Subassemblage Technique for Asymmetric Structures

During the past decade methods have been developed to predict the complete load-deflection relationships for unbraced multistory frames. The subassemblage method consists of a story-by-story investigation of the frame, assuming that points of inflection occur in the columns at midheight. The subassemblage method is able to account for the gradual deterioration of the frame due to the formation of plastic hinges in the beams and columns and the secondary moments produced by the gravity loads acting on the deformed structure. If the floor diaphragms are relatively rigid in their planes, the subassemblage technique can be easily extended to assess the behavior of structures free to deform torsionally under the action of the applied loads. Rigid body motion of the floor diaphragm in each story is enforced on the frames composing the structure. The deformations are then adjusted at each stage so that equilibrium of forces and torsional moments are satisfied. By increasing the deformations, the complete load-deformation curve may be traced.