Estimation of Seismically Induced Longitudinal Strain in Pipelines Subjected to Incident Shear Wave

For buried pipelines, the longitudinal strain is the primary seismic design parameter. The strain can be calculated from a three dimensional (3D) time history analysis. However, performing a 3D analysis in practice can be prohibitive. The objective of the study is to provide guidelines for performing a simplified pseudo-static analysis that approximates the output of a 3D nonlinear analysis. A parametric study is performed to evaluate the degree of influence of numerous variables on the calculated longitudinal strain, the results of which are used to sculpture the guidelines. It is recommended to utilize the outputs from a one-dimensional site response analysis and the closed-form equations to calculate the axial and bending strains of pipelines subjected to a harmonic wave propagating at an incident angle to the longitudinal axis of the structure. To represent a transient earthquake motion as an equivalent harmonic motion, a procedure to extract the pulse that induces the maximum strain considering both the amplitude and the duration is presented. Using the proposed procedure, it is revealed that the reliability of the predicted longitudinal strain is acceptable for design purposes.