Torsional Analysis Methods for Perforated Cores

Several continuum methods for torsional analysis of slender perforated cores are described. First, the open section torsion‐bending theory, which neglects shear deformations, is described. It is then modified to consider shear deformations that become important with increasing lintel stiffness. To avoid the warping incompatibility, of the open section theory when applied to rigid lintel cores, a simple closed box torsion‐bending theory follows. Then an adaptation of the Umansky‐Benscoter theory is presented. Finally, the alternating closed box‐open section model is described. These methods are compared with experimental data, finite element analysis, and the wide column frame analogy. It is concluded that the Umansky‐Benscoter theory offers the most realistic modeling for relatively rigid lintel cores for which Bredt's formula becomes a simple alternative with increasing lintel stiffness. The open section theory, due to its simplicity, is adequate for more flexible systems.