In 10 BC, Vitruvius, a Roman architect, described a type of equipment in his architectural manual. This machine had a mast with a pulley mounted on top; the position of the mast was fixed by cables, and the cable passing through the pulley was pulled by a winch to lift heavy objects. Some super-heavy machinery could use two masts to form an A-shape, allowing the lifted object to move horizontally, but the movement range was small and the operation was highly difficult.
This issue was not resolved until the rotating arm crane was invented in Italy in the 15th century. This crane featured an inclined jib with a pulley on top, which could lift, lower, and rotate. However, by the 18th century, all kinds of machinery used by humans still relied on human or animal power, which limited their lifting capacity, application range, and work efficiency. In the mid-to-late 18th century, James Watt improved and invented the steam engine, providing a power source for crane equipment. In 1805, Engineer Rennie from Glen built the first batch of steamships for the London Docks. In 1846, Armstrong from the United Kingdom transformed the steam engine at the New Fort Dock into a hydraulic machine. At the beginning of the 20th century, tower cranes began to be used in Europe.
A crane mainly consists of a hoisting mechanism, traveling mechanism, luffing mechanism, slewing mechanism, and metal structure: The hoisting mechanism is the basic working mechanism of a crane, mainly composed of a suspension system, a winch, and a hydraulic system for lifting heavy objects. The traveling mechanism is used to move heavy objects vertically and horizontally or adjust the working position of the crane, typically consisting of a motor, a reducer, a brake, and wheels. The luffing mechanism is only equipped on jib cranes; when the jib is raised, the luffing range decreases, and when the jib is lowered, the luffing range increases. It is divided into balanced luffing and unbalanced luffing. The slewing mechanism is composed of a driving device and a slewing support device for rotating the jib. The metal structure is the skeleton of the crane; main load-bearing components such as bridges, jibs, and gantry frames can be box-shaped structures, truss structures, or web member structures, and some can serve as support beams.