Simplified design model for rigid pipe joints based on the two-pipe approximation

Abstract

Solutions for expected shear force and rotation across joints connecting rigid pipes are formulated for use in the structural design of rigid pipe joints and possible inclusion in current pipe standards. The loading system is divided into live loading and earth loading, and these cases are treated separately. Exact algebraic solutions are derived using the beam-on-elastic-spring approximation for two rigid pipes connected by a moment-release joint, which is considered conservative. Additional discussions are also presented about the conservative nature of the “two-beam”-on-elastic-spring approximation compared to finite element solutions for beam-on-elastic-springs problems involving more pipe segments. A parametric study is then presented examining the key controlling factors. Vehicle load calculations assume live load spreading with depth approximated by a trapezoidal loading prism. Earth load calculations are derived for a change in the stiffness of soil support from one section of the pipeline to the next. Comparisons with experimental measurements indicate that the design equations reflect observed changes in joint response as burial depth or pipe diameter increases. Experimental variability is considerable however, and the design calculations are generally conservative.