A formulation which accounts for fluid-structure interaction of piping system under seismic excitation is presented. The governing equations of the fluid and the structure to model the pipe are stated. Using the finite element method the discretized equations are obtained. A transformation procedure for proper assembly of matrices is introduced. A solution algorithm is described. 9 refs., 2 figs.

This paper presents a comparison of dynamic responses of piping systems subject to independent-support excitation using the response spectrum and time-history methods. The BNL finite-element computer code PSAFE2 has been used to perform all the analyses. The time-history method combines both the inertia as well as static effect on the piping responses due to independent-support excitations at each time point, thus representing the actual responses. A sample problem is analyzed subjected to two independent support excitations and the results are presented in comparison with the response spectrum methods with uniform or independent-support motion.

An analytical study of effects of nonlinearities in piping supports on response to seismic excitation is presented. Response calculations for simplified single degree of freedom nonlinear models are used to illustrate sensitivity to stiffness variations, lost motion and impact damping. Seismic responses of typical spans of various sizes of piping supported by both linear and nonlinear constraints are compared to assess the support load magnifications due to impacting. The idealized nonlinear piping support models are integrated with a finite element model of a large piping system. Time domain seismic responses of the nonlinear piping system are compared to loads determined by a standard linearized seismic response spectra technique.