Crane operation mechanism generally only uses four active and driven wheels, if the lifting weight is very large, the common way to increase the wheel pressure to reduce. When the wheels are more than four, the articulated balancing frame device must be used to distribute the load of the crane evenly among the wheels.
The metal structure of the bridge consists of main girder and end beam, and is divided into two types: single girder bridge and double beam bridge. The single girder bridge is composed of a single girder and an end girder located on both sides of the span. The double girder bridge is composed of two main girders and an end girder.