Artistic Element in Bridge Design

The Artistic Element in Bridge Design Construction of Highway Spans Becoming Something More Than Mere Problem in Stresses and Strains

IS ARTISTIC bridge design still to be considered a forgotten art in America? Many writers have cited the fact that American designers have been far behind the Europeans in the architectural treatment of bridges.

A few of our great bridge engineers have long recognized this and have insisted upon the necessity for more esthetic treatment. Their work, although confined more or less to those monumental structures which span our great rivers, has helped to promote a desire for the betterment of this phase of the design.

Bridge design is not merely the mathematical calculations of stresses and proportioning of the individual parts, but the consideration of the structure as a whole, its fitness and adaptability to the location and a coordination of the parts into a thing of use and pleasing appearance.

National and city park designers have taken up the problem of the small bridge and have done much towards the artistic development of bridge design. These designers, in co-operation with landscape architects, have attacked the problem from the landscape angle, in attempt to reduce the ugly scars incident to highway construction.

Designer Is Handicapped

In the Western districts of arid lands and long distances, highway locations are made with the thought of the shortest possible line and the least amount of grade and curvature. Under these conditions bridge construction has developed more or less into a means to an end a necessary evil which has to be endured.

The designer has been required to develop structures to fit every conceivable condition of grade and curvature involving skews, super-elevation, adverse vertical curves and, in many instances, a combination of all these in a single structure. Such conditions place the designer under a severe handicap, with respect both to the esthetic and structural solution of the problem. Reinforced concrete has probably been the material most widely adapted to these conditions of curvature and warped surfaces. Combinations of railing is of the pen type of cast-inplace concrete. No attempt was made to embellish the design with plaques and frescoes. The Camp Verde Bridge recently completed by the state is also a series of concrete arches. These four spans of the filled spandrel type required differ-ent treatment from the bridge just mentioned. In this structure the thin arch appearance was materially strengthened by a solid concrete ballistrade. The railing is effectively broken by means of posts and panels.

Steel construction depends to a considerable extent on the development of piers and abutments, especially in small truss spans. Concrete in the approach spans and railings assists greatly in the esthetic effect, as in the Clear Creek Bridge recently designed and built by the Bureau of Public Roads on the Camp Verde-Fossil Creek road.

Small bridges are lacking in mass and depend largely on the railings and dado ends for architectural treatment. In the desert countries very little consideration need be given to the architectural treatment of any part other than that above the roadway, except that symmetry and proportion of span to height should always be considered, and in the majority of cases the correctness of these proportions coincides with the economical aspects. Very rarely, except on curves, does the traveler see other than the roadway elevation; therefore a pleasing combination of railing and posts, combining safety with beauty, at little or no additional cost, is desirable.Beam and girder spans of both steel and concrete, so necessary to the speedy and economical construction of highways, are now being "dressed up" to lessen the scars on the landscape.

Timber construction is more of a problem to the designers, especially the trestle type. Timber is used primarily, and often unwisely, for the reason of economy in first cost; and because of the difficulty of adapting this material to architectural treatment without increasing the cost, very little has been accomplished in this type of construc-piers required to support the concrete arch spans, and the development of the esthetic features was centered around these piers.

Towers Surmount Piers

The abutment piers, necessarily more massive than the rest, divide the spans into groups of 3-4 and 3 and the esthetic effect was obtained without varying the span length. These piers are carried up above the roadway in towers to form a part of the ballustrade. Thesteel and concrete have been used with success.

Spans Are "Dressed Up"

The Tempe Bridge, completed two years ago by the Arizona Highway Department, is built with a reverse curve in the roadway and is a good example of the adaptability of concrete to curvature. In this design, as in many large structures of this type, the writer was able to take advantage of the massive

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