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Merchant Bridge Deck Truss Replacement

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The Merchants Bridge crosses the Mississippi River north of downtown St. Louis, Missouri. The bridge structure included approximately 450 feet of deteriorating deck truss spans at each approach to the main river spans. Modjeski and Masters was selected to design replacement spans for the existing deck trusses.

The replacement design options were dependent upon maintaining the serviceability of the existing structure during construction, with minimal interruption to traffic. As a result, the new structure was designed as a series of deck girder spans that could be set on pre-constructed concrete bents integrated within the metalwork of the existing deck trusses. This design allowed for an expedited transition from the existing deck truss spans to the new deck girder spans.

Construction parameters required that one track remain in service at all times; therefore, span replacements were performed in two phases. The contractor was allowed one ten-day outage per track to remove and replace the spans. In order to expedite replacement, the deck truss spans were strengthened and removed from under each track, one at a time, to facilitate the placement of the new deck girder spans.


Bridge Geometry
Length of Spans 50 to 98 feet
Total Project Length 934 feet
Tracks on Structure 2