Abstract: Traditional pipeline design analysis method presented in various literatures is usually based on limit stress criteria,however,the method may be inapposite to modern steels,and the method can not solve all the problems in pipeline strength design,especially for displacement controlled loads such as ground displacement load.Strain limits,including ovalization limit,tensile strain limit and compressive strain limit,are compared in this paper based upon various codes and recommendations.In addition,some control factors of strain limits are also reviewed respectively.In view of the design tendency based on strain and the largescaled construction of gas transportation from west to east,as well as the second level projects,the importance and necessity of the related research are presented.

Key words: pipeline, stainbased, limit state, design criteria, strain limit