移動式起重機吊桿挫屈強度的有限元素分析

Buckling Load Analysis of the Crane Jib by Finite Element Method

起重機在勞工安全衛生法令中為危險性機械之一，吊桿（Jib）是起重機的重要構 件，其挫屈強度的計算，是吊桿安全荷重的基礎，各國皆訂有極為嚴格的標準。本文旨在應用有限元素法計算起重機之吊桿在最不利狀況時之挫屈負荷（bucklingload）。線性挫屈強度分析的減元法（reduced method）及部份空間法（subspace method），與非線性挫屈強度分析的結果，將與計算標準公式作比較。計算標準公式礙於微分方程式之解答，只能採簡化的模型，然有限元素方法能採較符合實際情況的模型，其結果較合理。

Cranes are one type of dangerous machineries classified by the regulations of occupational safety and health, of which one of the most important components is the jib. One major consideration in the design of a crane is calculation of the bucking load of the jib. Various specifications have been issued by different countries for the design of the crane jib. The paper deals with predicting the buckling load of the crane jib by the finite element method under the most severe conditions. Both the linear and nonlinear analysis of buckling loads for the crane jib are conducted. The numerical results obtained from the finite element analyses are compared with those from the specifications for crane structures. The specifications are based on the simplified model, while the finite element model can accommodate the variations in geometry and the nonlinear features of the structures, the latter appears to be more practical.