A5 and B3 were designed for 100 percent or complete torsion redistribution, as implied in ACI 318 commentary. As shown in Fig. 1b, torsion resisted at the joint stayed constant after cracking occurred. After cracking, the load increased significantly, almost doubling, at the same torsion value until failure. Failure occurred at a load far below design strength, indicating that the design assumption for torsion redistribution was invalid.

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