Monitoring During the Unbraced Network Tied-Arch Bridge Construction Using ABC Techniques

A unique network tied-arch bridge with free-standing arches was designed to carry the 2 nd Avenue traffic over the Interstate (I) 94 in Detroit, Michigan. This 245-ft-long, 96.5-ft-wide, and 18° skew bridge is the first skewed unbraced network arch bridge in the United States. The skeleton of the superstructure was erected off-site at a bridge staging area and moved and placed over the I-94 freeway using self-propelled modular transporters to complete construction. Based on the observations from the analysis models and the communications with the Michigan Department of Transportation, the Engineer of Records, and the peer review engineer, an instrumentation system was designed and installed in the bridge to: (i) monitor and record strains in major components during construction to determine the state of stress after construction; (ii) monitor and record the change in strains during service life to support bridge maintenance and load rating decisions; and (iii) collect adequate data to verify design assumptions. This paper discusses instrumentation system planning, design, and implementation, including sensor locations, data acquisition systems, cable and power management, data collection, and observations. The instrumentation system functions as expected. The monitoring data confirm that the structural component strains are within the design limits and the structure functions as expected.