CRITICAL SOFTENING OF HINGES IN INDETERMINATE BEAMS AND PORTAL FRAMES

Softening behaviour is assumed to occur over a finite hinge length at any point in a continuous beam or portal frame. Formulae are derived for the critical softening parameter for a first- formed hinge corresponding to which the structure as a whole cannot sustain increased load. "Soft points" at which a (sub CR) is a minimum may be found for each member. Analytical values for a (sub CR) are verified in an example where softening occurs in the first formed hinge of a portal frame. (Author/TRRL)