Trajan's Column - Construction

Construction

See also: Roman crane and List of Roman monoliths

It is assumed that the column drums were lifted by cranes into their place. Ancient sources, as well as a substantial corpus of archaeological evidence, prove that Roman engineers were capable of raising large weights clear off the ground. The typical drum of Trajan's Column weighs c. 32 t, while the capital, the heaviest block above the base and pedestal, is even at 53.3 t, which had to be lifted 34 m high. To save weight, the treads had probably been carved out before either at the quarry or in situ.

Even so, for such loads, the typical Roman treadwheel crane, which could only reach a maximum height of 15 to 18 m in any event, was clearly inadequate. Instead, a tower-like wooden construction was erected around the building site, in the midst of which the marble blocks were raised by a system of pulleys, ropes and capstans; these were powered by a large workforce of men and possibly also draught animals, spread out on the ground. According to modern calculations, eight capstans were needed to hoist the 55 t base block, while the length of rope required for the highest drums measured some 210 m assuming two-block pulleys.

Such a lifting tower was later also used to great effect by the Renaissance architect Domenico Fontana to relocate obelisks in Rome. From his report, it becomes obvious that the coordination of the lift between the various pulling teams required a considerable amount of concentration and discipline, since, if the force was not applied evenly, the excessive stress on the ropes would make them rupture. In case of Trajan's Column, the difficulties were exacerbated even further by the simultaneous work on the neighbouring Basilica Ulpia, which limited the available space so that the capstan crews had proper access only from one side.