Thrust Restraint of Buried Pipelines Subjected to Internal Pressure, Thermal, and Earthquake Loads

Abstract

This paper presents an analytical solution for thrust restraint analysis of buried pipelines subjected to internal pressures and thermal and earthquake loads. The proposed analytical solution is modified from the current approach, which does not include the effect of temperature or earthquake loads or the complexities of pipe–soil friction nonlinearities resulting from change in the direction of relative pipe-to-soil motions. The proposed analytical solution is validated using a finite-element model that accounts for longitudinal pipe-to-soil friction and soil stiffness against transverse movement of the pipe. This paper also includes two case studies using the approach presented in this paper: one is a steel pipeline with a 5.4-in. (0.137-m) diameter and a 45° bend in a nuclear facility subjected to high internal pressure and high temperature loading, and the other is a prestressed concrete cylinder pipe with a 72-in. (1.83-m) diameter and a 45° bend subjected to internal pressure and temperature and earthquake loads. Both case studies suggest that the demands on the pipe segments adjacent to the pipe bends are greater when we include temperature and earthquake loads. In addition, this paper also shows that the sequence of load application of temperature and earthquake loads may result in changes in the direction of friction along the length of the pipeline, which affect the internal forces in the pipeline. This paper presents a procedure for analysis of pipelines where a change of direction of friction is likely.