Kazuhiro Nishikawa

Retrofitting for seismic upgrading of steel bridge columns

Abstract The purpose of this experimental study is to invetigate methods to improve existing steel bridge piers. In this paper, authors tried to improve the seismic performance of steel column specimens modeling steel bridge piers keeping their ultimate strength. A total of eight specimens, four being rectangular-section columns and four being circular-section columns, were tested under a constant compressive axial load and cyclic lateral loads. The specimens consist of original columns and retrofitted columns. The authors investigated the test result using the energy method. The result shows that it is effective for the rectangular-section column to retrofit corners and for the circular-section column to build the outer pipe keeping a clearance.

STUDY ON THE FATIGUE OF STEEL HIGHWAY BRIDGES IN JAPAN

Abstract Fatigue damage caused by repetitive loading of heavy traffic, especially overloaded vehicles, has been reported in welded areas subjected to secondary or distortion-induced stress. We have been studying the design method of bridges in order to eliminate the existing fatigue problems. This article provides a brief introduction to the current state of fatigue of steel highway bridges in Japan and describes better design strategies to prevent further fatigue damage, based on actual field stress measurements of bridges in Japan.

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 performance-based quality control inspection of welded joints

This study aims to promote rational quality control approaches to fabrication inspection and weld acceptance which together ensure that the structure has sufficient fatigue performance. In order to evaluate the effects of weld defects on fatigue performance, fatigue tests of butt-welded joint specimens of 25, 50 and 75mm thick with various types of weld defects. Acceptable size of weld defects is established from these test results and fracture mechanics analysis. The computerized automatic ultrasonic inspection systems have been developing and the applicability of these systems have been examined through the round robin tests.