NON-LINEAR SEISMIC ANALYSIS OF BATTERY ASSEMBLIES MOUNTED ON RACK SUPPORT

摘要

As part of plant maintenance and upkeep, commercial nuclear plants routinely perform walkdowns of various structures and equipment to identify and correct any potential anomalies associated with installation and/or maintenance. One of the objectives of such walkdowns is to look for findings associated with the as-installed conditions, which may be different from intended design. The intent of these walkdowns is to increase the reliability of the plant. A typical finding associated with these walkdowns, is identification of excessive gaps for equipment and support structures. For example, one such finding is identification of minor gaps at either end of battery assemblies with respect to supporting racks, making it slightly different than their design basis configuration for seismic qualification. As such, the battery assembly is liable to rattle inside the battery rack causing sliding and impact loads onto the batteries and the supporting rack members. For the as-found condition, non-linear seismic analyses were performed to obtain realistic reaction loads and determine the extent of sliding and separation (uplift) of the battery assembly with respect to the supporting racks. These analyses properly modelled the exact gaps found on either end of the assembly, as well as non-linear base interface conditions for the possibility of sliding and uplift of the batteries, before the supporting racks were engaged. Another objective of the analysis was to develop In-Equipment Response Spectra (IERS) for comparison of the as-designed condition (no gaps) with as-found condition (with gaps), in order to determine the impact of gaps on IERS, and thus the battery seismic qualification.