Yoshima bridge

Yoshima Bridge is a combined road and rail three-span continuous truss bridge. It is located almost in the center of the Seto-Ohashi bridge route which connects the islands of Honshu and Shikoku across the Seto Inland Sea.

The continuous truss design easily adapts to the curved shape of the bridge. Orginally Yoshima Bridge was designed with a 204 meter center span. Constructing the foundations of this span in the sea posed problems of time and cost. The design was revised by increasing the central span to a length of 245 meters, thus locating the foundations on land.

Dead loads (the weight of the bridge elements themselves) were reduced by using HSS for an economical design. The thinner plate themselves and less weight simplified fabrification and construction.

HSS up to HT780 (yield strength of 630N/m²) was used extensively for the main structure. The standard truss chord member is a 1.48 by 1.40 meter box section. The maximum thickness of HT780 steel is 65 millimeters for most truss chord members and 100 millimeters for the bottom plate of chords in the middle pier section.