Hiromi Shirahata

Performance Evaluation Test of the Time-of-Flight Diffraction Technique for Welded Joints of Steel Bridges

Ultrasonic testing can be applied to welded joints of steel bridges following a revision of the Japanese Specifications for Highway Bridges. The time-of-flight diffraction (TOFD) technique and the pulse echo technique are possible testing methods. However, the efficiency of the TOFD technique for steel bridges has until now not been investigated completely. A round robin test project using testing systems of several different companies was organized by the Ministry of Construction for this purpose. The performance of each participant system was evaluated and applicability of the TOFD technique was investigated.

Fatigue crack detection by the use of ultrasonic echo height change with crack tip opening

There have been reports on fatigue cracking of steel bridges, especially old bridges such as constructed in the 1970s. At that time, less attention of weld quality was paid. Weld defects of the poor quality of welded joints can be crack initiation points. Judgment whether a fatigue cracking occurs or not from a weld defect is very important in terms of appropriate maintenance work under limited time and cost. This study aims at discriminating between fatigue crack and weld defect by ultrasonic nondestructive test. During fatigue crack growth, the opening phenomenon is known. Crack tip displacement increases according to the loading level. That can be observed by the echo height. Cruciform specimens of double bevel welded joints were prepared. Each of the specimens had an incomplete penetration by remaining root face. Tensile force was applied to the specimens. During loading, the ultrasonic instrumentation was set up and echo heights were measured. By the subtraction of the images between loading and non-loading conditions, the tip of a crack was localized successfully.

A STUDY ON CHARACTERISTICS OF ECHOES FROM PLANAR DEFECTS BY THE ULTRASONIC TESTING OF ANGLE BEAM TECHNIQUE

The application of field-welded butt joints of flanges and web plates for steel girder bridges has been on the increase in Japan. Figure 1 is an illustration of such a field-welded joint. The thickness of the flange plate may at times be in excess of 75 mm. Radiographic testing has been used to inspect the quality of welded joints in the shop; however, taking into account material having a thickness that is beyond the capacity of the radiographic testing and the risk of using X-rays in the field, ultrasonic testing is applied to field-welded joints [1,2].

A STUDY ON DYNAMIC RESPONSE OF BRIDGE CAUSED BY LOADS IN LINE AT HIGH SPEED BY BOUNDARY ELEMENT METHOD

高速列車が橋梁を通過する際に生じる問題の1つに衝撃荷重がある. 今後さらに列車を高速にする計画があるが, 従来のモード法をベースにした解析法によれば, 高速域で, 衝撃率が極めて高くなることもある. 本研究では従来あまり試みられたことのない移動荷重による橋梁の動的応答を弾性波動から検討する目的で, 境界要素法を用いた解析を試みたものである.