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only. The purpose of the tapping is to relieve any local stresses induced by
the welding procedure.
9.
After tapping four or five times on each gauge end, read the gauge.
Continue the tapping procedure until the readings have settled down and
are not changing more than a few digits.
All readings are referred to an initial reading; therefore, it is important that this
initial reading be taken carefully. It is preferable to install gauges on steel
members that are still in an unloaded condition, i.e., prior to their assembly into
the structure. In this way, the initial readings correspond to zero load. Otherwise,
the initial readings will correspond to some unknown load level.
Record the ambient temperature at the time of each reading, along with notes
concerning the construction activity that is taking place. This data might supply
logical reasons for observed changes in the readings. For temperature
correction factors when used on concrete, see Appendix D.
4.2.7 INSTALLING THE PLUCKING COIL HOUSING (MODEL 4100 ONLY)
Remove any masking and place the plucking coil housing over the gauge.
Connect the gauge to the readout box and adjust the housing until a steady
reading is obtained. In this position, use the spot welder to weld the tabs holding
the coiled housing to the substrate.
Next, protect the tabs and surrounding bare metal from corrosion as described
in Section 3.4.
4.2.8 INSTALLING THE GAUGE COVER (MODEL 4150 ONLY)
provides the 4150 with a semicylindrical metal cover. Spot weld the
GEOKON
cover in place over the gauge as shown in the figure below.
Next, waterproof the spot-welding tabs as described in Section 3.4.
FIGURE 18: Spot welded Cover Plate
4.2.9 SECURING THE 4150 GAUGE CABLE
Using the shim stock provided, spot weld the cable to lead wire junction firmly
to the steel substrate. Be sure to leave some slack in the lead wires. Using
another piece of shim stock, spot weld the cable to the steel substrate,
approximately 25 mm (1") behind the lead wire junction.
4.3 INSTALLING THE 4100/4150 VIA EPOXY BONDING
Note: Due to the large number of variables associated with adhesive (thermal
cycles, UV exposure, vibration, impact, moisture, corrosion of base steel, etc.),
use epoxy cement for short term monitoring only.
Use the following tools and accessories to install the 4100 or 4150 onto steel by
epoxy bonding:
■
Power grinder or sander, files, wire brush, sandpaper
■
Quick-setting two-part adhesive, such as Loctite 410 with accelerator
MODEL 4100/4150 SERIES VIBRATING WIRE STRAIN GAUGES | GAUGE INSTALLATION | 13
18:
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