The strength of plain, reinforced and prestressed concrete under the action of combined stresses, with particular reference to the combined bending and torsion of rectangular sections

Abstract

Summary A theory for the strength of concrete and reinforced concrete under the action of combined stresses is advanced, which combines Rankine's maximum principal stress criterion and Coulomb's internal friction criterion. Equations for the strength of plain, reinforced and prestressed concrete in combined bending and torsion are then derived. The distinct difference between primary bending and primary torsion fracture is explained by the dual character of the criterion of failure. It also accounts for the increase in the torsional strength of a reinforced concrete section resulting from the addition of bending. Prestressing delays the formation of tension cracks until the compression due to the initial prestress has been offset, and it therefore effects a very great improvement in the torsional strength of concrete.