Abstract
Dear Michael, ladies and gentlemen, dear friends and colleagues,
I would like to welcome you all to the Karlsruhe Institute of Technology (KIT), formerly the University of Karlsruhe, for our Celebratory Colloquium in honour of Professor John Michael Rotter of the University of Edinburgh. As the KIT Department of Civil Engineering, Geo- and Environmental Sciences, we are very honoured to award Professor Rotter with the accolade of an Honorary Doctorate for his lifelong achievements in structural engineering.
This happy occasion falls exactly 10 years after a conference titled ‘Structures and Granular Solids, From Scientific Principles to Engineering Applications’ which was held at the Royal Society of Edinburgh in celebration of Professor Rotter’s 60th birthday. Already then its aim was to celebrate his ‘lifetime achievement in scientific research, particularly in the fields of structures, shells, silos and granular solids’. Now, and already 10 years on, we honour him and his life’s work with an Honorary Doctorate or, in German, Ehrendoktorwürde of the KIT.
Professor Rotter, or Michael as he is known to his friends, was born on the 31st of October 1948 in Chesterfield, in England, to a very erudite family with a strong tradition of engineering. He graduated from the University of Cambridge with a first class Bachelor of Arts degree in 1970, during which he developed a lifelong passion for structural mechanics, before moving to Sydney University to do a PhD on the behaviour of continuous steel–concrete composite columns subject to biaxial bending and elastic restraint under the guidance of Professor John Roderick, an extensive piece of work experimental, analytical, and computational in nature, finishing in 1977. He stayed on at Sydney as a Lecturer and Senior Lecturer, before moving to Edinburgh to take up the Chair Professorship in Civil Engineering there in 1988, and where he has been Professor Emeritus since 2015.
Michael has travelled the world widely, giving seminars and keynote lectures, and has acted as Visiting Professor in St Louis, Graz, Lyon, Nancy, Vienna, Hong Kong and is currently active at Imperial College London. He is a Fellow of most of the world’s most eminent learned societies in engineering, including the Royal Academy of Engineering, the Royal Society of Edinburgh, the American Society of Civil Engineers, the Institution of Civil Engineers, the Institution of Structural Engineers and the Institution of Engineers, Australia.
Michael has links to the university here at Karlsruhe going back several decades to the late 1980s during the time of the ‘Sonderforschungsbereich 219: Silobauwerke und ihre spezifischen Beanspruchungen’ (Specialist research area 219: Silos and their specific loadings) and the associated silo conferences in which our faculty was highly active. Michael participated in and presented at almost every one of the conferences of the Sonderforschungsbereich and formed lasting relationships at this time with many of our colleagues, including Professor Helmut Saal, Professor Peter Knödel, Professor Ulrich Schulz, Professor Dimitrios Kolymbas, Dr Cornelius Ruckenbrod, and myself, as well as Professor Josef Eibl from the Institut für Massivbau and Professor Gerd Gudehus from the Institut für Bodenmechanik und Felsmechanik. When he was travelling from Australia to Edinburgh to interview for his Professorship there, Michael made sure to stop over in Karlsruhe for a number of days. Later, we often met him in Karlsruhe for ECCS meetings on shell buckling. He has acted as the external examiner to PhD vivas at the Versuchsanstalt, and we later partnered with the University of Edinburgh for the European RFCS Combitube project. This project was a very productive and successful one, leading to several joint publications between Edinburgh, Imperial and Karlsruhe, and a major contribution to the European Standard on Metal Shells, Eurocode 3 Part 1-6.
Michael is thought of with much fondness and warmth by everyone here at Karlsruhe. We remember that he always took great and genuine interest in our work, and we remember the many very pleasant and inspiring discussions that were held together, often over beer and, sometimes, ‘gravel water’ (in German, ‘Kieswasser’). But we also remember how warm an interest he took in us as people, as individuals, in our hopes and aspirations, participating at our celebrations and dinners, to the point that, when he was visiting, it felt very much like someone from our close family was visiting.
This Honorary Doctorate is awarded to Michael Rotter in sincere recognition of all of his life’s work on the development of structural Standards as also for his many outstanding contributions in the wide research area he covers. In what is perhaps a privilege of our discipline, structural engineering worldwide is blessed with the Standard. It is a document that acts as a relatively state-of-the-art repository of the current body of knowledge. Its creation is not intended for the purposes of encyclopaedic archiving so that it may gather dust on a grand library shelf. Rather, once compiled, it forms an active part of the lives of practicing structural engineers, guiding them in their daily tasks of providing creative yet demonstrably safe and economical solutions to the complex designs that they must undertake on a daily basis. To some, the Standard is a handbook, a guidebook, but also a blunt tool with which to bring people to their senses. To others it is a bible, still spoken of with veneration even many decades after it was written, with some clauses held up as God-given laws of nature even when nobody remembers where they came from. Perhaps they came from some Professor, from somewhere, from sometime, from long ago …
Michael cut his teeth in Standards development in Australia. He co-authored the then state-of-the-art document ‘Design of Steel Bins for Bulk Solids’ Standard of the Australian Institute for Steel Construction in 1983; the ‘Guidelines for the Assessment of Loads on Bulk Solids Containers’ for the Institution of Engineers, Australia, in 1987; and finally, the ‘Loads on Bulk Solids Containers’ AS 3774 in 1990, the precursor to today’s Eurocode 1 Part 4 on ‘Actions in Silos and Tanks’. In what then symbolises a culmination of a lifelong endeavour to distill scientific advancement in structural engineering into a form that is directly accessible for and usable by society, Michael currently chairs three European Project Teams working on no fewer than five Eurocode Standards in the fields of metal shells, silos and granular solid pressures. These include, of course, the loading Standard for silos Eurocode 1 Part 4, the structural Standard on metal shells Eurocode 3 Part 1-6, and on plate assemblies Eurocode 3 Part 1-7, and the application Standards on silos and tanks, Eurocode 3 Parts 4-1 and 4-2 (to all the groups responsible for them, I am lucky to be a member). Together with other close colleagues, Michael had played an instrumental role in writing the first versions of these Eurocodes, working on them from the late 1990s up to their publication in the mid-2000s. This is not to mention the accompanying tome of Shell Buckling Recommendations, published under the auspices of the European Convention for Structural Steelwork ECCS, whose aim is to help the confused and bewildered to find their bearings in a jungle of limit states, capacity curves, buckling coefficients and partial factors.
Michael has long advocated a more holistic approach to structural engineering that exploits the computational tools that are now available to humanity, powerful tools that permit the limit state response of complex and complete structural systems to be determined with a high degree of precision. Designers, and design methods, need no longer limit themselves to hand calculation models which look at individual members in isolation, simplifications which were based on a high understanding of what could be ignored, but offered very little global predictive power. At the same time, Michael warned that while computational tools offered great predictive power, unless special case is taken this power may come with only limited understanding of what aspects of the mechanics are truly important. Putting every possible complexity into a structural model, for example, inevitably leads to an incomprehensible result, and probably also a wrong one. This is a major danger for designers and researchers alike.
It is then perhaps no surprise that, on Michael’s watch, the Shells Standard EN 1993-1-6 became (after the Draft of the DASt-Richtlinie 017 of 1992, which was based on work of Professor Herbert Schmidt, who is also here today and whom I cordially welcome) the first in the world to offer a formal framework for structural design assisted by finite element analysis, a reflection of the complexity that a designer is faced with in trying to dimension a metal shell structure. The Standard recognised that shells, appearing as they do in a myriad of geometries and with their resistance seriously affected by a complex mix of buckling, geometric imperfections, changes of geometry and plasticity, may be treated only perfunctorily by simple hand calculations. To this end, it introduced the ‘LA’, ‘LBA’, ‘GNA’ and all the way up to ‘GMNIA’ system of computational analysis acronyms that, together with a whole host of supporting ‘dos and don’ts’, has revolutionised not just the use of finite element analysis in structural design, but also in research, by permitting all of the possible nonlinearities that affect a structure to be separated out and uncoupled … put aside to be investigated one by one at one’s leisure, when one is ready … when one deserves it. In what is perhaps the ultimate endorsement, this classification scheme, devised for shells, has now grown legs and is beginning to become very widely used in other sub-disciplines of structural engineering, far beyond the field of shells. In the recent words of one Australian Professor, delivered during the Eurosteel 2017 Conference in Copenhagen, ‘many Standards could learn a thing or two from Eurocode 3 Part 1-6’.
Michael’s contribution to the silo construction and silo pressures also deserves a very special mention. It is a field that he entered perhaps by accident during his time in Australia under the gentle nudging of his former mentor Professor Nick Trahair, and it is this interest that originally led Michael to develop his relationship with Karlsruhe as part of the Sonderforschungsbereich. Silo structures is a field well known for its tendency to exhibit confounding behaviour, which at times leads to the total and catastrophic collapse of the silo, not least because its design lies far outside the comfort zone of a classical structural engineer who typically does not have a specialised education in either shell structures or granular solid behaviour. Michael has striven to bridge the gap between these two complex things, raising awareness of the dangers of making simplistic assumptions about the pressures that the granular solid may exert, and equally simplistic assumptions about how the shell might respond to them. He was often able to illustrate that, with only a bit of imagination and care, simple concepts from mechanics can actually be invoked to begin explaining very complex things, as long as they are the correct simple concepts.
One of his particularly important contributions was to the understanding and quantification of the phenomenon of eccentric discharge, where whether by design or by accident the granular solid discharges unsymmetrically from a silo structure. This leads to a loss of axisymmetry in the stress state within the shell and structurally damaging effects for both metal and concrete silos. This load condition is notoriously difficult to explore experimentally, as a very careful use of appropriate instrumentation must be made in order to estimate the pressures that occur during discharge and even to be to relate these to the pattern of discharge. Even with computational tools based on either continuum or discrete element treatments of the granular solid, the phenomenon remains elusive to reproduce reliably. Although much remains to be explored in this field, Michael has ensured that the European Standard Eurocode 1 Part 1-4 contains what is probably the first realistic pressure model for this condition, a model based on little more than a judicious and imaginative application of static equilibrium, and one that is already a valuable design and research tool, helping to explore and guard against this dangerous load case.
In 2001, Michael also wrote the so-called ‘red book’ or the ‘Guide for the Economic Design of Circular Metal Silos’. It is an authoritative reference for anyone seeking to understand how the theories of granular solids and shells may, and indeed must, be exploited in silo design. Michael, we hope very much that you may write a second edition one day.
The handful of European Standards and supporting publications represent the worldwide state of the art in the structural engineering practice of shells, silos and granular solids pressures, and the disciplines owe their current state in no small measure to the efforts, determination and dedication of Michael Rotter. This is, of course, not to mention the 450 or so scholarly contributions in numerous fields that Michael has authored and co-authored throughout his very productive career, including papers, books, book chapters, editorships, keynote speeches and expert opinions. The discipline of structural engineering is very lucky to benefit from such a talented person.
Among the many accolades due to Michael, I want now only to mention the Charles Massonnet Award which he received at the Eurosteel 2017 Conference in Copenhagen from the ECCS. It is awarded to prominent scientists who have contributed very significantly to the advance of scientific and technical knowledge for constructional steelwork. And now the circle closes: Charles Massonnet was also honoured by the Ehrendoktor of the Civil Engineering Faculty of the University of Karlsruhe in 1985. You can read his name among other very famous ones on the wall in the main entrance of our old civil engineering building (Altes Ingenieurgebäude).
I would like to extend a special thank you to you, Michael, for the many people who were lucky enough to be your colleagues, research partners and students over the years. Michael has not only been an inspiration to them and myself, the example of an out-of-the-ordinary structural engineer who impressed everybody. He has been a mentor and has had a profound influence on the directions in which research, projects and also lives have developed. Michael, it is an honour to know you and to work together with you.
Thank you very much.
