Micropiles at Merchants Bridge, St. Louis-Video

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Video Summary

The presentation described a seismic and capacity retrofit of St. Louis’s 1890 Merchants Bridge, owned by the Terminal Railroad Association. The 4,340-foot bridge carries traffic for six major railroads and five short lines, but its aging trusses restricted it to one track and lighter railcars; without improvements, it was expected to remain in service for no more than ten years.<br /><br />The project replaced the three main truss spans and strengthened the four original piers. The presentation reviewed the bridge’s historic timber caisson foundations, which remain in use, and the site geology: sandy Mississippi River deposits over relatively level limestone bedrock.<br /><br />The micropile contractor installed 56 piles across the four piers, each designed for 700 kips in compression and 200 kips in tension. Verification tests focused on tension capacity. For the river piers, crews worked from movable platforms supported by sheeted cells, using barges, cranes, and a compact drill. Detailed staging and sequencing helped manage tight access and rapidly changing river levels. After installation, the contractor encased the piers and completed the pile caps.

Keywords

Merchants Bridge

seismic retrofit

capacity retrofit

micropile foundations

river piers

Terminal Railroad Association