Of all the monsters that fill the nightmares of our folklore, none terrify more than werewolves, because they transform unexpectedly from the familiar into horrors. For these, one seeks bullets of silver that can magically lay them to rest. The familiar software project, at least as seen by the non-technical manager, has something of this character; it is usually innocent and straightforward, but is capable of becoming a monster of missed schedules, blown budgets, and flawed products. So we hear desperate cries for a silver bullet – something to make software costs drop as rapidly as computer hardware costs do. But, as we look to the horizon of a decade hence, we see no silver bullet. There is no single development, in either technology or in management technique, that by itself promises even one order-of-magnitude improvement in productivity, in reliability, in simplicity.
The original design assumptions regarding dynamic loading by pedestrians were checked. The guidance in the relevant UK bridge design codes had been followed, with additional input from overseas codes and non-statutory documents. The codes advise on the level of force to be assumed in design, and the amount of movement which is acceptable to users of a bridge. The UK bridge codes require only vertical excitation to be considered. In the original design all critical vertical modes of vibration were examined. The size of the applied loading recommended in the bridge design code was increased by 33 per cent to give the design additional robustness. The original design also considered loading due to groups of vandals deliberately attempting to excite the bridge. Extensive additional research was carried out during the original design, including database searches on suspension bridges. (Arup, 2000a)
The bridge was open for three days, between Saturday 10 June and Monday 12 June. At times it was very crowded, with some 2000 people along its length. An estimated 80,000–100,000 people crossed on the opening Saturday. When the bridge was crowded, the south and centre spans suffered lateral vibrations large enough to cause pedestrians to stop walking or to hold onto the balustrades to regain their balance. The movement of the south span, between Bankside and the first river pier, was a combination of horizontal and torsional (twisting) oscillations. Observations on the day and studies of video footage show up to 50 mm movement, depending on the number of people walking. The frequency of the movement was about 0.77 cycles/second. The centre span moved by up to 70 mm at a frequency of 0.95 cycles/second, mainly horizontally. This part of the bridge was observed to oscillate when occupied by more than about 200 people. The north span did not move substantially. It was decided to control the number of people present on the bridge from noon on the Saturday onwards. The concern was the safety of individuals, rather than any risk of structural failure of the bridge itself. The bridge was closed on 12 June pending investigation into the cause of the unexpected movements. (Arup, 2000a)
The results of this review and comparison show that, apart from the unexpected movement, the bridge is reacting as predicted. There are some marginal – and explicable – differences in the figures but none represents a significant departure from the model, and none could explain the unexpected movement. (Arup, 2000b)
A programme of research was undertaken during the summer of 2000. A solution was then developed using the results of these tests. Arup has warned other bridge designers of their findings and the British Standard code of bridge loading is being updated to cover the phenomenon, now becoming referred to as Synchronous Lateral Excitation. The research indicated that the movement was caused by the sideways loads we generate when walking. Chance correlation of our footsteps when we walk in a crowd generated slight sideways movements of the bridge. It then became more comfortable for people to walk in synchronisation with the bridge movement. This instinctive behavior ensures that the sideways forces we exert match the resonant frequency of the bridge, and are timed such as to increase the motion of the bridge. As the magnitude of the motion increases, the total sideways force increases and we becomes more correlated. The sway movement is not specific to the Millennium Bridge. The same excessive sway movement could occur on other bridges, future or existing, with a lateral frequency under ~1.3 Hz and with a sufficient number of pedestrians. During the investigations Arup discovered that other bridges with completely different structures to the Millennium Bridge have swayed sideways when crowded, for example the Auckland Harbour Road Bridge during a demonstration in 1975 […]. These cases have not been widely published and as a result the phenomenon has not become known to practicing bridge engineers. (Arup, 2005)
Protection of the elegance of the bridge has been a key aim. The design solution has evolved in weekly meetings with Foster and Partners and discussed in detail with Sir Anthony Caro and Lord Foster. […] The additional structure and dampers under the bridge deck do not affect the side elevation since they are located above the level of the transverse arms and therefore behind the deck edge tubes. The structure which will be visible on the bridge elevation will be: The diagonal viscous dampers at the piers. These are located in the plane between the cables and the edge tubes and extend two bays along on each side of the pier. The two viscous dampers on each side of the south abutment ramp. These are arranged as an inverted ‘V’ and are located on each corner of the ramp junction where it splits in two and turns parallel to the river bank. The underside of the bridge is an important feature of the design. One of the main views of the bridge is from each bank and from river boats, where the soffit is plainly visible. The chevron shaped bracings have been designed with this in mind and are aligned with the bridge centreline and spaced at regular intervals. Similarly, the tuned mass dampers are arranged regularly and placed between the underside of the deck and the top of the transverse arms.
If we know exactly the laws of nature and the situation of the universe at the initial moment, we would predict exactly the situation of that same universe at a succeeding moment. (Poincaré, 1995 [1903])
More than any other single group, the Lunar Society of Birmingham represented the forces of changes in late eighteenth century England, for the Lunar Society was a brilliant microcosm of that scattered community of provincial manufacturers and professional men who found England a rural society with an agricultural economy and left it urban and industrial. […] Together they comprised a clearing-house for the ideas which transformed their country materially, socially, and culturally within a generation. They were men of broad interests and their discussions ranged widely, but their major mutual interest was the sciences, pure and applied – particularly as applied to the problems of industry.
[…] the growing body of facts, experience and skills in science, engineering and technology disciplines; coupled to an understanding of the fields of application. […] It is mainly ‘experience-based’ knowledge, which is more difficult to describe and communicate than ‘codified knowledge’ because it must be put into the context of an application. Engineering knowledge ranges from the more traditional such as civil, mechanical, electrical, chemical, automotive, aeronautical, to the newer such as electronic, communications, medical, bio-technical. These subjects are being added to regularly. (Royal Academy of Engineering, 2000)
based on the generic procedures carried out by an engineer in solving an engineering problem and delivering the solution. Engineering problem solving is an iterative task involving creativity and the application of knowledge and understanding. Broadly, an engineer needs to be able to identify and describe the problem that is to be solved … The solution will have a specification with parameters that require evaluation, a process that relies on the engineering skills of conceptualisation, determinable modelling and analytical representation. Delivery of the specified solution draws on other skills including the verification of conceptual models by experimentation with physical models.
Engineering process | Scientific process |
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Invention, design, production | Discovery (mainly by controlled experimentation) |
Analysis and synthesis of designs | Analysis, generalisation and synthesis of hypothesis |
Holism, involving the integration of many competing demands, theories, data and ideas | Reductionism, involving the isolation and definition of distinct concepts |
Activities always value-laden | Making more-or-less value-free statements |
The search for, and theorizing about, processes (e.g. control, information, networking) | The search for, and theorizing about, causes (e.g. gravity, electromagnetism) |
Pursuit of sufficient accuracy in modelling to achieve success | Pursuit of accuracy in modelling |
Reaching good decisions based on incomplete data and approximate models | Drawing correct conclusions based on good theories and accurate data |
Design, construction, test, planning, quality assurance, problem-solving, decision-making, interpersonal, communication skills | Experimental and logical skills |
Trying to ensure, by subsequent action, that even poor decisions turn out to be successful | Using predictions that turn out to be incorrect to falsify or improve the theories on which they were based |
The first was never to accept anything as true if I had not evident knowledge of its being so; that is, carefully to avoid precipitancy and prejudice, and to embrace in my judgement only what presented itself to my mind so clearly and distinctly that I had no occasion to doubt it. The second, to divide each problem I examined into as many parts as was feasible, and as was requisite for its better solution. The third, to direct my thoughts in an orderly way; beginning with the simplest objects, those most apt to be known, and ascending little by little, in steps as it were, to the knowledge of the most complex; and establishing an order in thought even when the objects had no natural priority one to another. And the last, to make throughout such complete enumerations and such general surveys that I might be sure of leaving nothing out. (Anscombe and Geach, 1970, pp. 20–21)
… the conjunction of these simple natures with one another is either necessary or contingent. It is necessary when one is implicitly contained in the concept of the other, so that we cannot distinctly conceive of either if we judge that they are separated […] A combination of natures is contingent when they are not conjoined by any inseparable relation; as when we say that a body is animated, a man is clothed, etc. (Anscombe and Geach, 1970, p. 174)
Automatic insertion | 15 | |
Manual assembly | 125 | |
Dual wave soldering | 60 | |
Average monitoring internal | 600 | |
Testing | 300 | |
Time taken to correct settings | 600 | |
Mean control lag | 1700 | ≈28 minutes |
The Society for General Systems Research was organized in 1954 to further the development of theoretical systems which are applicable to more than one of the traditional departments of knowledge. Major functions are to: (1) investigate the isomorphy of concepts, laws and models in various fields, and to help in useful transfers from one field to another; (2) encourage the development of adequate theoretical models in the fields which lack them; (3) minimize the duplication of theoretical effort in different fields; (4) promote the unity of science through improving communication among specialists. (von Bertalanffy 1968, p. 13)
From its inception in the days following World War II, RAND has focused on the nation's most pressing policy problems. High-quality objective research on national security became the institution's first hallmark. In the 1960s, and in the same spirit, RAND began addressing major problems of domestic policy as well. Today, RAND researchers operate on a uniquely broad front, assisting public policy makers at all levels, private sector leaders in many industries, and the public at large in efforts to strengthen the nation's economy, maintain its security, and improve its quality of life. They do so by analyzing choices and developments in many areas, including national defense, education and training, health care, criminal and civil justice, labor and population, science and technology, community development, international relations, and regional studies. (RAND, 2000)
… an inquiry to aid a decision-maker choose a course of action by systematically investigating his proper objectives, comparing quantitatively where possible the costs, effectiveness, and risks associated with the alternative policies or strategies for achieving them, and formulating additional alternatives if those examined are found wanting. (Quade, 1967)
In our earliest study of production systems [in coal mining] it became apparent that ‘so close is the relationship between the various aspects that the social and psychological can be understood only in terms of the detailed engineering facts and of the way the technological system as a whole behaves in the environment of the underground situation’. An analysis of a technological system in these terms can produce a systematic picture of the tasks and task inter-relations required by the technological system. (Emery and Trist, 1960)
‘… the basic unit for the design of socio-technical systems must itself be a socio-technical unit and have the characteristics of an open system.’ the second aspect of systems design was the recognition that the arrangement of parts, and the principles on which that arrangement were based, were important principles the third principle was that ‘… higher levels of organization can be achieved only by the fuller use of the inherent properties of parts as co-determinants of positional values. […] what this principle means is, quite simply, that the best design for any productive system will be that which not only allows that the goals of any subsystem, any part, embody in some manner the overall system goals … and allows that any such part is self-managing to the point that they [sic] will seek to cope with external variances by firstly rearranging their own resources …’ (Emery, 1981, pp. 387–88)
ICI was realising at that time that the operation of a petrochemical complex, in which the output from some plants is the input to others, entails engineering the whole as a single complex system. This was different from building and operating a plant to make a single product, and it seemed to some forward-looking managers in ICI's then Agricultural and Heavy Organic Chemicals Divisions that it would be useful if this kind of problem were being addressed by some university-based group: hence the gift to Lancaster. (Checkland and Scholes, 1990, p. 16)
In a sudden mood of anger, I made the remark, ‘The whole problem comes from the fact that there is so much tinkering with software. It is not made in a clean fabrication process’, and when I found that this remark was shocking to some of my scientific colleagues, I elaborated the idea with the provocative saying, ‘what we need is software engineering.’ (Bauer, 1993)
A system is an integrated combination of components designed to follow a common purpose. A systems philosophy demands that an unco-ordinated, piecemeal activity is replaced by a co-ordinated approach in which the identity of the separate parts of the system are subsumed by the identity of the total system. Systems engineering is an art, based on control systems principles, for designing complex systems. Individual elements and subsystems are fitted together to achieve an overall system purpose objective in the most effective way, at the lowest cost, with minimum complexity.
Systems engineering is a set of principles, methods and techniques applied to all the tasks involved in all the life cycle stages of a complex system.