Suspended in a harness 30 feet above a concrete spillway in central North Dakota, ITM engineer Ryan “RJ” Matthews instruments the gate of one of the world’s largest earthen dams with dozens of strain gauge sensors.
Integrated Test & Measurement’s field service technicians and engineers have installed strain gauges on civil structures and machinery around the globe for decades, and this project represents one more example of rugged data acquisition. In this instance, the team rappelled from an overhead abutment on the Garrison Dam — a 2-mile-long structure along the Missouri River built by the Army Corp. of Engineers starting in 1947.
Contracted by Cotech IRM Services, ITM was charged with collecting data to measure the strain on one of the 28 spillway gates which are designed to raise and close to allow water to pass from the reservoir during rare flood events. Just behind those gates is Lake Sakakawea, one of the largest man-made lakes in the United States.
Despite the complex location, Matthews and co-worker Zach Strong were able to successfully instrument the spillway gate with 44 single-axis strain gauges and solder signal cables which lead back to a NI CompactDAQ system connected to their laptop, allowing them to successfully gather streams of crucial data using iTestSystem while the gate was put through its paces.
The project is yet another example of ITM’s ability to combine the use of strain gauge sensors, a cDAQ system and the firm’s iTestSystem software to create a structural health monitoring system. In this instance, the project required only one-time testing, but ITM can also establish a permanent structural health monitoring system as well. iTestSystem is an engineering measurement software platform that enables test engineers to organize, acquire, view, and analyze data from machinery, processes, vehicles and other complex systems. iTestSystem was specifically designed for use with National Instruments (NI) cDAQ hardware for data collection and data logging.
For Matthews, it was his first experience installing strain gauges while strapped into a bosun’s chair and dangling in midair, but he points out that ITM’s strain gauge process is essentially the same whether their engineers are standing on a bridge or inside a railcar. All that changes is the method of access and environment.
His field notes reveal that each strain gauge on this job was wired in a quarter bridge configuration, which provides one individual measurement of strain (positive tension or negative compression) per location. All gauges were adhered to the gate using M-bond 200 epoxy. A final report submitted to the customer contained detailed instrumentation and test notes and results reported in a series of stress/strain tables and stress graphs.
Contact ITM for your Strain Gauge Needs
Installing strain gauges in the field for structural and fatigue measurements requires expertise and experience. Whether you use our iTestSystem software to stream and analyze strain signals for static measurements and real-world fatigue data acquisition or contract our software engineers to build a real time strain monitoring system, we will make sure you acquire quality strain data. Contact our strain lab and technicians to install strain gauges on test specimens or to design, build, calibrate, and test strain-based load cells.
Strain Lab Contact Info: Ryan.Welker@iTestSystem.com, (844) 837-8797