Various studies have been performed on improving fatigue strength of out-of-plane gusset welded joints because their fatigue strength is low in the case of as-welded condition. Grinding welded joint toes with burr grinder is conventional method for fatigue strength enhancement. In this study, for the purpose of proposing appropriate grinding area for out-of-plane gusset joints, fatigue tests and FEM analyses have been performed.

Slip coefficient of high-strength bolt friction joints is well known to depend on the condition of contact surfaces. As for high-strength bolt friction joints of hot-dip galvanized coating, their contact surfaces have been widely treated by grid blast or phosphate. However, the slip coefficient with grinding treatment friction surfaces of hot-dip galvanized coating is not clear. In this study, the friction type of high strength bolted connection specimens were made on SS400 steel plates, in which contact surfaces are grinding treatment friction surfaces of hot-dip galvanized coating, then slip tests and relaxation tests were carried out on these specimens. On the basis of above examinations, the slip coefficient with grinding treatment surfaces is clarified.

In steel bridge, fatigue cracks are generally detected by magnetic particle test (MT). MT inspection is ineffective and cost consuming compared with other NDT such as eddy current test (ET). The cost reduction and efficiency of inspection can be achieved if fatigue cracks are detected using ET. It is one of the problems for ET that the accuracy of detection at weld zone decreases due to irregular beads noise. In addition, detection reliability of ET is inferior to MT because in ET inspection, inspector judges existence of flaw from change of eddy current signal in complex plane. In this study, the performance of ET was improved by converting detection signals to C-scope image by using position information.