Issue 14

Bridges have for centuries been seen as symbols of man's civilising influence on the planet. A study of bridges throughout history reveals some key characteristics of the civilisations which created them. Think for example of the massive masonry blocks of the Pont du Gard in Roman France, or the pedestrian suspension bridges made from natural ropes in the high Himalaya. These reveal something about the nature of the society which built them.

Building is frequently compared, unfavourably, with other industries said to have modernised and improved much more dramatically over the period from the end of World War II. A typical such industry is motor vehicle manufacturing, and it is certainly hard to deny the incomparable improvements in motor vehicles today relative to those built only 1 or 2 decades ago. Similarly with aerospace, viewing aeroplanes from say, 50 years ago, looks increasingly like reading the pages from a history book.

Contrary to accepted belief, building conservation is not governed by rigid dogmas. It is prevented from being so because buildings are so varied in their history, quality, structural form and use. One rule cannot fit all; instead each building presents a particular set of problems, from the initial decision whether it should be retained or demolished to the question of what remedies should be applied; whether it should be conserved as found, or repaired, or in part replaced. Every case has both a philosophical and practical dimension.

The knowledge of construction methods, and the technology of the temporary works materials and products, that are integral to them, have been, and remain an essential part of the structural engineer's capability to deliver skills effectively. 100 years ago mechanisation was embracing the world of the motor vehicle, and the transport and material handling industry was in its early stages.

In the past 100 years engineers have contributed to mankind's management of disasters by keeping nature at bay with major infrastructure interventions, and by learning from previous events so as to be able to better design structures for appropriate levels of safety.

The construction industry in the UK underwent significant changes in the 20th century whilst reacting to and benefiting from the developing infrastructure and competition around the world. Throughout this time construction projects have used basically the same materials and workmanship skills although research and development has improved the understanding and performance of all concerned. Contractors now have sophisticated plant and equipment enabling faster excavations, the lifting of heavier loads and a reduction in the numbers of operatives with improvements in individual performances. The widespread use of calculators and computers in the last half of the century transformed conceptual appreciations, design and construction methods, communications and enabled easy access to sources of information.

This paper traces the development of the craft and science of foundation engineering in the UK during the last 100 years drawing mainly on papers published in The Structural Engineer. The story is told of how Terzaghi coupled engineering geology with the science of soil mechanics to provide the necessary rigour for modern geotechnical modelling and analysis. In the 1960s two innovative construction techniques combined to transform foundation engineering world-wide - large diameter bored piles and diaphragm walls. In recent years the use of numerical methods of geotechnical analysis has become widespread. The method opens the way for the instructive modelling of complex soil-structure interaction problems provided the inherent uncertainties are recognised. However, easy access to the computer packages poses grave dangers of inappropriate use of the methods. The risks and hazards posed by the ground are discussed and it is concluded that their effective management requires well planned and executed site investigations for all structures and the structural engineer has a key role to play.

The subjects of this review are treated in turn, in a manner inevitably selective. The past century can be summarised as two periods, separated by World War II, which both interrupted progress and changed its direction. Advances in knowledge are typically taken up by very few, and may be followed by several decades of development, often by trial and error. Only the few advances that show clear economic benefit receive wide application in practice. The growth in complexity of both methods of analysis and codes of practice is noted, as is the interplay in the route to qualification between tests set by the Institution and by others. The route is more accessible than in 1908, especially for women. The greater knowledge required is more readily available. Competition for professional training of high quality continues.

The world's seemingly insatiable search for power to support an industrialised economy has been a primary driver since the Industrial Revolution. Structures have been needed for the extraction of the energy source, for its conversion into useful power and for distribution. Structures have been needed to house the equipment for manufacturing and distribution of goods. Power needs industry and industry is greedy for power.

Despite the huge advancement in knowledge achieved over the last 100 years, we now live in a much more complicated engineering world than engineers inhabited at the inception of our Institution. For example, all the progress and perhaps bewildering variety of information outlined in this special issue of The Structural Engineer has to be assimilated and managed. As an industry we continue to live with major structural failures; the UK construction industry kills more people than any other industry; ill health arising from working in the industry is a major issue. We have projects that go disastrously wrong (in time, cost and client satisfaction); we spend more on litigation than we do on research. We have a constant need to educate the next generation to standards higher than their predecessors had to achieve. It is axiomatic that if our industry has progressed in knowledge over the last 100 years (or even one working generation of 40 years) there is much more for the current generation of engineers to learn and absorb.

Section 1. Structural engineering over the past 100 years.

Section 2. From the ground up: building high, enclosing space, spanning voids.

Section 3. Process and practice: tools of the profession.

Section 4. Facing the challenge of change.

We are living in ways that we know are unsustainable, but it is often hard to know how structural engineers should act to change this, especially if their role is narrowly defined. The increasing commitment to sustainable development by government, society and business is evident.

In 1908, The US cities of Chicago and New York had barely become used to seeing their new prestige buildings reach 25 storeys, and other cities would have to wait - some for several decades - to see even that level reached. In 2008, the Council for Tall Buildings and Urban Habitat's (CTBUH) list of the 100 tallest buildings throughout the world shows that they are all over 250m tall, typically 60 storeys. There are 35 'super-tall' buildings over 300m high already built and in use, with a further 55 under construction.

To understand the historical context of structural mechanics one needs to go back three centuries before the Institution of Structural Engineers was founded. In 1638 Galileo published an attempt to predict the strength of a cantilever beam. To illustrate his ideas1 he used the charming picture in Fig 1 of a cantilever beam set in to an overgrown and unstable looking wall. Unfortunately the integrity of his theory was of a similar standard to that of his wall. But this was the first lightening of the sky to herald the coming dawn of structural mechanics. The prediction of the strength of a beam became known as 'The Galilei Problem'. During the next 200 years the great applied mathematicians of Europe worked on the theory of bending and related topics. By the early 1800s many pieces of the structural mechanics jigsaw of ideas had been developed. There was a unique opportunity for someone to collect the prize for putting them together.

We sometimes lose track of the fact that structural engineering is something done by humans, for humans. I am a strong believer that we are people first, engineers second, and structural engineers third. And I believe that what unites us as people is much more than what divides us as engineers. So I’d like to look at the future of structural engineering through the people who might do it, and the changing world they will serve.

The story of structural engineering over the past century is one of men and women applying their knowledge and intellect to make possible the bridges, dams, tunnels, hospitals, concert halls, and every other type of built structure on which our lives depend. Structural engineers, working in collaboration with architects, builders, clients and a variety of professionals who form the teams behind complex projects, create the environment in which we want to live. They manage the risks of loading from wind, from gravity, from ground movement, from seismic shocks, and from people themselves, to make our structures safe to inhabit and enjoy.

This paper will attempt to offer insight into future challenges and changes for structural engineers in their ever-broadening field. While the past century and a half has witnessed manifold developments and achievements in all areas related to structural engineering, the presently increasing rate of material discovery and widespread optimisation will inevitably lead to unforeseen design possibilities. Inevitably, structural realisations will be attained which would be considered improbable today. This exploration will consider facets of praxis, building systems, materials science, and construction methods which will affect structural engineering and related fields, as well as their relationships to each other.

Although the Centenary which we are celebrating starts in 1908, the associated revolution in structural materials and techniques began in Britain around 1900, and earlier in America and on the Continent. Before 1900, bridges, land drainage, docks, harbours, cotton mills, train sheds and other essentially utilitarian works in Britain were civil engineering, while most other buildings were for people and were considered as architecture. Today this distinction is becoming less marked, largely due to the introduction of new materials and changes in attitudes to them.

The craft of building is of course ancient, but was originally just a skill lacking scientific backing. The development of engineering as applied science came much later and sprang from more general discoveries, from curiosity and from the practical needs of society. The desire to understand how our world works has motivated many, and polymaths like Leonardo da Vinci, were at least part engineers. In later times, groups gathered to learn and share their interests and in that sense, our Institution is the child of a long line of Learned Societies. In Britain, the Royal Society dates from 1660. Its first curator of experiments was Robert Hooke whom we might claim as one of our own. Newton was President from 1703 to 1727 and Thomas Young was a member (1773 to 1829), lecturing and writing prolifically with many of his works underpinning our current engineering understanding. These were the origins of where we are now and of the scientific method which is promulgated via Journal papers.

Along with tall buildings long-span structures appear as landmarks in the development of structural and constructional engineering. Record breaking bridge spans and the column free enclosure of vast spaces enable engineers to showcase the technological concepts that enable their construction and of course there is always an interest in record breaking.