Pages which introduce each topic

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Types of bridges and how they work

Building bridges

Parts for bridges

Materials for bridges

Basic rules

Forces and what they do

Stresses and strains

Measuring forces

Bending moments

Joining spans

Model bridges

F A Q about bridges


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You may find that this web-site is not as tidy as you might wish. This is partly because the real world is not as tidy as you might wish, either.

This web-site is as much concerned with the relationships between apparently different phenomena, and the fuzzy boundaries between different ideas, as in making sharp and clear distinctions, which may not map exactly on to reality. Of course we need categories like arch, beam, and so on, but we also need to ask whether they are in all cases totally distinct.  

This web-site is also not at all concerned with the biggest and longest structures, most of which most of us will never see. What it does try to do is to suggest that if we look around at ordinary things and ask how they work, we are much more likely to understand the big and famous things a bit better when we see them.  

Some amazing discoveries have been made by people who could see beyond the boundaries of individual intellectual and practical disciplines, and many valuable technologies have resulted from this type of work. This has been a very prominent development in recent decades, though it is of course not new. The first device for making visible the paths of elementary particles and other ionizing particles was devised by a man who had been studying fog. This was C T R Wilson's cloud chamber. The idea for the more recently invented bubble chamber surfaced when Donald Glaser was idly watching the bubbles rising in his beer. But his mind wasn't idle: in fact, it is often when then the conscious mind is idle that the ideas come bubbling up from the unconscious mind.

It is quite possible that if you have come here to find information for a compulsory project about bridges or some other structure, you may be bored and uninterested in the whole subject - well - just do what you have to do. Most people can do well in something they care about: to do do well when you are not interested is an achievement in itself.

If you want to send a suggestion or a criticism of any part of this web-site, please do; several changes have already been made as a result of people writing in. It is too late to make big changes to the structure of the site, but all the pages linked from this page were written as a result of one person's comments about the complexity of the site and its contents.

A real problem with any attempt to help people to understand something is that different people look at things in different ways. It is also true for many people that an explanation that they have found by their own thinking will stay with them far longer than what they were told by someone else. This web-site includes pages of links to enable you to look for different ways of understanding things.

In any case, whatever you want to do or understand, don't be put off by "experts" who seem to make it very difficult. They may be simply trying to maintain their status, or they may genuinely not understand things very well themselves.

There is usually a sense in which everything is simpler than it seems, if only the right description is found. On the other hand, an explanation that is wrong, however easy or attractive it seems, is useless. An example is the explanation of lift generation by a wing in terms of the air above the wing "having further to go." This is wrong on two counts, firstly, it doesn't explain how a flat plate can generate lift, and secondly, and much more seriously, "further to go" has no meaning because the bodies of air that pass over and under the wing do not come together "in step" after passing the wing. If you find any errors or omissions in this web-site, please let me know. I do not wish to propagate errors.

There is also a sense in which everything is more complicated than it seems, especially when you actually try to make something that actually works, as opposed to simply producing a web-site like this. Many of the basic equations of science and engineering are simple to write down, for example, Maxell's equations, Schrödinger's equation, Dirac's equation, Einstein's general relativity equations, Navier-Stokes equation. Many are the people who will tell you that they are beautiful, but few are those who can solve them. But you don't always have to solve the equations, or even to know what they are, in order to build something that works. Nevertheless, being able to solve equations might just gain you that small extra factor of efficiency that makes the difference between profit and loss, or even possible and impossible.

Few of us can aspire to the intellectual level of the lecturer who stands before the students and dazzles them with his brilliance: the rest of us can only stand beside the student and try to shine a little light on the subject.

Engineers in Britain



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