2. Introduction

In order to be able to perform dynamic response calculations of fluid-filled structures to fluids, 3D fluid-structure coupling elements have been developed in*Code_Aster* (cf [bib2]).

These volume elements have the advantage of allowing a detailed description of the structure in particular locations such as, for example, the connection between a main pipe and an instrumentation connection. On the other hand, their systematic use for the analysis of branched and complex networks would lead to prohibitive modeling (mesh production) and calculation costs.

For this reason, and in order to facilitate simplified studies of the dynamic behavior of pipes, an elasto-acoustic straight beam element has been developed making it possible to perform, at a lower cost of manpower and calculation, calculations of the overall behavior of the straight parts of pipes at low frequency.

An overview of the finite elements of elasto-acoustic beam-type pipes is presented below. The vibratory behavior of pipe networks is conditioned by the flow of the fluid that passes through them.