THEORY OF OPEN THIN-WALLED COMPOSITE AND PRESTRESSED BEAMS

Composite and prestressed beams having open thin-walled cross-sections involving concrete as an aging linear viscoelastic material, prestressing steel with relaxation property, and two other steel members as elastic materials are considered. The expressions for stresses and generalized displacements referring to any given open thin-walled composite cross-section and to any compliance function of concrete are developed without mathematical neglects. In the framework of the theory of composite and prestressed open thin-walled beams there exists only one approximate solution based on the approximate algebraic stress-strain relation for concrete where the prestressing steel is introduced as an elastic material. The exact theory is significant because on the basis of it is possible to create approximate calculating methods and because we can verify whether approximate methods are sufficiently accurate for the engineering practice.