桥式起重机主梁的上拱是指以桥架两端梁的上平面为基准,主梁上平面相对于端梁上平面的向上弯曲。起重机主梁向上弯曲的最大值在主梁的跨度中心,此中心点的最大上拱值称为主梁的上拱度。主梁长度方向上各部位的拱度轨迹称为主梁的上拱度曲线,或简称拱度线。起重机主梁上拱度的大小和拱度曲线的形状对起重机的制造和使用是两项重要的技术 The arch of the main girder of the bridge crane refers to the upward bending of the plane of the main girder relative to the plane of the end girder with reference to the upper plane of the girders at both ends of the bridge. The maximum bending of the crane girder is in the center of span of the main girder. The maximum value of this central point is called the camber of the main girder. The length of the main beam of each part of the camber trajectory known as the main beam camber curve, or referred to as the camber line. The size of the camber and the shape of the camber curve of the crane girder are two important techniques for the manufacture and use of cranes