材料
Online ISSN : 1880-7488
Print ISSN : 0514-5163
ISSN-L : 0514-5163
合板の座屈的挙動に与える非対称積層, 荷重条件および支持条件の影響
増田 稔満久 崇麿
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1975 年 24 巻 264 号 p. 897-902

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To make clear the real buckling behaviour, the fundamental equations (I-21 and 22) were developed for the analysis of the finite deformation of plywood with imperfections-Eqs. 1 and 2 are the simple forms of the fundamental equation which does not include the distribution of the Young's moduli in xy-plane. The author made the computer program (in FORTRAN IV) to solve these equations by means of the non-linear finite difference method. Accuracy of the solution and the computation results-influences of the initial deflection (geometrical initial imperfection) and the distribution of the Young's moduli-were shown in the previous paper. In this paper the influence of the eccentric load on the load-deflection (L-D) curve of the plywood with simply supported four edges (Fig. 1) and the influence of the unsymmetrical lamination (Figs. 2 and 3) and the effect of the combination of the imperfections (Fig. 4) were investigated. From these figures the following conclusion is obtained: -The typical buckling occurs only in the special cases; (i) perfect plywood and perfect loading, and (ii) counterbalance of the imperfections. Therefore, the so called“buckling load”is not observed clearly in general. And the buckling behaviour disappears according as the imperfection becomes large.
The influence of initial compression on the L-D curve of the plywood under shear is also observed (Figs. 5 and 6). When the initial compression is not too large, the L-D curve resembles that of the plywood which has the same initial deflection as the deflection caused by the initial compression. So the initial compression can also be assumed one of the imperfections. The influence of the distribution pattern of the external shear load is shown in Figs. 6 and 7. The plywood whose face grain is inclined 45° to the horizontal edges (45°-plywood) is affected more than that of 90°(90°-plywood). The effect of the combination of the clamped edge (only the edge angle is fixed) and the simply supported one (roller support) is shown in Fig. 11, and this figure shows that the 45°-plywood exhibits the buckling behaviour at lower shear load than the 90°-plywood when more than one edge is clamped. The intermediate edge condition of“simply”and “clamp” can be expressed by“s”of Eq. 3. The bigger the support factor“s”becomes, the higher the L. E.B.B. (load at entering the buckling behaviour) becomes. But the L.E.B.B. of the 45°-plywood does not increase so much as that of the 90°-plywood, and“s=0.5”is nearer to the“clamp”than to the“simply”(Fig. 11).

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