PURPOSE: To lighten the whole, and facilitate construction, by composing the whole device that consists of footboards, receiving beams, attachments, posts, and rails of an aluminum alloy material to form footboards in a rigid-frame structure. CONSTITUTION: All members such as footboards 4, receiving beam 5, attachments 6, posts 7, and rails 8 that compose a device are manufactured of an aluminum alloy material, and are formed in a structure assembled in the field. Longer members such as the footboards 4, the receiving beams 5, the posts 7 and the rails 8 are molded by extrusion molding, and the footboards 4 are formed in a rigid-frame structure having diagonal members 9. Herewith, the weight of the device is reduced to prevent stress resultant of bridge main body from increasing, and rusting can be prevented easily.
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