移動式起重機全域穩定性電腦輔助分析

Computer-aided-analysis for Global Stability of Mobile Cranes

本文探討移動式起重機吊掛作業中的穩定性，首先根據國際標準及國家法規以兩個支撐點構成的傾覆線為基準計算安定度，根據計算結果，提出兩個延伸的議題，其一是當斜坡、風荷重及吊桿旋轉同時作用時，根據線性疊加的計算以組合負荷作業安全公式計算吊桿旋轉限速；以及另一個水中舉升物體發生危險的議題。本文第三個探討的議題是四個支撐點喪失其一時，因為其相鄰的兩個支撐點之一為下一個可能失去反作用力之支撐點，因此構成兩條傾覆線，實際上臨界安定度的安定力矩等於傾覆力矩的那條傾覆線。由於移動式起重機結構複雜，模擬起重機吊掛之動作有各種變化的姿態，必須以電腦軟體輔助建模得到起重機各種姿態下的重量分布，以方便進行分析。本文以外伸撐座支撐，以吊桿相同側兩支撐座反作用力洽巧為零時之負荷作為傾覆條件，經由全域吊掛模擬計算傾覆荷重，得到吊掛作業之等荷重線，據以推斷出吊掛作業之在起重機四周的主要危險及次危險區域。

This study investigates the stability of lifting operation for a mobile crane. First of all, in accordance with international standards and national regulations to calculate stability grades basing on the tipping line composed by two supporting points of the crane. Proposed two extend topics, one of which is simultaneous occurrence of wind blow and crane rotate on a slope, estimation of rotating speed limitation for a boom should base on the linear superposition principle of combined load operating security equations. The other will be the danger of lifting submerged stuff. The third issue discussed in this article is the condition of losing anyone of four supporting points. In fact, this condition should be taken as the critical stability. Because the two adjacent supporting points beside the losing reaction point could create a tipping line, this means that the stability moment equal to overturning moment. Due to the complex structure of mobile cranes, there are various changes in postures at simulating of crane lifting operation. It must apply computer-aided modeling to obtain the distribution of weight under various postures of crane to facilitate analysis. This study uses extended legs to be supports, and applies the load of boom with the reaction force of opposite side supporting legs at zero as overturning condition. Utilizing the global lifting simulation to calculate the overturning load, the equal load line of crane lifting operation will be obtained and according to deduce primary and secondary dangerous zone.