Due to concerns regarding the soft nature of the bridge abutment foundation soils and the proximity of construction relative to the old bridge a geotechnical/structural instrumentation program was implemented to provide monitoring of the construction impacts. Automated measurements were taken of 19 vibrating wire piezometers monitoring water pressures in the foundation soils beneath both sides of the river, a vibrating wire piezometer which recorded river water levels, and two vibrating wire strain gages which monitored impacts on the existing bridge. Manual measurements were taken of tilt plates installed on the old bridge, settlement pins placed in the fill and inclinometers installed in the foundation soils.

We were tasked with designing and fabricating the 2 automated monitoring systems, one for each abutment embankment. The systems had to be battery powered with solar re-charging. We utilized our VWDSP Interface to provide high reliability vibrating wire measurements, along with our lightning protectionequipped MultiMux, and Campbell Scientific CR800’s to automate the measurements. The systems were also equipped with cellular IP modems to provide remote telemetry. A view of an installed system is shown.

Data were automatically collected every hour and imported into the MLDB database. Our MLWeb software was used to provide web data access to the construction contractor and owner. Use of MLWeb also provided for entry, via web forms, all of the manually read instrumentation data. Data were entered via the Add Data form, and were reviewed and edited using the View Data and Edit Data forms. The entered data were then made immediately available for generation of the settlement and tilt plots.