Development of a unified numerical procedure for free vibration analysis of structures

Abstract : The article presents the details of new numerical techniques developed in connection with the AFOSR grant. Thus a numerical algorithm and a computer program have been successfully developed for the efficient and economical solution of structural eigenvalue problems. Both spinning and nonspinning structures with and without viscous and/or structural damping may be analyzed by the routine. The program fully exploits matrix sparsity associated with the finite and finite dynamics element formulation. In particular, effective solution of the quadratic matrix eigenvalue problem has been implemented for the development of finite dynamic elements. A special symmetric matrix decomposition scheme has been adopted for matrix triangularization that renders the program rather efficient. Also, a novel bisection scheme has been developed that further accelerates the solution convergence rate, particularly for the case of repeated roots. Further, as a special case, the routine solves static problems with multiple load cases. The associated computer program EIGSOL employs an out-of-core solution strategy, enabling effective solutions to be achieved for large, complex, practical structures. A listing of the program written in FORTRAN V for the UNIVAC 1100/82 along with the source deck is available for ready use. (Author)