Ritz vector approach for evaluating the dynamic properties of structural systems and incabinet spectra.

摘要

The earthquake input needed in a shake table test for the seismic qualification of safety related electrical instruments, typically mounted on electrical cabinets or control panels, is defined in terms of incabinet response spectrum This dissertation presents modifications to the originally proposed Ritz vector approach developed by Rustogi et al. (1998) for evaluating the dynamic properties of the cabinets and the incabinet spectra. Modifications are needed to overcome the limitations encountered in the application to actual cabinets. The accuracy of the modified formulations is evaluated by comparison of results for actual cabinets with the corresponding results obtained from detailed finite element analyses. The modified Ritz vector approach can account for actual rotational constraints imparted by supporting structural members such as stiffeners. It can also be applied to bench board type cabinets in which instruments are mounted on plates or frames that are inclined to the global axes as well as to frames in which parallel frame members can vibrate in different vibration shapes.; In this dissertation, detailed finite element analyses are used to study the rocking behavior of cabinets and to show that accurate representation of the boundary conditions at the cabinet base is essential in the evaluation of cabinet rocking mode. Simple formulations are developed for evaluating the rocking stiffness in three different types of cabinet mounting arrangements. These formulations enable incorporation of a cabinet rocking mode in the Ritz vector approach.; The Ritz vector approach is also used to develop new formulations for evaluating static and dynamic characteristics of rectangular slabs with edge beams. The effect of elastic edge restraints is considered by including appropriate integrals for edge beams in the expressions for total kinetic and potential energies in a Rayleigh-Ritz approach. The effect of various types of boundary conditions at the beam ends is accounted for by considering the corresponding Ritz vectors. The contribution of beam mass to the total kinetic energy is also considered in the proposed approach.