What is a defining feature of a steel box-girder bridge?

A defining feature of a steel box-girder bridge is that it has web plates connected to a single bottom flange. This design allows for a strong and lightweight structural system, as the box shape creates a closed cross-section that enhances resistance to twisting and bending under load. The combination of the web plates and bottom flange contributes to the overall strength and stability of the bridge, making it particularly suitable for longer spans and a variety of load conditions.

Additionally, the box-girder structure is advantageous for both straight and curved alignments, allowing for greater flexibility in bridge design. The closed section provides a stiff and efficient structure that can adequately handle vehicular loads while maintaining a manageable weight.

Features like the absence of internal stiffeners are not defining characteristics of box-girder construction, as many box-girder designs do include internal stiffeners to enhance structural integrity further.