Abstract
On maintenance of structures, there is a strong need to know stress condition of steel structures in use. Usually, strain gauges are used for stress measurement, but they can measure stress fluctuation only after pasting them to structures. So, stress already existed in structures beforehand cannot be measured. Stress measuring technique using the magneto-strictive effect senses magnetic field distortion by strain of steel itself. It has a possibility to measure stress already existed in structures beforehand, such as dead load stress or welding residual stress. We made experimental study on measuring stress in steel bridges using the magneto-strictive effect, and the following results are obtained. (1) Stress measuring technique using the magneto-strictive effect can measure stress in steel plates which have the same surface condition as that used in steel bridges. (2) The magneto-strictive effect has a possibility to measure welding residual stress in ‡T girder of steel bridges. (3) By using the magneto-strictive effect, it is possible to measure stress in steel with 200 μm thickness paint and to measure stress change of steel bridges during erection
