Development of Restraint Joints for Composite Steel Pipe and Investigations for Their Performance Evaluation Index

Abstract

Detachment of joints is a common type of seismic damage on pipelines. Restraint joints, which have both flexibility and restraint force against detachment, are expected to be a new method to enhance the safety of pipeline against earthquakes. Prototypes of restraint joints for synthetic steel tube are made and applied to pull-out tests in order to verify their performance in flexibility and restraint force. It is confirmed that the restraint action successfully works in both straight and bent connections of the joints. A cumulative flexibility, which is the total flexibility of joints activated by restraint force, is proposed as a performance index for restraint joints considering both of flexibility and restraint force.