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1、Aesthetics in Bridge DesignThe appearance of the bridge is dominated be the shapes and sizes of the elements controlled be the engineer - the structural elements themselves, not by details, color, or surfaces. The Golden Gate Bridge owes its appeal to the graceful shape of its towers and cables, not
2、 to its reddish color. If the towers were ugly, painting them red would not make them attractive.Periodically the suggestions is made that the engineers should delegate responsibility for the appearance of bridge to architects or other visually trained professionals such as urban designers, landscap
3、e architects, or sculptors, the notion being that this would result in better-looking structures. This is rarely successful. The usual result is an overly elaborate and overly costly structure, without a significant improvement in appearance. There are two reasons for this. The first is that the vis
4、ual professional doesnt understand the special limitations and problems of bridge or, even more important, the aesthetic opportunities of modern engineering materials structural types. So, the designer falls back on the familiar conventions of architecture or sculpture and makes something that looks
5、 like a building or a piece of sculpture, not a bridge.The second reason is that the delegation can never be complete. In the United States, engineers have the professional and legal responsibility for bridge. The organizations that commission, finance, and build bridges are usually run be engineers
6、. None of these people are willing or legally able to delegate complete responsibility for a bridge to a nonengineer, no matter how talented. This usually means that the “important” (structural) aspects of the bridge are reserved for the engineers, while the “window dressing” (surface details, color
7、) is left to the visual professional. Although the details are an important part of a structures aesthetic impact, it is the structure itself - its spans, proportions, and major elementsthat has the largest role in creating its effect. If the engineer does a poor job with these major elements, no am
8、ount of architectural add-ons will compensate.Engineer must control the structural elements - that is their job. However, for the bridge to be a complete aesthetic success, the details, colors, and surfaces have to be in tune with the structural concept. Therefore, the engineers should control those
9、 as well. That said, visual professional who are willing to take the time to understand the special nature of bridge can offer a positive contribution to engineers be acting as aesthetic advisors or critics. Their role is comparable to that of other specialists, such as geologists or hydrologists, o
10、n whom the engineer may call for advice. Engineers have accepted a responsibility to society for bridge design. For that reason, no engineer would knowingly build a bridge that is unsafe. For the same reason, no engineer should knowingly build a bridge that is ugly.Aesthetic ability is not some myst
11、erious quality bestowed by fate on a fortunate few. Though many engineers are not well prepares by their education or experience for the visual aspects oftheir responsibilities, they can learn what makes bridges attractive and they can develop their abilities to make their own bridges attractive.Man
12、y tools are available to help engineers improve their abilities in the aesthetic aspect of engineering. Many books present a series of guidelines and the principles that underlie them. It is useful base from which to consider the appearance of structures. But the guidelines are only a beginning. Eng
13、ineers should form their own opinions about what looks good, and work to develop their own aesthetic abilities.Bridges must safely carry their loads for a long enough time to repay the investment made in them. This basic fact imposes a hierarchy on design making:Perfor mancestructural capacity, safe
14、ty, durability, and maintainabilityCostconstruction and maintenanceA ppearanceThat said, this statement often leads to the assumption that three criteria are necessarily in conflict, that one must be sacrificed for the other. This is not true. For example, many people think improved appearance will
15、automatically add cost. They believe good appearance derives from add-ons, like an unusual color, special materials such as stone or brick, or ornamental features. In fact, the greatest aesthetic impact is made by the structural members themselvesthe cables, girders, and piers. These things have to
16、be there anyway. If they are well shaped, the bridge will be attractive, without necessarily adding cost.Many of the greatest bridge engineers were able to create that are beautiful, structurally sound, and less expensive than any alternative, all at the same. In decisions about appearance, as in decisions about strength and durability, the challenge is to achieve an improvement without an increase in cost. It can be done.Now lets discuss the next item on the specific requirem
