Eiichi Yanagisawa

Magnetostriction Stress Measurement on Dynamic Stress of Bridges and Sensitivity Calibration of Steel Used for Bridges : Applicability of Stress Measurement Technique Using Magnetostriction Effect to Welded Structures (Report 2)

On maintenance of structures, there is a strong need to know stress conditions of steel structure in use. Stress measuring technique using the magnetostriction effect utilizes 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 an experimental study on dynamic stress measurement of steel bridges and calibration of magnetostriction sensitivity of the steel used for bridges. Following results were obtained. (1)By revised magnetostriction stress measuring equipment, dynamic stress fluctuations of steel bridges under real traffic were measured within the accuracy of 95%. (2)Calibration procedures of magnetostriction sensitivity of steel used for bridges were proposed.

Fracture Behavior of Gusset Joint with Plastic Pre-Strain and High Strain Rate.

Fracture tests of gusset welded joint with various conditions, tensile and compressive pre-strain, static and dynamic loading, tension and bending loading, were performed and fracture characteristics were discussed. Ductile fracture strength was estimated using tensile strength of material at tested temperature. Brittle fracture strength was estimated by fracture mechanics using CTOD criteria, CTOD design curve of WES2805 was applied to estimate strain at weld toe of gusset joint. Intrinsic crack model was used to determine effective crack size parameter of gusset joint. Effect of plastic pre-strain and strain rate on fracture toughness was estimated using equivalent static temperature, considering plastic pre-strain and strain rate to temperature shift. Test results of all conditions are well expressed by above estimation method.