ABSTRACT
There was much damage in the welding joints of the steel frame building, but there was a little damage of the high strength bolted joints as a result of the earthquake damage investigations. We think with the thing that the adoption of the high strength bolt joints contribute to the improvement of the safety of the steel frame building from these results. If a building becomes larger or taller, the number of the bolts for the joint increases and the bolted joint will be not suitable for building construction. High strength-ization of the bolt solves this problem. If a bolt is made more high strength, the bolt number of the joint decreases as shown in the following figure. But the risk of the delayed fracture is entailed for higher strength of the high strength bolts. The development of the super high strength bolt which delay fracture doesn’t occur in was begun by my proposal in Nippon Steel Corp. in 1989. We succeeded in the development of the super high strength bolts about five years ago, and started to use them carefully this year. This paper introduces the summary of the result of the examination about delayed fracture of these bolts. https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780203758984/c550ef7c-0737-4c63-849c-b4916ca77624/content/page_339.tif"/>
