Design Model for Continuous Composite Beams with Web Openings

Continuous composite beams can be designed according to the plastic hinge theory. In that case in a statically indeterminate system plastic hinges are formed one after the other until a kinematic mechanism is generated (ultimate limit state). In the case of continuous beams with web openings, areas of plastic deformation can be generated in the area near the opening itself. This means that under certain circumstances local plastic moment hinges are formed in the corners of the opening. All these local hinges together result in a global plastic hinge for shear forces. Up to now the structural and deformation behaviour of such a hinge was not clarified if it acts as a global mechanism with one degree of freedom. The necessary conditions to generate such a plastic hinge for shear forces were also not clear. At Kaiserslautern a research project, that examined such beams, has been completed. Its results and a design model are described in this paper.