Swiss Cheese Box Girders

by Pierre Richard, Dir. of Research and Development; Bouygues Group, Paris (Cedex), France,

Serial Information: Civil Engineering—ASCE, 1988, Vol. 58, Issue 3, Pg. 40-43

Document Type: Feature article


Now going up in the French Alps, the Sylans and Glacieres viaducts have decks supported by three-dimensional arrays of concrete trusses. The superstructures look like concrete box girders with holes punched in their webs. This design cuts dead weight, permitting longer box-girder spans, which in turn cut costs because the pier foundations are expensive. It also permitted deeper boxes, cutting the amount of post-tensioning tendon needed. The superstructure was erected without a midspan closure pour, by erecting as one, two half-spans 8 in. to the right of their ultimate location, and sliding them 8 in. to the left into final position. The author recommends, on future projects, three changes which he predicts would cut costs, making the design still more competitive, yet not jeopardize function. They are: eliminate epoxy at the joints separating the precast segments; switch from multi-wire tendon to single-strand tendon in the X-shaped web pieces; and permit segment-joint opening at the ultimate limit state.

Subject Headings: Tendons | Box girders | Concrete | Superstructures | Foundation design | Viaducts | Decks | Trusses | Alps

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