The steel box girder bridge is depicted in Fig. 4.10. The steel elements are fabricated and erected as “tubs,” and the composite concrete deck is placed in the field. This configuration has some advantages over plate girder construction. Visually, it is “cleaner,” and it does not provide surfaces for birds to perch. For high-visibility bridges, such as urban interchange bridges where motorists are constantly passing beneath the bridge, the enhanced appearance may be a deciding factor. Also, the cleaner surface areas tend to improve durability and reduce repainting costs. The bridge is torsionally stiff—especially
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FIGURE 4.10 Cross-section of bridge with steel box girders. |
beneficial for horizontally curved bridges. These advantages come at a price, however, because box girder bridges are generally more expensive than plate girder bridges. Sometimes the extra cost is knowingly borne for the aesthetic advantage.
