Seismic computation of pipes with viscous energy absorbers

Among the possibilities for replacing snubbers in seismic design of pipes, installation of damping systems (viscous energy absorbers or other techno-logical systems, modelled as perfectly viscous in the present study) can be considered. A difficulty then arises in design process: Eigenmodes of the pipe are classicaly assumed to be “uncoupled” (classical damping) ; it is no longer true with located viscosities that create a non classical damping (coupled eigenmodes) . This paper deals with the use of methods of classical damping in this situation of non classical damping.