Today, an architect or engineer assessing the structural safety of a historical construction needs to estimate the safety of the buttress system with accuracy
The buttressed core is a different species Permitting a dramatic increase in height, its design employs conventional materi- als and construction
THE ENGINEER IS TO PROVIDE THE FOLLOWING INFORMATION: i ) DIMENSIONS, SURFACE INCLINATION OR OUTLINE OF BUTTRESS ON ROCK FACE; ii) CONCRETE SURFACE FINISH
Many of these buildings, notably churches, include buttresses which were origi- The Rideau Canal was the largest civil engineering project undertaken at
Design Project Civil Engineering Design Project Your design and engineering team has been assigned the task of building a scale model buttress dam
construction can be considered to lie within the field of engineering today buttresses in France to provide the geometry for the structural studies
Proceedings of the Institution of Civil Engineers http://dx doi org/10 1680/stbu attention to the structural analysis of masonry buttresses Since
Department of Architectural Engineering and Construction Science how architectural design of flying buttresses affects the load path being transmitted
Jacques Heyman, Coulomb's memoir on statics: An essay in the history of civil engineering, Cambridge, 1972, reprinted 1997 Page 26 1216 Revue européenne de
The Creative Art of Structural and Civil Engineering casce princeton edu Physical Demonstration of Flying Buttresses in Gothic Cathedrals
Engineering education, unlike law, philosophy, art, or any field in the humanities, does not require
students to learn anything of the history of the profession. Engineering could be compared to medicine, which is a practical field with rapidly developing knowledge and with clear problems to solve. Similar to engineering education, medical students are not required to know the generalhistory of medicine, or even the specific history of a particular disease. Presumably the history of
the profession is irrelevant for the practitioners of the future. Fortunately, many engineers over the last century have researched the history of ancient and modern engineering and have made fundamental contributions to the field of construction history. This paper will not attempt to review the accomplishments of engineers in construction history, though the works of Jacques Heyman, Rowland Mainstone, and David Billington can be mentioned as examples of ground-breaking research. In fact, many of the problems facing the historian of construction can be considered to lie within the field of engineering today. The questions faced byhistorical builders are the problems that today's engineers attempt to solve. Some of these questions
are: How to build it? How much does it cost? How much material is required? Is it a safe design? What is the maximum possible span? What caused the failure of a large structure? All are questions that have been foremost in the minds of builders throughout history. Yet these questions are often neglected by historians of architecture, leaving room for engineers to analyse such historical problems in construction. Though these questions are primarily associated withstructural engineering, there are other aspects of engineering which can help to illuminate history,
such as material science, construction engineering, manufacturing, etc. This paper explores the role of engineering analysis in construction history and proposes opportunities and pitfalls for the future. In particular, the aim is to demonstrate how structural 89research projects will be used as examples to demonstrate the possibilities and to identify potential
perils for engineers working on historical topics. Each project is from a different time period and a
different region of the world, so they represent a variety of problems in construction history. The three topics are:Figure 2. Minimum thrust states of early flying buttresses in France, drawn at the same scale, with the darker
line showing the state of minimum thrust (after Nikolinakou et al. 2005) 91thrust, as illustrated by the sliding failure limit for a friction coefficient of 0.75. (fig.3) In fact, the
surviving flying buttresses appear to cluster on the safe side of the sliding limit. This suggests that
trial and error demonstrated this boundary of safe design. As Heyman (1995) has pointed out, measures were sometimes taken to prevent sliding at the head of the flyer, such as the addition ofcolumns under the head of the flyer. For example, the flying buttress at Saint-Julien in Royaucourt,
France, has experienced some sliding at the head of the flyer despite the use of a supporting column
affixed to the wall. (fig.4) Such movements may have occurred during the initial construction when the flying buttress acted at a state of minimum thrust.Figure 3. a) Minimum horizontal thrust values for flying buttresses with varying length-over-thickness ratios
and different inclinations; b) Corresponding thrust values for case study early Gothic flyersThere is tremendous potential for such studies to shed new light on the structure and construction of
historic masonry monuments. By developing new interactive limit analysis tools, researchers from awide variety of disciplines will be able to find new answers to old questions. The opportunities for a
new understanding of design and construction of masonry architecture can go together with new educational tools for students and professionals. By emphasising static equilibrium as the most important principle, a new level of understanding can emerge among historians of construction. Ongoing work at MIT aims to make such analysis methods more accessible for non-engineers (Block et al. 2006). Simple analysis tools are available for free over the internet for other researchers to use at http://web.mit.edu/masonry.This type of study suggests a number of perils for historians of construction as well. In some cases,
engineers are applying modern analysis tools that are not appropriate for historic structures. First
92semicircular arches of Figure 5, one with a thickness/radius ratio of 8% (fig.5a) and the other with a
ratio of 16% (fig.5b). A typical finite element analysis is shown on the left, in which the resulting elastic stress patterns in the masonry are indistinguishable between the two arches (Block et alstructures. The 8% arch will not stand unless the material can withstand considerable tension, which
is not the case for historic masonry construction. In short, elastic analysis says nothing about the
collapse state of masonry and cannot be used to describe the actual state of a historic masonry structure. Unfortunately, many e ngineers are applying elastic analysis to unreinforced masonry,which generally does not offer useful information for the historian. Elastic finite element analysis,
which purports to find the "one true state of a structure", is seeking exactness in vain (Ochsendorf
Figure 4. Sliding near the support of a flying buttress at Saint-Julien in Royaucourt,
fruitless, because without additional archaeological or historical knowledge, it would be difficult to
draw strong conclusions on the evolution of flying buttress designs. The desire to look for evolution
based on engineering analysis is tempting, but should only be undertaken with the appropriate 93engineering, there is a prevalent notion that each generation of engineers will surpass the previous
generation in a constant march of progress. With new technology (such as faster computers) engineering will always move forward to a more enlightened state of knowledge. Such notions are dangerous for modern engineering, and can be even more dangerous when applied to history.Figure 5. Two semicircular stone arches of varying thickness a) 8% and b) 16% are analysed by finite elements
(at left) and by thrust lines using limit analysis (at right). (Block et al. 2006)The example of flying buttresses has illustrated how the use of simple equilibrium analysis can shed
new light on the performance and construction of historic masonry structures. While this example has illustrated how engineering analysis can offer greater understanding of a specific element of a masonry building, the next example suggests that engineers can uncover wider societal questions that have been neglected by historians.The history of ancient suspension bridges is a fascinating topic which has scarcely been explored. In
ancient China, iron chain suspension bridges spanned long distances more than 1,000 years beforethe iron bridge at Coalbrookdale in 1779, which is often hailed as the first metal structure. Joseph
Needham, the historian of Chinese technology, has provided a starting point for the study of ancient
94the organization of the Inca state as well as the initial conquering of foreign lands. Garcilaso de la
Vega (1609) wrote a chapter titled "Many tribes are reduced voluntarily to submission by the fame of the bridge," saying: [The bridge] alone sufficed to cause many provinces of the region to submit to the Inca without any reservations, one being the part called Chumpivillca in the district of Cuntisuyu, which is twenty leagues long and more than ten broad. He was welcomed as their lord with a good will because of his face as a child of the Sun and because of the marvelous new work that seemed only possible for men come down from heaven.though they were crossing the bridge of Alcántara, or of Cordoba." But the Spanish reacted mostly
with fear. Pedro Sancho (1543) recalled how his first crossing terrified him: ...to someone unaccustomed to it, the crossing appears dangerous because the bridge sags with its long span... ...so that one is con tinually going down until the middle is reached and from there one climbs until the far bank; and when the bridge is being crossed it trembles very much; all of which goes to the head of someone unaccustomed to it. The sketch published by Squier (1877) gives a sense of the experience of crossing an Inca hanging bridge. (fig.7) The Inca suspension bridges successfully supported the loads of large armies in addition to the weight of horses and cannons, so it is apparent that these structures had significant load capacity (Ochsendorf 1996). As the Spanish became accustomed to the suspension bridges, they grew bolder, though they marvelled at the technology: I have seen many Spaniards cross without dismounting, and some on horseback at a gallop to show how little they were afraid: the feat is rather a rash one. The fabric is 96beyond the technical capacity of the Spanish at the time. Efforts to build a masonry arch bridge over
97load capacity of the bridges, the abutment details, the maintenance plans, the construction materials,
and the timeline and geography of bridge construction, engineers can make fundamental new contributions to our understanding of the development and organization of the Inca Empire. Ten years of the author's research has revealed that the bridges played a more important role in Andean history than anyone may have imagined before. By working together with historians and archaeologists, engineers can bring new context and new questions to the study of human achievement in construction. However, the study of ancient suspension bridges suggests an additional peril for engineers in the field of construction history. There is a danger of imposing modern ideas on historical constructions. A lack of historical knowledge or collaboration with experts in the field can lead engineers to impose modern notions on a historical society. Such is the case for the ancient Mayan city of Yaxchilan, where an engineer has proposed an enormous suspension bridge as a gateway to the ancient city (O'Kon 1995). The invented bridge has a level roadway, tall towers, and large anchorage blocks, which are all characteristics of modern suspension bridges. (fig.8) There is no historical, archaeological, ethnographic, or written evidence that the Maya ever built suspensionbridges. It is highly unlikely that a suspension bridge existed on this site, and it certainly did not
have the many modern features that are postulated. For example, the Maya did not have wheeled vehicles, so there would have been no need for a level roadway. The lesson from this example is that engineers should be cautious of their own lack of historical training and should work together with experts to ensure that the engineering studies are supported by historical and archaeological evidence. The example of Inca suspension bridges illustrates how engineers can raise new questions andillustrate new interpretations of the history of society. The final example suggests the potential for
engineers to contribute to the study of individuals in construction history. 98understand the technical and historical contributions of the company, it is necessary to examine the
originality of the work by each individual. Ongoing studies on this subject have shown that the son was responsible for the vast majority of the vaulting built in the United States and that his contributions have been overshadowed by his father's reputation as the founder of the company. Following his studies at the Escuela de Maestros de Obras (School of Master Builders) from 1861 to 1865, Rafael Guastavino Moreno began a successful career as an architect and builder in 99projects established him as a leading architect and builder of the period. His work was visionary in
terms of construction and design, though additional research is needed on the originality of Guastavino's work in Barcelona of the 1860's and 1870's. Without question, the dome of La Massa, spanning 17 metres with a rise of 3 metres and a thickness less than 10 centimetres, shows the ability of a great designer and builder (Dilmé and Fabré 2002). (fig.10) Figure 9. Promotional poster of the Guastavino Company (Source: Avery Library, Columbia University)The father and son each made substantial contributions to the development of the traditional timbrel
vault as an engineered structural system, extending the system well beyond anything built in Spainprior to 1900. As part of his efforts to create a modern constructive system, Guastavino Sr. carried
out controlled material testing at MIT in 1887. These results were used to develop design tables for
his arches, which Guastavino published in his first book (1892). As part of the construction process
for the Boston Public Library, Guastavino also carried out load testing of a timbrel vault in 1889, which he called "the first breaking load test ever made" (Mroszczyk 2004). Additional load testswere used in the future to promote the technical rigor of the construction method as well as to instil
public confidence in Guastavino's unknown system. The load testing was carried out mostly by the father prior to his death in 1908. 100Rafael Guastavino Jr. did not have formal training in architecture or engineering. He arrived in the
United States at the age of nine, and he began working in his father's office when he was only 11.His education came from years as an apprentice in the office, including training in graphic statics
from a senior engineer in the office. Remarkably, Guastavino Jr. received four U.S. patents in 1892 for innovations in tile vaulting when he was only 19 years old (Ochsendorf 2006). He also innovated by using metallic reinforcing as an integral part of the masonry construction system. Invault has the primary advantage that it can be built with no formwork, unlike the case of reinforced
concrete shells (Ochsendorf and Autuña 2003). Figure 12. Cathedral of St. John the Divine under construction, New York, 1909 (Avery Library, Columbia University) 102designed primarily according to equilibrium. His description of the thrust lines due to live loading
on a vault is a clear example of the "safe theorem" of limit analysis (Heyman 1995). (fig.13) Similarly, Rafael Guastavino Jr. designed using equilibrium methods of analysis and hiscontributions to the graphical analysis of domes are particularly interesting. The son was among the
first to adapt new innovations in the use of graphical methods for his design and construction projects. (fig.14) Such equilibrium methods of design for masonry are the correct approach, given the low values of stress in traditional masonry structures. Figure 13. Illustration of the live load carried on a tile vault with backfill (Guastavino 1892)study of such structural systems could be seen as a false trail in history, since the true path would
lead to the systems of reinforced concrete and steel that are prevalent today (Heyman 2005). Yet, it
is essential for engineers to research subjects such as Guastavino vaulting. By placing the accomplishments of such builders in their historical context, engineers can gain a new understanding of the development of structural innovations. Furthermore, the profession could discover potential possibilities for new design in the future. And the study of history could be a valuable resource in the crisis of civil engineering today, as described by Werner Lorenz (2003). There is great potential for improved engineering education by studying master works of the past and by emphasizing equilibrium methods of design. Finally, a greater appreciation for technical aspects of construction history could help to identify and preserve important works of construction history. 103systems. Thus, the peril for engineers is that historic buildings will be lost, perhaps causing the loss
of irreplaceable artefacts of engineering heritage. The loss of engineering history can be prevented
by engineers who take an active role in identifying and celebrating significant historical accomplishments.across the "two cultures." Anthropologists work together with biologists to understand the historical
104contribute to, ranging from the level of a single structural element, to the development of an entire
geographical region, and to the works of individuals. Yet, these three studies also suggest perils for
the profession of engineering. To summarise, engineers should: work closely with historians and archaeologists, and avoid a tendency to look for progress in structural history based on engineering analysis alone be careful not to impose modern approaches without considering the appropriateness of the approach work to identify and understand engineering heritage before it is lostThere are unlimited possibilities for engineering to contribute to the study of history and there is
ample room for the growth of research programs and university courses which focus on historical studies in engineering.Harth-Terre, E, 1961. "El historico puente sobre el río Apurímac," Revista del Archivo Nacional del