Rapid, Portable, Non-Contact Modular Sensor for Surface Strain Measurement for Industrial Diagnostic Testing

Structural design considerations are dependent upon deformations due to applied forces in concrete members, most often determined by transfer lengths. The current method of adhering stainless steel discs and measuring surface strain via a mechanical strain gauge in prestressed concrete is time consuming, tedious and cannot be performed on a production basis. Further, the current method is subject to considerable human judgment and/or errors and often don’t provide for accurate and actual tension release times.

Researchers at Kansas State University have developed a rapid, portable, noncontact, modular device for measuring surface strain that can be used for industrial diagnostic testing. Applications include laboratory as well as field measurement capability, the determination of transfer lengths on prestressed concrete beams and panels, and the monitoring cracks and deformations in bridge structural members. The device may be configured in a variety of ways by integrating two or more of the individual optical sensor modules into a single spatially arranged sensor assembly with the modules rigidly attached to one another. This device generates and digitally records high resolution laser speckle imaging patterns at various points along the prestressed concrete member to determine surface strain. Also included in the design is the ability to incorporate natural or artificially introduced features to act as a tagging system for surface movement. This device was verified against results obtained using traditional mechanical as well as electronic surface mounted strain gauge techniques, as shown in the figure, and proves to eliminate human bias while improving accuracy.

ADVANTAGES:

• Flexible modular design
• Higher accuracy
• Ability to implement on a production basis
• Manual or automated versions
• Minimal setup required, doesn’t require extensive operator training
• No alternative device currently exists to perform diagnostics for railroad crosstie manufacturing

• 1D and 2D strain diagnostic testing
• 1D and 2D strain field management
• Bridge crack monitoring
• Quality Assurance of concrete railroad crossties during production

• U.S. patent #8,917,384 issued on December 23, 2016