| 摘要 |
A particular arrangement of web stiffening members for the extensible and retractable telescoping sections of a crane boom assembly. A series of web stiffening members are secured to each of the side webs of a telescoping boom section, the web stiffening members being angularly displaced in a particular arrangement on each boom section to provide for reduced stress levels in the section. The web stiffening members are arranged on each side web in two series of members, the innermost stiffener of each series being reversely positioned about a reference point provided on the boom section. The reference point for the boom section corresponds to the point of changeover for shear load for the section under cantilever loading. At the defined reference point of the boom section the innermost stiffener of each series of stiffeners are angularly disposed away from each other to form a V-shaped configuration with the apex of the V directed to the lower or compression flange of each boom section and the remaining stiffeners of each group longitudinally spaced outwardly therefrom in respective parallel, spaced relation. The angular displacement of the stiffeners is derived from a formulation which provides for improved stress levels in the boom section. The formula set forth below provides, B angle for the web stiffeners when calculated to minimize the stress level in the web at a given load as follows: <IMAGE> Thus the use of the shear loading diagram for a beam under cantilever end loading combined with the formulation providing the optimum stiffener angle results in a stiffener arrangement which produces reduced stress levels in the boom section. The use of the method proposed provides two groups of web stiffeners for each side web of each boom section, arranged in parallel longitudinally spaced relation, each group angularly inclined toward the horizontal at the angle prescribed by the formulation, but reversely positioned on opposite sides of the changeover point.
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