GKM installed a new design instrument called cantilever displacement transducer made by Geokon Inc. The sensor is comprised of a vibrating wire strain gage affix under 
a stainless steel blade (cantilever arm). An adjustable rod is connected to the arm and is set on a target whose position is to be monitored relative to the cantilever mounting bracket, as in across a crack. The adjustable rod allows for a low profile floating connection, which can tolerate minor off (z) axis displacements. The cantilever is attached with drop-in anchors and the target is attached with drop-in anchors to the surface.
Several cantilever sensors were installed on a highway culvert crown of 23-m diameter by 210-m long to measure relative displacement (distortion) of construction joint-segments. Rope access technique was utilized for overhanging installations and cable routing to central 
datalogger. Remote monitoring with cellular modem had to be provided due to difficulty to access the site.
The ingenuity of this instrument concept allowing (z) measurements without having to drill large transducer recess in concrete greatly eased the awkward installation.
For additional information, please contact us: info@gkmconsultants.com