WCCE-ECCE-TCCE Joint Conference 2 Seismic ProtecƟ on of Cultural Heritage October 31-November 1, 2011, Antalya, Turkey A HISTORICAL PERSPECTIVE ON EMPIRICAL AND RATIONAL DESIGN Thomas E. Boothby* INTRODUCTION c.1600, from L. empiricus “a physician guided by experience,” from Gk. empeirikos “experienced,” from empeiria “experience,” from empeiros “skilled,” from en “in” (see en- (2)) + peira “trial, experiment,” from PIE *per- “to try, risk.” Originally a school of ancient physicians who based their prac ce on experience rather than theory. Earlier as a noun (1540s) in reference to the sect, and earliest (1520s) in a sense “quack doctor” which was in frequent use 16c.-19c. (www.etymonline.com) In this paper, I will outline a viewpoint that incorporates two principal ideas: the fi rst is the central place that empirical design has held in the design of structures since an quity and through the present me. Perhaps this may not be diffi cult to believe for structural design up to the Enlightenment. However, I am convinced that empirical design holds a posi on of great importance in nineteenth century design and in contemporary design. In my inves ga ons of empirical design, I will follow Webster’s Dic onary of American English and defi ne empirical as ‘relying on experience or observa on alone o en without due regard for system and theory.’ On the other hand, I want to show that a concep on of scien fi c design has also been applied to the produc on of buildings since an quity. By scien fi c design, I mean the applica on of some ordered view of the ac on of nature, based on observa on and theorizing, to the produc on of buildings. In inves ga ng the terms ‘empirical design’ and ‘scien fi c design’ and what they mean to the engineering community, I hope to show that engineering in a modern sense: the applica on of an intellectual understanding of the universe to the produc on of worthy architecture-has been applied con nuously to the design of structures since ancient mes. On the other hand, I want to convince you not only that empiricism is a praiseworthy design method, but also that the 21st century engineering profession * Professor of Architectural Engineering, The Pennsylvania State University, USA, e-mail: [email protected] 1 A Historical PerspecƟ ve on Empirical and RaƟ onal Design unconsciously embraces empirical design, at least in part, because we couldn’t build anything without it. Thomas Kuhn (1962), in his discussion of the history of science and scien fi c inves ga on invites us to reconsider what we consider to be legi mate scien fi c inves ga on The more carefully they [informed historians of science] study, say, Aristotelian dynamics, phlogis c chemistry, or caloric thermodynamics, the more certain they feel that those once current views of nature were, as a whole, neither less scien fi c nor more the product of human idiosyncrasy than those current today. If these out-of-date beliefs are to be called myths, then myths can be produced by the same sorts of methods and held for the same sorts of reasons that now lead to scien fi c knowledge. If, on the other hand, they are to be called science, then science has included bodies of belief quite incompa ble with the ones we hold today. Kuhn argues in general that discarded scien fi c beliefs are no less true than the current understanding of phenomena in nature, but that they embraced a framework for explaining events which eventually became less tenable, and that was discarded for a new ‘paradigm’ or framework for the explana on of natural phenomena. In the same vein, I would ask us to reconsider some of the ways of analyzing and explaining structures. The descrip ons of medieval architects of the way that a structure works are not evidence of ignorance or supers on. Rather, the success that these men enjoyed in building monumental stone structures should speak for itself. An example might be found in an anonymous medieval architect’s descrip on of the construc on of support for the bells in a twel h century bell tower. ca. 1117 ‘Under the beams that hold up the bells, I placed an addi onal perpendicular beam at the top of the walls, fastened on both sides; and beneath this beam, suppor ng it, I placed a very strong wood column, and loca ng the base of the column on another beam, lying perpendicular to the lower beams from one side of the tower to the other. This was done in such a way that the weight of the bells and the wood suppor ng them, previously borne by 6 beams is now supported equally by 15 beams.’ (Mortet 1911) Perhaps we wouldn’t agree with this architect’s coun ng the collector beams and the columns and the joists equally, and there is certainly no ra onal analysis contained in this descrip on, but the principle stands: he has doubled the amount of support available to the bells. THE ANCIENT WORLD In the ancient world, there is a clear and sharp division between scien sts and mechanics, that is, people who think as opposed to people who do. This is presented, among others, by Aristotle, who dis nguishes mathema cs and physics, in brief, 2 Thomas E. Boothby scienƟ a, from ars facƟ va, such as building or medicine. The builder, prac cing ars aedifi caƟ va, the art of building, and the home that he is building are frequently recurring examples of Aristotle, and are an important manifesta on of the realiza on of poten al into ac on. He does express an interest in these arts, in the sense of regarding them as important, but concentrates his eff ort on the discovery of the ra onal make-up of the Universe. Mechanical Problems (He 1936), a short work a ributed to Aristotle, is much more prac cal than most of Aristotle’s work in its choice of problems, and o en in the ad hoc character of the explana ons that are advanced for the solu on of these problems. This is certainly one of the sources for an understanding of the Aristotelian dynamics described by Kuhn in the ini al quota on. The book is a series of ques ons rela ng to mechanics followed by explana ons. Some of the ques ons are par cularly relevant to the science of building. For example, Ques on 14, “Why is a piece of wood of equal size more easily broken across the knee, if one holds it at equal distance far away from the knee to break it, than if one holds it by the knee and quite close to it?”, or Ques on 16, which is taken up later in the seventeenth century by Bernardino Baldi. Both are answered in terms of the beam ac ng as a lever, with an external eff ort and internal resistance. Some of the earlier ques ons relate more directly to kinema cs, such as discussions of the composi on of mo on in two diff erent direc ons, or the kinema cs of circular mo on, which, according to Aristotle, consists of ‘natural mo on’ tangen al to the center and ‘forced mo on’ perpendicular to the center. Following Kuhn, we need to begin by reconsidering Aristotelian dynamics as a ra onal and construc ve world view. The features of this dynamics is the existence of natural and forced mo on: a substance has a natural mo on downwards (earth) or upwards (fi re) depending on its components. It can only be moved in a diff erent direc on by force or ‘violence.’ When the forcing is removed it reverts to natural mo on. Mo on can be combined, so that mo on can take place in a straight line (for equal parts natural and forced mo on), or in a curve (for varying parts). The principle of the lever holds in small and large machines. Figure 1 Composi on of Linear Mo on and Analysis of Circular Mo on 3 A Historical PerspecƟ ve on Empirical and RaƟ onal Design Much of what we know about theories of building in ancient Rome has been obtained from careful reading of Vitruvius. This book outlines rules of good building, and methods of good building for temples, private dwellings, public buildings, such as basilicae and theaters, and provides common-sense advice on construc on. The rules that Vitruvius presents are commonly cri cized as over-idealized, not used in actual construc on, as nearly as can be read from exis ng buildings, and an a empt to codify a process that is fl uid, empirical, and responsive to actual site condi ons. This cri cism can be answered by Vitruvius himself. In laying down his rules for the design of theaters, he says the following Nevertheless it is not in all theaters that the dimensions can answer to all the eff ects proposed. The architect must observe in what propor ons symmetry must be followed, and how it must be adjusted to the nature of the site of the magnitude of the work. For there are details which must be of the same dimensions both in a small, and in a large theater, for their use is the same. (V.vi.7) Certainly, according to Vitruvius, refi nements have to be made to general rules to accommodate the percep ons of the eye For the sight follows gracious contours; and unless we fl a er its pleasure, by propor onate altera ons of the modules, an uncouth and ungracious aspect will be presented to the spectators.