I receive a lot of letters, via both snail mail and email, from readers of my books and articles, and much of the correspondence comes with enclosures or attachments containing images of artistic, beautiful, clever, dramatic, elegant, fantastic, and sometimes just downright zany designs. What they all seem to have in common is that the sender of the image wants to share the joy of having come across some device, structure, or system that brings a smile to the face. There is just something about a good design that makes you feel proud to be part of the ever-creative and astounding human race.
Many of my correspondents are avid travelers, and they send me photos from around the world. Several of these peripatetic design enthusiasts are as enamored as I am of beautiful bridges, which I consider examples of pure engineering design, or, as the structural engineer, Princeton professor, and structural critic David Billington would term it, structural art. Unlike buildings, which hide their engineering behind architectural facades, bridges tend to lay bare their structural design features. The lines by which forces are directed and transferred are exposed and open to admiration, exploration, and fascination.
Among the most elegant and daring bridge types are the suspension and cable-stayed designs. Suspension bridges are said to have had their origins in hanging vines, but modern examples are made of steel. As high as skyscrapers their towers soar, supporting suspension cables that drape gracefully over, between, and beyond them, held in place by monumental anchorages.
The roadway of such a bridge can appear to be but a ribbon of steel hung from the cables, and in the Akashi Kaikyo Bridge -- Japan’s outstanding example of the genre -- the main span alone stretches over a mile between the towers. The Brooklyn and Golden Gate bridges, the latter of which is celebrating its 75th anniversary this year, are among the most iconic of suspension bridges, and they are truly things of beauty. But my far-flung correspondents have sent me pictures of lesser-known spans that rival even these American designs, and I am always happy to have my vocabulary of bridges expanded.
A more recent type is often confused with the suspension, and that is the so-called cable-stayed bridge. This clever alternative arose in its modern form in the wake of World War II, when the superstructure of many a destroyed European bridge lay in the water beside its piers. It became a design challenge to rebuild on the same foundation a bridge with a superstructure that was lighter than the original but capable of carrying a heavier load of traffic without overtaxing the old foundations. The cable-stayed bridge form that arose has its roadway supported by multiple cables that stretch directly between it and the towers. The multiplicity of cables allows for a wide variety of patterns, thereby giving the bridge designer a greater freedom in establishing a distinctive appearance. This makes the bridge type popular with communities seeking a signature structure. Such aspirations typically include also the goal of attracting tourists with cameras, and indeed they will flock to see and photograph a distinctive new design.
I think Mydesign has an excellent point: ancient engineers built amazing, beautiful structures, many of which have lasted hundreds or thousands of years, without any of today's sophisticated design tools. In fact, many prehistorians are still arguing about just how some of the oldest ones got designed and built, meaning what tools the engineers actually had in the way of mathematics and physical tools such as a string and chalk for laying out some of the more sophisticated megalithic monuments.
I just visited the arch bridge over the New River Gorge in West Virginia, where We went across the bridge on the catwalk below the deck. That is a very interesting tour. It is difficult to grasp the magnitude of the structure until you see it that close up. All of that steel loaded in compression is an awsome thing indeed.
The bridges with structual elements in tesion are also amazing, but it is clear that they require a great deal more attention and maintenance to remain safe, since tensile failure modes are usually much faster than compressive failure modes, at least that is my understanding. It would be quite educational to have an explanation of how corrosive failure of the suspension elements is prevented.
I grew up not far from the Golden Gate Bridge in San Francisco, with a 4,200-foot suspension span built in 1937. Regular painting is done to prevent corrosion, and those paint jobs are the main form of maintenance, according to this site: http://goldengatebridge.org/research/facts.php
Ann, I agree completely. In 2009 my wife and I traveled to Madrid to celebrate our 40th anniversary. While there, we took a side trip to visit Toledo, an ancient city with many extrodanary structures, one being an aqueduct running close to three miles in length. The workmanship was stunning and how the engineers accomplished the uniform downward slope with the tools they had at their disposal amazes me. The stones were all laid by hand, each one carefully placed. Thousands upon thousands of carefully cut and placed stones. I would love to climb into Mr. Peabody's way-back machine just to see how some of these ancient monuments were constructed. It would certainly be a real treat.
I have add in my two cent to this architectural love-fest on bridges. There is something magical about the way they "work" without actually "doing" anything. Sort of like the human equivalent of a spider's web - constantly balancing forces through a series of aesthetic arcs and supports. All in plain view. Thanks for highlighting these marvels of engineering.
Bob, those aqueducts that have lasted 2000-plus years are pretty amazing, aren't they? I've seen lots of good illustrations that show how they work, but none about the exact building methods used. Does anyone else know any?
Ann, our ancient civil engineers and draftsman had done excellent works in designing and building bridges and roads without any analytical and design software/tools. They had used their brain and skills to complete the task, without depending any man made tools. In my country we had a more than a dozen of bridges built by the great British engineers in 19th century. Still most of them are in good condition and public is widely using it and some other are protecting as heritage monuments.
Mydesign, if I remember correctly, you're in India, right? That country has some incredibly well-built, very ancient public structures and multi-story houses in Mohenjo-Daro and Harappa I've read about (and seen reconstructions of), from the Indus Valley civilization of a few thousand years ago. I don't know if they are still standing, fully or partially, but from the archaeological reconstructions I've seen they were both beautiful and well-engineered.
I learned early on that looks are important! Packaging can make the difference between success and failure. Look at the auto industry. Ugly only sells if it's REALLY ugly, otherwise, it's an Edsel.
I looked at the disassembly of the iPad and marvelled at how it was so carefully and artistically put together. It is a work of art and Apple has overflowed its bank accounts.
I am not artistic, but I know how to hire the artistic types and work with them to put things together right. It is worth the money!
Ann, you are right. Whatever the things possible are preserved and keeping as monuments by the archeological department. Apart from Mohenjo-Daro and Harappa, all the buildings with more than 100 years old are preserving by government and archeological departments, irrespective of it's a private or public building.
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