Abstract
We have already examined the elastic-plastic behavior of gable typed frame against symmetrically distributed vertical loads in Part (I)〜(III) of this study. Aa the results of them, following conclusions were obtained, (1) Gable typed frame has two different kinds of failure mode, one of which is symmetrical mode against symmetrical vertical load with two plastic hinges on the both eaves, and the other is asymmetrical mode with only one plastic hinge on the forward eave. The former mode has enough ultimate strength of 1.2〜1.3 times of elastic limit load, while the latter mode has only 1.1 times at most. (2) The critical rigidity of the frame from symmetrical to asymmetrical is given by the function of relative stiffness ratio of beam to column according to its roof pitch. (3) The deterioration of bending stiffness caused by yield regions of members brings about considerablly large drop of the elastic-plastic buckling load. In this paper, we examined the elastic-plastic behavior of gable frames against asymmetrically distributed vertical loads by using the theory of part (II). As the index of eccentricity of vertical loads, we introduced γ which is determined by W_2/(W_1+W_2), where W_2 is sum of the larger part of vertical loads of the roof, and W_1 is sum of the smaller part. We analized the elastic-plastic behavior of various frames against the asymmetrical vertical loads between γ=0.5 and 1.0. As the conclusion of this paper, it was shown that the upper limit of γ which brings about symmetrical failure mode for existing usually designed gable typed frames is only 0.55, while the linear theory predicts more than 0.7, and the considerablly large drop of ultimate strength is unavoidable at the limit γ value.
