A Good Foundation
In order to improve the reliability and safety of Structures, structural Health Monitoring (SHM) has become a popular vehicle to determine the condition of the monitored structure and identify potential problems at an early stage. Foil strain gages are widely used in Structural Health Monitoring (SHM) projects and systems because they are inexpensive, easy to install, and very precise and accurate to measure strain. Structural Health Monitoring (SHM) is a catch phrase for monitoring of any infrastructure. SHM can be applied to bridges, buildings, dams, tunnels, wind turbines, industrial facilities, and even light poles.
SHM systems provide accurate and near-real-time information regarding the performance and condition of structures. It will never replace visual inspection and human judgment, but if properly deployed, it can be used to keep a “remote eye” on critical structures. It helps minimize inspection cycles, alerts engineers to any changes, and aids in planning and designing maintenance activities. This increases safety, reduces uncertainty, and lowers operating expenses.
Virtually all manufacturing and fabricating processes introduce residual stresses into the manufactured object. Usually, residual stresses are detrimental, contributing to fatigue and other structural failures that are often unrecognized until after a malfunction or failure occurs. The hole-drilling strain gage method is a relatively simple procedure and has been standardized in ASTM Standard Test Method E 837. The general theory of making residual stress measurements is covered in Micro-Measurements Tech Note TN-503, “Measurement of Residual Stresses by the Hole-Drilling Strain Gage Method”