MULTIPLY SUPPORTED PIPELINE UNDER SEISMIC-WAVE EXCITATIONS

The dynamic behavior of a surface-mounted pipeline under seismic excitation is investigated. The ground motion is modeled as a superposition of decaying random traveling waves, and the pipeline is modeled as an infinitely long Euler-Bemoulli beam attached to evenly spaced ground supports. Thus, the pipeline is a spatially periodic structure composed of identically constructed units, and it receives seismic excitations through the periodic supports. Damping in the soil as well as the pipeline material is taken into consideration. Closed-form solutions are found for the pipeline response, permitting clear physical insights into the related physical phenomena. In particular, large response is found when significant excitation energy is contained within the wave-passage frequency bands, typical of spatially periodic structures. The most severe response occurs under a coincidence condition when the propagation of seismic excitation matches the propagation of structural waves in the pipeline. This condition is specified in terms of structural and soil properties, and the incident angle between the pipeline and the propagation direction of the surface waves. These theoretical results are fundamentally important and are useful for structural design of surface-mounted pipelines. © ASCE.