Roman Engineering and Construction
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Roman Engineering and Construction Oxford Handbooks Online Roman Engineering and Construction Lynne Lancaster The Oxford Handbook of Engineering and Technology in the Classical World Edited by John Peter Oleson Print Publication Date: Dec 2009 Subject: Classical Studies, Greek and Roman Archaeology, Material Culture Studies Online Publication Date: Sep 2012 DOI: 10.1093/oxfordhb/9780199734856.013.0011 Abstract and Keywords This article concentrates on various aspects of Roman building technology. One of the most renowned of the Roman contributions to building technology was the development of concrete, which affected the vaulted roofing schemes, and bridge and harbor construction. The production of bricks in imperial Rome is a prime example of technological advance that resulted in increased organization rather than innovation. The development of large-scale vaulted structures is one of the most significant Roman contributions to the history of building technology and engineering. The structural reinforcement of vaults and arches, the technological advances in heating methods, and the vaulting techniques are all explored. Technological innovation in Rome occurs in response to a number of conditions including accumulated knowledge, evident need, economic possibility, and social/cultural acceptability, and a brief summary of the conditions that influenced Roman innovation provides some additional insight into the motivating forces within Roman culture. Keywords: Roman building technology, Roman engineering, Roman culture, concrete, bricks, vaults, arches, vaulting techniques, heating methods Page 1 of 28 PRINTED FROM OXFORD HANDBOOKS ONLINE (www.oxfordhandbooks.com). (c) Oxford University Press, 2015. All Rights Reserved. Under the terms of the licence agreement, an individual user may print out a PDF of a single chapter of a title in Oxford Handbooks Online for personal use (for details see Privacy Policy). Subscriber: University of Washington; date: 06 December 2017 Roman Engineering and Construction The Roman-Built Environment Strabo (5.3.8), writing in the Augustan period, notes that the Greeks were adept at founding beautiful and strategically located cities that took advantage of natural harbors and productive soils, whereas the Romans focused on practicality with the construction of roads, aqueducts, sewers, tunnels, and viaducts. With the benefit of hindsight we can also add man-made harbors to his list. Each of these is treated in other chapters of this volume. This chapter, however, presents developments that affected actual buildings, many of which occurred after Strabo wrote. The study of building technology involves two main issues: the available materials and the methods of putting them in place so that they stay put, which in modern parlance translates to “materials technology” and “structural engineering” (White 1984: 73). However, advances were also affected by the reorganization of work practices and the combination of existing technologies (Greene 1992: 101), a skill at which the Romans were most adept. The Romans drew on many technological innovations made in the Greek world, so with this in mind, I focus here on the aspects of Roman building technology that go beyond what had been accomplished earlier and thus provide insight into broader trends in the Roman world. Page 2 of 28 PRINTED FROM OXFORD HANDBOOKS ONLINE (www.oxfordhandbooks.com). (c) Oxford University Press, 2015. All Rights Reserved. Under the terms of the licence agreement, an individual user may print out a PDF of a single chapter of a title in Oxford Handbooks Online for personal use (for details see Privacy Policy). Subscriber: University of Washington; date: 06 December 2017 Roman Engineering and Construction (p. 257) Labor Supply and Contracts The acquisition of manpower for large projects, the legal framework in which it occurred, and the social institutions involved all played a role in the development of building technology. During the Republic, public projects were let out to private contractors (redemptores), usually by the censors or aediles using a contract called locatio conductio, which stipulated certain obligations for each party (Martin 1989: 29–40). A similar use of contractors for major public works continued during the imperial period, as attested by Frontinus (Aq. 2.119) and the funerary inscriptions of the redemptores who worked on such projects (Anderson 1997: 108–13). The use of multiple contractors within the same project may go some way in explaining the differences in building techniques found within a single project, such as at the Colosseum, Trajan's Markets, and the Baths of Caracalla (Rea et al. 2002: 370–74; Lancaster 1998: 305–8; DeLaine 1985: 196). Both architects and builders used measured drawings to communicate ideas, as indicated by Vitruvius (De arch. 1.2.2, 3.5.8) and demonstrated by examples preserved on papyrus, carved on walls and pavements, and depicted in mosaics and stone reliefs (Wilson Jones 2000: 49–58 with bibliography), but the differences in details within single projects suggest that there was a greater degree of flexibility in executing the instructions than one would expect today. Unfortunately, evidence for how large projects were overseen is scant. An inscription from Tunisia notes the use of an exactor to oversee four redemptores on a project in Thuburbo Maius (AE 1940.16), but for large imperial projects presumably an architect was involved. Social institutions, such as clientela, whereby persons of different social strata were bound by certain obligations for each other's welfare (especially in the case of freed slaves), also played a vital role in the way labor was acquired. DeLaine (2003: 723–32) has traced such connections between freedmen and former masters in the building industry at Ostia. This type of interaction was often financially beneficial for both parties and could provide incentives for technological innovations. The Arch, Vault, and Trabeated Architecture The Romans were known for their creative exploitation of the arch, and research has shown that it appeared in Rome by the sixth century B.C. (Cifani 1994: 194). The success of the arch relies on the radiating joints between the wedge-shaped voussoirs to direct the load toward the sides and away from the opening underneath. It is the optimal form for stone construction because the material is subjected to compressive rather than tensile stresses. Stone is very strong in compression but (p. 258) weak in tension, so a stone arch can span a larger distance than a flat stone beam, which undergoes both compressive and tensile stresses. Moreover, builders in Rome were relying on the local Page 3 of 28 PRINTED FROM OXFORD HANDBOOKS ONLINE (www.oxfordhandbooks.com). (c) Oxford University Press, 2015. All Rights Reserved. Under the terms of the licence agreement, an individual user may print out a PDF of a single chapter of a title in Oxford Handbooks Online for personal use (for details see Privacy Policy). Subscriber: University of Washington; date: 06 December 2017 Roman Engineering and Construction volcanic tuff, which has much less tensile strength than marble. The arch became a basic element for Roman architectural types such as the freestanding theater and amphitheater. It was translated into concrete construction, and the resulting curvilinear forms transformed the architectural vocabulary in the Mediterranean. Once travertine and marble became available in Rome in the late second and early first centuries B.C., the builders were also faced with lifting heavier stones of much larger dimensions than earlier. Lifting technology using cranes, ropes, pulleys and capstans came from the Greek world (Coulton 1974; see also chapter 13), but the Roman contribution was to use these elements on a scale far beyond what had occurred earlier (figures 2.4, 13.1). For example, the appearance of multiple lewis holes on single blocks, such as the 58-ton architrave of the Temple of Jupiter at Baalbek (first century A.D.), suggests that multiple lifting devices were coordinated and used together (Wiegand 1921: 66–67). From a much later period, the base of the obelisk of Theodosius at Constantinople (A.D. 390) depicts the use of multiple capstans to move the obelisk itself. No doubt similar techniques were used in the early second century in Rome to lift the blocks (25–77 tons) of Trajan's Column (Lancaster 1999). This procedure contrasts sharply with Pliny the Elder's (HN 35.96) description of the use of ramps to lift the massive architrave of the Temple of Artemis at Ephesus in the fourth century B.C. A significant difference between Greek and Roman stone architecture was in the construction of columns: the Greeks using stacked drums and the Romans preferring monolithic shafts. The Roman preference for monoliths had a great effect on the technological requirements of supplying the stone, and it also demonstrates the importance of reorganized work practices mentioned above. The period from the late first century B.C. to the early second century A.D. was one in which the imperial administration increasingly took control of quarries supplying marble for imperial projects (chapter 5). Wilson Jones 2000: 147–56) notes that this was also the period when a new type of standardized design procedure developed: what he calls the 6:5 rule, whereby column shafts were typically five-sixths the total height of the column (i.e., base + shaft + capital). This phenomenon appears from the Augustan period and is related to the production in imperial quarries of standard-sized roughed-out Corinthian capitals and of monolithic column shafts in lengths of multiples of either 4 Roman feet or 5 Roman feet (= RF). This rule of thumb resulted in a 50-RF column with a 40-RF shaft, a 48-RF column with a 40-RF shaft, a 36-RF column with a 30-RF shaft, and so on. Such standardization was only possible once the technology existed for the quarrying, transporting, and lifting of large monolithic shafts. An analysis of the Pantheon porch facade illustrates the types of issues that arose when building with the largest of these monolithic shafts.