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Department of Engineering

Honorary Degree for Professor Jacques Heyman

Honorary Degree for Professor Jacques Heyman

Professor Jacques Heyman

Professor Jacques Heyman, formerly Head of the Department and a leading figure in church architecture and restoration was awarded a degree Honoris Causa by the Universidad Politécnica de Madrid on 28th January 2008.

It is a great honour, for the Polytechnic University of Madrid, that Professor Heyman joins our Doctors Honoris Causa.

Professor Aroca

The degree was proposed by the Spanish University’s School of Architecture in recognition of Professor Heyman’s work in the engineering analysis of masonry structures.

Professor Heyman read engineering at Cambridge and in 1946 joined a Cambridge-based research team working on the plastic (i.e. inelastic) design of steel buildings. The work led to a PhD, and he then spent a post-doctoral year at Brown University. He returned to Cambridge as a University lecturer and Fellow of Peterhouse.

Professor Heyman made a name for himself by applying the plastic principles of steel structures to the analysis of masonry buildings. This introduction of modern techniques into older masonry buildings made him the world's leading expert in cathedral and church engineering. In 1971 Professor Heyman was responsible for the restoration of Ely Cathedral’s Great West Tower.

After his retirement Professor Heyman became a consultant and is still concerned with cathedral and church restoration projects. He gave courses of lectures at Florence University and has also served as a member of the Architectural Advisory Panel for Westminster Abbey, as well as the Cathedrals Fabric Commission for England. The Archbishop of Canterbury recognized his work by the award of the Cross of St. Augustine in 2005.

The oration by Professor Aroca at the award ceremony in the Spanish capital spoke of his major contribution in recognising the applicability of plasticity theory to masonry structures:

"Professor Heyman is the author of a large number of important books and articles, he has worked and works as a consultant on masonry structures, he was until his retirement, Head of the Engineering Department of Cambridge University, where he succeeded Professor Sir John Fleetwood Baker in the post, although the formal succession was delayed for a few years, and at the age of 82 he enjoys an extraordinary physical and mental health; it is hard to believe that he was already actively collaborating on a fundamental advance in the theory of structures, when the majority of you here today weren’t born and some of us, who are no longer young, were only children.

"His technical and scientific contributions are full of clarity and common sense with the intention of finding and explaining the essential questions/issues and putting them forward in the simplest possible manner. Like him, some of us still believe that complex set ups based on calculation subtleties are capable only of offering an unreal accuracy, given that it is not possible to work from hypothesis with suitable reliability, and therefore cannot be useful unless the behaviour of the structure is also understood."

Full oration by Professor Aroca (Translation by Alejandra Albuerne)

"It is a great honour for me to address you on behalf of the Polytechnic University of Madrid in this ceremony to honour Professor Jacques Heyman by conferring a Doctor Honoris Causa Degree on him, following the proposal of the School of Architecture.

"To understand the crucial role Professor Heyman has played in understanding the structural behaviour of buildings we should go back in time.

"Until the 19th Century Construction was an empiric art based on geometrical rules; its structural side started to appear in the scientific field in 1638 with the publishing by Galileo of his “Dialogue about two new sciences” (Galileo had some problems with the Church, who had serious, and mistaken, opinions about the mechanics of celestial bodies, but fortunately didn’t have an opinion on the mechanics of solid bodies).

"In the western tradition, there is an underlying certainty, as a Greco-Judaic legacy, that the world is ruled by simple laws that are waiting to be discovered (now we would say all the laws are only mental constructions that enable us to approximate or describe natural phenomena). The work started by Galileo, which discredits the rules of proportion and establishes the basis for the modern understanding of structures, is continued by other philosophers (in the 17th century, the scission of the natural philosophers, later scientists, hadn’t taken place yet, giving up metaphysics to future self-named “philosophers”).

"The 18th century and most of the 19th century witnessed the development and nearly the end of the science of structures; towards the end of the 19th century, the laws and concepts of the elastic theory of structures are expressed extremely clearly, only some technical aspects were still pending on the mathematical resolution of differential equation systems, equations that were not solved until the second half of last century. Some of us present here today had the privilege of witnessing the spectacular development of numerical analysis, having far exceeded the point from which the designer was able to ignore annoying calculations, it has reached the extreme of making them believe that it is not even necessary to dominate the concepts, but despite its impact, this has been only a technical development on the scientific base established in the 19th century.

"Without wishing to show any disrespect for the fantastic technical progress in analysis: In my opinion, there has been only one essential contribution to the science of structures in the 20th century.

"From the later years of the 19th century, steel structures were being built but nobody thought it necessary to verify if their behaviour corresponded to the theoretical predictions.

"Between 1931 and 1936, as part of the work editing a design code for the elastic analysis of steel frames and under the auspices of Baker, a series of measurements of real structures were made. The results of these showed a serious disagreement between the perfect theoretic model, which was the basis of the science of structures, and reality. This was directly related to the initial state and the boundary conditions.
The easiest way to illustrate the problem is:

  • When someone sits on a three legged stool, it is possible to calculate the ground reaction on each of the legs.
  • For a four legged stool, it is impossible; the geometrical perfection of the stool, the ground topography and even the cleanness of the stool (data impossible to introduce in the model) have a decisive effect on the result.

"Real structures are stools with many legs, imperfectly constructed and resting on a ground that defies any precise/exact definition.

"In 1936 it was evident for Baker that a new approach in the analysis of structures was necessary. Predictions in a closer agreement with the actual results, which were considerably less random than the elastic measurements, could be obtained if the possible deformations/strains in the plastic range of steel were considered. The Second World War interrupted the work, however by 1948 Baker had a calculation method but it still lacked a solid conceptual base. The contribution of Prager at the time with the American University of Brown, was decisive to the progress of developing it. The theorems of the “ultimate load” are the latest theoretical contribution to the science of structures.

"The collapse load of a structure has a specific value, equal to or larger than that obtained from equilibrium equations, and equal to or smaller than the value obtained from a possible mode/mechanism of plastic displacements/movements.

"Limit analysis, whose practical application preceded the rigorous enunciation of the theorems, allows us to obviate the issues of the the initial state and the boundary conditions.  Heyman was there at the time this crucial contribution was formulated. He arrived in Cambridge in 1941, at the age of 16, with the intention of studying mathematics, but the following year he changed to engineering and graduated in 1944, when the world was still at war and was demobilised in 1946. He returned to Cambridge and joined Baker’s team as a research assistant, he gained his doctorate in 1949 and moved to Brown University to work with Prager for one year plus another year in 1956. Except for a very short period of time spent at Oxford, he developed his academic career, which reached its peak as head of the Engineering Department, back at Cambridge.

"While working in Baker’s team he collaborated in the development of the mathematical basis of plastic theory. It is not in his nature to claim merits, but he cannot conceal that he was able to understand and publish in 1966, in his fundamental work “The Stone Skeleton”, that an approach to the analysis developed for steel structures was perfectly applicable to masonry structures. Hence he had proved the general applicability of the theory, beyond the material, endowed traditional systems of verification with a solid theoretical base and established a rational process of analysis that he has applied to several extraordinarily important buildings.

"Quoting him, not literally: In 1638 Galileo breaks away from geometrical rules and opens the way allowing us to check structures based on strength and stiffness; fabric structures are much more rigid/stiff than strictly necessary, so it is not necessary to check either of those aspects; the analysis should be based on equilibrium, which finally leads to a correct understanding of its geometry in order to verify its safety through the consideration of  limit states.

"At this point, I can’t avoid telling a story that happened some 25 years ago: Saez de Oiza was in charge of maintaining and restoring the Cathedral of Leon and he came up to me amazed: “I have had a finite element analysis of the cathedral done and the cathedral stands because the top, straight, layer of the flying buttresses is made of granite, which has a higher elastic modulus than sandstone.” I tried without success to convince him that, without even taking into account other problems, at that moment in time it was not yet possible to solve equation systems, other than plane ones. Therefore, for a gothic structure, not even a reasonable geometric modelling could be done.

"Some days later, very worried, he told me, “after all, it is not granite but sandstone painted grey”. I replied: “then it will collapse and at last you will have the certainty of going down in history as the person responsible for the collapse of the Cathedral of Leon”. To my surprise the following day, while the cathedral was still standing, he resigned from the job.

"Professor Heyman is the author of a large number of important books and articles, he has worked and works as a consultant on masonry  structures, he was until his retirement, Head of the Engineering Department of Cambridge University, where he succeeded Baker in the post, although the formal succession was delayed for a few years, and at the age of 82 he enjoys an extraordinary physical and mental health; it is hard to believe that he was already actively collaborating on a fundamental advance in the theory of structures, when the majority of you here today weren’t born and some of us, who are no longer young,  were only children.

"His technical and scientific contributions are full of clarity and common sense with the intention of finding and explaining the essential questions/issues and putting them forward in the simplest possible manner. Like him, some of us still believe that complex set ups based on calculation subtleties are capable only of offering an unreal accuracy, given that it is not possible to work from hypothesis with suitable reliability, and therefore cannot be useful unless the behaviour of the structure is also understood.

"It is a great honour, for the Polytechnic University of Madrid, that Professor Heyman joins our Doctors Honoris Causa."

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