tailieunhanh - design of wood aircraft structures phần 9

Tôi không có đầy đủ ANC-19 trong PDF nhưng đây là một số thông tin từ ANC-19 liên quan đến "Yêu cầu đối với gỗ trong bộ phận cụ thể". Ba tài liệu PDF có thể được sử dụng để xác định kích thước và vị trí của những con số đăng ký lớn trên cánh. | b I u I L L Ỵ L L L L c . VQ V _ conform to the or values of the fuselage section as applicable giving a distribution of shear forces of the type shown in figure 3-27 A or B. Some designers take into account the fact that due to concentration of load where the frame is attached to the wing the shear is carried mostly by the adjacent fuselage skin and the shear resistance of the skin is reduced arbitrarily somewhat in proportion to its distance from the point of concentrated load application. This would yield a shear force distribution of the type shown in figure 3-27 c. In such cases the fuselage skin should also be checked for the high stresses indicated. The ordinary method of frame analysis is strictly applicable to frames the deflections of which are not restricted by the fuselage skin. Actually the frame deflections may become quite pronounced and the outward deflections are resisted by double-curvature effects in the fuselage skin or by the support of adjacent frames. This action of the skin is equivalent to introduction of inward-acting loads resisting the frame bending and hence to a reduction of frame stresses to smaller values than those indicated by an analysis based upon shear distributions as described. The present development of the theory does not indicate quantitatively just what allowance can be made for this reduction of stresses. It is recommended therefore that the frame analysis be conducted by the methods similar to the ones indicated. Where relatively deep frames are used the moments induced by the wing deflections may become important and should therefore be analyzed. . Intermediate frames. Intermediate frames are provided to preserve the shape of the fuselage structure to reduce the column length of the stiffeners and to prevent failure of the structure due to general instability. They are subjected to several types of loading such as those due to tension fields in the skin to fuselage bending to transfer of shear to the fuselage .