Sadao Komatsu

Elasto-plastic analysis of orthogonally stiffened plates with initial imperfections under uniaxial compression

In general, the stiffened plates consisting of steel plate elements are unavoidably accompanied by initial imperfections such as residual stress and initial deflections, which have considerable effects on their ultimate strength. Therefore, it is needed for designing them to develop more rational method taking the ultimate strength influenced by initial imperfections into account rather than the conventional design method being on the basis of the linear elastic buckling theory. From this point of view, this study aims to evaluate rigorously the ultimate strength of orthogonally stiffened plate with initial imperfections under uniaxial in-plane compression. The elasto-plastic finite element method is applied to attain this purpose. By a happy combination of modal analytical technique and conventional finite element method, much reduction of the degree of freedom can be expected to be realized herewith. Some numerical calculations are performed by means of this rigorous method to examine the exactness of the analysis. Moreover, the numerical results are compared with the experimental ones.(a) (TRRL)

ON SHEAR LAG IN CONTINUOUS BOX GIRDER

On the basis of the sufficiently accurate approximate solutions obtained by using generalized Galerkins method, both the stress distribution and the variation of shear lag extending over the total length are investigated with respect to the continuous box girder, having the steel deck.Since it is readily seen that this phenomenon has a general tendensy to become violent at the middle supports, the practical formula for design is favorably derived with the object of determining the remarkable maximum bending stress in the vicinity of these supports.Furthermore, to make clear the relation between shear lag and the cross-sectional shape of the box girder, the ratio of the maximum bending stress to the fiber stress given by means of primary bending theory is calculated against the various proportions among the crosssectional dimensions.

ON THE PRACTICAL CALCULATION FOR BOX GIRDER BRIDGE

A method is presented for the practical calculation of box girder bridge having two main box girders. The important characteristic in such structure is, moreover, made clear.Considering on common action between sway bracing and deck in order to define its equivalent rigidity, two kinds of useful formulas corresponding to different loading conditions are introduced.According to above consideration, we can give a criterion for applying the bending torsion theory to the box girder bridge wherein the cross-sectional shape is assumed to be invariable; and then it is sufficiently concluded that general composite box girder bridge with narrow width such as King County can satisfy this condition.