Seismic Stuctural Response of Steam Generators and Their Supporting Structures

摘要

Seismic response studies of two steam generators and their supporting structures were conducted using three-dimensional finite element models. Linear structural analyses of the two systems were performed in two phases. The first involved determining frequencies of free vibration and associated mode shapes. The second involved determining model responses of structural member stresses due to the El Centro Earthquake of May 18, 1940. Twelve natural frequencies and associated modal shapes were determined for each structural system. For the 1200 MW stream generator, torsional modes had to be included in the analysis. For the 600 MW steam generator structural system, the first and second natural modes were predominantly side-swaying motions in two orthogonal directions, while the third and higher natural modes contained torsional motion. Response spectrum analyses furnished quantitative information on shear forces, bending moments, and axial forces for each member of the structure. Maximum stresses and ratios of maximum normal stress to yield stress, and maximum shear stress to shearing yield stress, were obtained for each beam member. Vulnerable components of both models were identified.