Merchants Bridge Renovation
TRAA Merchants Bridge is a rail bridge that crosses the Mississippi River between St Louis Missouri and Venice, Illinois. First opened in 1889, the bridge is owned by the Terminal Railroad Association. It services six Class 1 railroad companies and Amtrak.
In 2018, work began on an extensive renovation of the bridge. The $172M project includes the replacement of the eastern approach and the three main spans of the bridge. Since the bridge is one of only two rail crossings within the TRAA network, the construction sequence has been designed to minimize disruption of rail traffic.
Strong magnets held tiltmeters securely to the bridge.
GEO was tasked with monitoring for construction-caused movement that could impact the safety of passing trains. The objectives were:
- Obtain baseline data to characterize the pre-construction behavior of the bridge.
- Monitor any movement of the structure during construction.
- Provide easy access to real-time data.
- Broadcast alerts to smartphones and PCs if alarm conditions are detected.
GEO initially proposed a solution using AMTS and prisms. However, the contractors opted for a less expensive option using a node-and-gateway data acquisition system consisting of 31 battery-powered tiltmeters, 4 solar-powered internet gateways, and GeoCloud services for processing alarms and generating graphs and reports.
The tiltmeters were installed down the centerline of the piers and bents. Some can be seen above.
GEO fit the biaxial tiltmeters with magnetic mounting plates and installed them on each of the river piers, the eastern approach trestle bents, and the abutments. The gateways were installed at equal distances along the the bridge to a robust wireless network.
The tiltmeters were configured to transmit measurements to the gateways at 5-minute intervals.. The gateways relayed the measurements to the GeoCloud servers.
The servers checked incoming data for for alarm conditions and then posted results on a dedicated project website.
Forty feet up in a manlift on a cold day.
GeoCloud automation provided significant cost savings by eliminating the thousands of feet of cable normally needed for traditional tiltmeters and data loggers.
GeoCloud services run 24/7. Current data and graphs are always available to PCs and smartphones just minutes after measurements are recorded, and alarm notifications, if any, are automatically sent to selected stakeholders.