sensors

VW Rosette Strain Gauge

Multi-axis strain gauge assembly for determining the magnitude and direction of principal stresses in concrete.

Model No
G77-V200R
Configurations
3-element or 4-element Rosette
Angular Spacing
45° / 90° / 135° (Standard)

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Overview

Multi-axis strain gauge assembly for determining the magnitude and direction of principal stresses in concrete.

The Geolook Vibrating Wire Rosette Strain Gauge is a specialized assembly used to measure strain in multiple directions at a single point. In most structural monitoring, sensors are placed in a known direction of stress; however, in complex structures like dam abutments or tunnel intersections, the direction of maximum stress is often unknown. The Rosette consists of three or four G77-V200E strain gauges mounted on a precision frame in a fixed geometric pattern (typically 45° or 60° intervals). By measuring the strain on all axes simultaneously, engineers can mathematically calculate the principal strain magnitude, the principal stress direction, and the maximum shear stress at that location.

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Benefits & Features

  • Measures multi-directional strain at a single coordinate
  • Fixed geometry frame (45°, 60°, or 120° configurations)
  • High-precision VW elements with excellent stability
  • Includes multiple thermistors for localized temperature mapping
  • Ruggedized for direct embedment in mass concrete
  • Essential for complex 3D stress-state analysis
  • Frequency output remains stable over long distances

Detailed Description

The Need for Multi-Axis Monitoring

In simple beams, we know the stress is longitudinal. In a massive 3D structure like a dam, the stress can come from any direction. A single strain gauge only 'sees' movement along its own axis; it is blind to perpendicular forces.

The Rosette Strain Gauge (G77-V200R) provides the data required to perform a full tensor analysis. This allows engineers to identify if the structure is twisting or shearing in ways that a linear gauge would never detect.

Geometric Accuracy

The accuracy of a stress-direction calculation depends entirely on the accuracy of the angles between the sensors. Our Rosette frames are CNC-machined to ensure the gauges are held at exact 45° or 60° intervals during the concrete pour.

This rigid internal skeleton prevents the gauges from shifting or tilting under the weight of falling concrete or the vibration of industrial pokers during installation.

Calculating Principal Stresses

Using the readings from the three sensors (εa, εb, εc), the Geolook software or the engineer can solve for the three unknowns: the maximum principal strain (ε1), the minimum principal strain (ε2), and the angle (θ) of the stress axis.

This information is vital for comparing real-world structural behavior against Finite Element Method (FEM) computer models used during the design phase.

Thermal Mapping

Each sensor in the rosette contains its own thermistor. Because the sensors are slightly separated in space within the rosette frame, this allows for highly localized temperature gradient mapping, further refining the accuracy of the strain-to-stress conversion in mass concrete.

Available Models

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Specifications

Model No
G77-V200R
Configurations
3-element or 4-element Rosette
Angular Spacing
45° / 90° / 135° (Standard)
Range
3000 µε per element
Resolution
1.0 µε
Material
Stainless Steel & Rigid Mounting Frame
Protection
IP68