Ordinary bridge cranes are generally composed of a lifting trolley, a bridge running mechanism, and a bridge metal structure. The hoisting trolley is composed of three parts: a hoisting mechanism, a trolley operating mechanism and a trolley frame.

The lifting mechanism includes a motor, a brake, a reducer, a drum and a pulley block. The motor drives the reel to rotate through the reducer, so that the steel wire rope is wound on the reel or lowered from the reel to lift heavy objects. The trolley frame is a frame that supports and installs components such as the lifting mechanism and the trolley running mechanism, and is usually a welded structure.

The driving mode of the crane operating mechanism can be divided into two categories: one is centralized drive, that is, a long drive shaft is used to drive the driving wheels on both sides of a motor; the other is driven separately, that is, one driving wheel on each side is used. Electric motor drive. Medium and small bridge cranes mostly use the "three-in-one" driving mode that combines brakes, reducers and motors. Ordinary bridge cranes with large lifting capacity often use universal couplings for easy installation and adjustment. .

The crane operating mechanism generally only uses four driving and driven wheels. If the lifting weight is large, the method of increasing the wheels is often used to reduce the wheel pressure. When there are more than four wheels, an articulated balanced frame device must be used to evenly distribute the load of the crane on each wheel.

The metal structure of the bridge is composed of main beams and end beams, which are divided into two types: single main beam bridge and double beam bridge. The single main beam bridge is composed of a single main beam and end beams located on both sides of the span, and the double beam bridge is composed of two main beams and end beams.

The main beam and the end beam are rigidly connected, and two ends of the end beam are equipped with wheels to support the bridge to run on the elevated frame. The main beam is welded with rails for the operation of the crane trolley. The structural types of the main beams of the bridge are more typical, including box structure, four-truss structure and open-web truss structure.

The box structure can be divided into several types: on-track box-shaped double beams, off-track box-shaped double beams, off-track box-shaped single main beams and so on. The box-shaped double beam on the right track is a basic form widely used. The main beam is composed of upper and lower flange plates and vertical webs on both sides. The trolley rails are arranged on the center line of the upper flange plate. Its structure is simple. It is convenient to manufacture and suitable for mass production, but its own weight is relatively large.

The cross section of the off-track box-shaped double beam and the off-track box-shaped single main beam are composed of upper and lower flange plates and main and auxiliary webs of unequal thickness. The trolley rails are arranged above the main webs, and the short stiffeners in the box body The slab can be omitted, in which the off-track box-shaped single main beam is replaced by a wide flange box main beam instead of two main beams. The dead weight is small, but the manufacturing is more complicated.

The four-truss structure is composed of four plane trusses combined into a closed space structure. The upper horizontal truss surface is generally covered with a platform plate, which has light weight and high rigidity. However, compared with other structures, it has large dimensions, more complex manufacturing, and fatigue. The intensity is low, and it has been less produced.

The open-web truss structure is similar to the off-track box-shaped main beam. It is composed of four steel plates to form a closed structure. Except for the main web which is a solid-web I-shaped beam, the other three steel plates are cut into many windows according to the design requirements to form a non-inclined bar. The upper and lower horizontal trusses are covered with platform plates, and the crane operating mechanism and electrical equipment are installed inside the bridge, with lighter weight and large overall rigidity. This is a type that is widely used in China.

Ordinary bridge cranes are mainly driven by electric power, which are generally operated in the driver's cab, but also remotely controlled. The lifting capacity can reach 500 tons and the span can reach 60 meters.

Simple beam bridge crane is also called beam crane. Its structure is similar to ordinary bridge crane, and its lifting weight, span and working speed are all small. The main beam of the bridge frame is a simple cross-section beam composed of I-beam or other section steel and plate steel. A hand chain hoist or electric hoist is equipped with a simple trolley as a lifting trolley. The trolley generally runs on the lower flange of the I-beam. The bridge frame can run along the track on the elevated frame, or along the track suspended below the elevated frame. This type of crane is called a suspended beam crane.