一、理论分析众所周知,对于图1所示的由钢索支承的起重机臂架AB,在变幅平面内,臂架的两端位置是固定的,但对于转动是自由的。因此,其有效计算长度l可取为等于其实际长度L,即l=L。在回转平面内,则情况稍微复杂一些。臂架的下端可以近似地认为在枢轴点A处位置是固定的,但回转受到弹性约束(如果支承处为塔式起重机的塔身,则塔身受力后产生扭转,所以可以看作为是弹性固定的)。臂架的头部 First, the theoretical analysis It is well known that for the crane jib AB supported by the cable shown in Fig. 1, both ends of the jib are fixed in the luffing plane, but are free for rotation. Therefore, its effective calculation length l can be taken to be equal to its actual length L, ie l=L. In the plane of rotation, the situation is slightly more complicated. The lower end of the boom can be considered approximately fixed at the pivot point A, but the swing is elastically constrained (if the support is the tower crane’s tower, the tower body is twisted after being stressed, so it can be seen as Elastically fixed). The head of the boom