Analysis of Mainframe Computer Structures Using Implicit and Explicit Finite Element Analysis

Abstract

Abstract This paper discusses the finite element analysis (FEA) methods used to analyze the performance of a mainframe computer’s structural frame under a standard seismic loading such as that defined by Telcordia NEBS Zone 4. Specialists in the earthquake robustness area need to consider the basic mainframe structural information such as the total mass and the center of gravity in order to properly size and install tiedowns to prevent tiedown failure which can lead to hazardous tip-over events. To ensure successful operation through a seismic event, the total deflection of the top of the mainframe is a good indicator of ensuring the mainframe computer’s continuous operation. As the mainframe computer’s total weight and the center of gravity varies depending on the specific customer configuration, this paper will examine the two extreme end cases: the lowest mass configuration with the highest location of the center of gravity and the highest mass configuration with the highest center of mass location. From a structural perspective, the higher the initial resonance frequencies, the more rigid the structure and the smaller the upper frame deflection will be. Thus, given a mainframe structure, the finite element analysis results will provide information on the weakest direction resonance frequency, which is in the narrow, side-to-side direction, along with the mainframe rack tiedown loads and maximum top frame deflection. Given a mainframe structure’s finite element model and standard time domain seismic acceleration input at the base of the frame structure, the explicit finite element method will provide the performance of the structure namely the first resonance frequency, the maximum stresses at the rack structure, load at the tie down locations and the maximum top frame deflection. The explicit finite element analysis model can take into account the non-linear contact regions around weld areas and between adjacent sheet metal frame components as well as material non-linearities. The result of the FEA analysis of the several mainframe configurations will be compared to the results from actual seismic earthquake mainframe tests.