DETERMINATION OF ROTATION CAPACITY REQUIREMENTS FOR STEEL AND COMPOSITE BEAMS

A method is presented for the calculation of the necessary joint rotations to permit the use of moment redistribution as the basis for the design of semi-continuous steel and composite frames. The method is based on the use of moment-curvature relationships obtained from consideration of the basic steel and concrete stress-strain curves. It simplifies the determination of the support rotations required for specific percentage redistributions of support moments to the mid-span cross-section as used in EC4 by considering these to be composed of an elastic and a plastic part. Several different load cases are considered, together with a wide range of beam properties, The resulting calculation method, which uses only formulae and graphs, is illustrated by an example.