Nuclear piping systems under seismic loading are typically analyzed in two stages:
A transient analysis is performed with a simplified model of the entire piping system to obtain the global response of the system.
Using the global response as the imposed boundary condition, nonlinear static analyses are performed separately on critical parts to investigate local stress and strain responses over time. The critical parts are typically modeled with refined 3–D elements.
This conventional global-local analysis method requires the conversion of results between the global and local models and is usually time-consuming and computationally expensive.
Compared to the straight-pipe segments, curved-pipe bends (elbows) have much greater flexibility and can therefore develop more significant deformation and stresses. Ansys, Inc. elbow element technology offers a simple 1D geometry (similar to a standard pipe element) and excellent accuracy (matching that of a 3D shell element). The elbow can be used directly in both global and local simulation to avoid any cumbersome global-to-local model and boundary-condition conversion.