8.6. Analysis and Solution Controls

8.6.1. Modal Analysis of the Global Piping System Model

A prestressed (PSTRES) modal analysis is conducted on the global model.

Initially, a large-deflection (NLGEOM) static analysis is performed, followed by the prestressed modal analysis (PSOLVE). The Block Lanczos solver (MODOPT) extracts the first fundamental mode.

PSTRESS,ON
MODOPT,LANB,1  
MXPAND,1, , ,0
PSOLVE,EIGLANB

To examine the effect of the prestressed analysis, a modal analysis without prestress effects is performed on the same model, as follows:

MODOPT,LANB,1  
MXPAND,1, , ,0
SOLVE

8.6.2. Nonlinear Static Analyses of the Local Elbow Models

A nonlinear static analysis is performed on both of the local elbow (ELBOW290 and SHELL281) models.

A constant time increment of 5 ms is specified to obtain the stress and strain response over a period of 20 seconds.

Large-deflection effects are included.

Results are stored (in the RST file) for all substeps.