The Vibrating Wire Rebar Strain Meter is used to measure strain in rebar embedded in reinforced concrete by welding it to the reinforcement cage.

A Vibrating Wire Strain Gauge insert is located axially in the center of the instrumented Rebar Strain Meter so that readings are not affected by bending of the Strain Meter. Strain readings are only proportional to the axial load exerted on the rebar. The Rebar Strain Meter is a rugged and waterproof instrument that will survive concrete placement, assuming that the electrical cable is well protected.

Depending on situations, it may be advantageous to install Rebar Strain Meters in pairs or triplets on either sides of the neutral axis of the structure so that bending moment effects can be separated from the axial load. A thermistor is incorporated in the Strain Meter so that temperature effects can be correlated to change of strain in the structure and also monitor the curing process of the concrete.

A Sister Bar application usage is typically a small diameter Rebar Strain Meter which is installed parallel to existing rebar. As its diameter is small, typically 15 mm, it is assumed that it does not disturb in any significant way the strain in the adjacent rebar of much larger diameter. It is therefore assumed that the strain measured in the Sister Bar is equal to the strain in the adjacent rebar and the concrete itself.
The Vibrating Wire Sister Bar is also used as a replacement for Vibrating Wire Embedment Strain Gauges in situations where concrete is poured or cast in ways that could damage the Embedment Strain Gauge, or simply disturb too much their orientation, whereas Sister Bars are more robust and also easier to tie to a rebar cage. Situations where Sister Bars could be preferred to Embedment strain gauges include instrumented piles, tunnel concrete linings and diaphragm walls.

Product features

• Long-term stability in difficult environments
• Waterproof
• Built-in thermistor
• High accuracy and resolution
• Rugged design