CGEO-SG5
Rebar VW Strain Gauge 3
CGEO INTERNATIONAL LIMITED
Installation Manual
1. INTRODUCTION
CGEO-SG5 Vibrating Wire Rebar Strain Gauges are designed primarily for monitoring the
stresses in reinforcing steel in concrete structures, such as bridges, concrete piles and diaphragm
walls. The Strain Gauge is comprised of a length of high strength steel, bored along its central
axis to accommodate a miniature vibrating wire strain gage. Readout of load or stress is achieved
remotely using a portable readout or datalogging system available from Beijing Soil Instruments
Ltd.
The Model CGEO-SG5 Vibrating Wire Rebar Strain Gauge consists of a short length of high
strength steel welded between two long sections of reinforcing bar. It is designed to be welded
between sections of structural concrete reinforcing bar. The cable exits from the Strain Gauge
via a compression fitting. See Figure 1.
Rebar
Strain Gauge Body Strain Gage Electromagnetic Coil Heat Shrink Weld
Rebar
Weld
Thermistor
Compression Fitting
Instrument Cable
900 mm
Figure 1 - Model CGEO-SG5 Rebar Strain Gauge
The Model CGEO-SG5-12 (diameter 12 ) Vibrating Wire Rebar Strain Gauge or "Sister Bar"
consists of a short length of high strength steel welded between two long sections of
reinforcing bar. It is designed to be wire tied in parallel with the structural rebar. The small
diameter of the bar minimizes its affect on the sectional modulus of the concrete. The cable
exits from the Strain Gauge through a small block of protective epoxy. See Figure 2.
Rebar
Strain Gauge Body Strain Gage Electromagnetic Coil Heat Shrink Weld
Rebar
Thermistor
(encapsulated)
Protective Epoxy
Instrument Cable
900 mm
Figure 2 - Model CGEO-SG5 Sister Bar
Both models of Strain Gauges are robust, reliable and easy to install and read, and are
unaffected by moisture, cable length or contact resistance. The long term stability of these
instruments has proven to be excellent.
