What are the application scenarios for the on-track box girders and off-track box girders of cranes?

The bridge crane’s main rail box girder structure is stable and easy to manufacture. The rail beam is subjected to uniform stress, with no torsion, and there is no need to calculate local compressive stresses. A drawback is whether the trolley wire rope will touch the edge of the main beam when the hook is at its lowest position. The walkway needs to be made larger. It’s not easy to arrange the cable holders, and it requires a lot of material. The deflected box girder can save some material, as a walkway may not be necessary, but it requires higher manufacturing standards; the web at the track-bearing section of the deflected girder must have local compressive stress taken into account, and the entire girder is subject to torsion. With numerous rib plates on the main beam, when the hook is at its lowest position, the trolley’s wire rope hardly touches the edge of the main beam, and the cable holders can be arranged more conveniently, saving material.

When deciding between a straight track and a curved track, it generally depends on whether the wire rope on the drum will interfere with the beam at the maximum lifting position. If there is no such interference, a straight track is usually chosen, as it offers better load-bearing capacity and a simpler structure; the downside is that the overall size of the crane becomes larger. Choosing an eccentric orbit generally does not cause interference, but the forces involved are more complex, and the overall structure becomes more compact. So it depends on the actual situation.