An automated structural monitoring system for the Federal Reserve Bank of Boston

Among the burdens of massive underground construction programs in urban areas is guarding public safety and protecting building owners' property. This paper describes a unique monitoring system installed for the Federal Reserve Bank of Boston (FRB), and explains the decision-making strategy in the case of unplanned consequences of underground excavation nearby The FRB building, a 21-year old, 33 storey facility, stands immediately adjacent to the 34 m (110-ft) deep, open-cut 1-93 construction of Boston's Central Artery on Atlantic Avenue. Each of the Central Artery Tunnel's prime construction contracts provides for geotechnical and structural monitoring of its own highway segment as construction proceeds, assessing and assuring that ground movements remain within anticipated range and construction components are not overstressed. The structural monitoring of the Federal Reserve Bank's foundation has been the responsibility of a team gathered in 1993. As a part of this team, the CTL (Construction Technology Laboratories, Inc.) structural health monitoring specialists designed and installed a 500-sensor system utilizing automated data acquisition/communication focused specifically on protecting the needs of this facility, and fully integrating it with the geotechnical monitoring program. The automated system consists of more than 300 strain gages on building components monitored continuously. All strain gage data is pre-processed by the system's central computer and resolved into meaningful parameters such as column bending strains, and automatically compared against predetermined specific response thresholds. These were devised to reflect anticipated impacts on the structure at each individual stage of the construction process. Active data communication links connect the Bank's operations staff, the CA/T project managers, the contractor and system operations staff at the CTL Structural Laboratory in Chicago.