# Accession Number:

## AD0651319

# Title:

## NORMAL MODE COMPUTER ANALYSIS OF STRUCTURES.

# Descriptive Note:

## Research and development rept.,

# Corporate Author:

## DAVID TAYLOR MODEL BASIN WASHINGTON D C APPLIED MATHEMATICS LAB

# Personal Author(s):

# Report Date:

## 1967-01-01

# Pagination or Media Count:

## 84.0

# Abstract:

The report describes a computer program which performs the computations associated with the dynamic design-analysis method developed at the Naval Research Laboratory. The program uses the influence-coefficient matrix or stiffness matrix associated with a lumped mass system, together with the masses, to generate the normal modes of vibration and the fundamental frequencies. Of primary importance is the fact that this routine accepts up to 60 degrees of freedom and is generally unaffected by repeated frequencies or frequencies which lie close together. There are capabilities for treating externally redundant systems of certain types, thus alleviating the work of computing influence-coefficient matrices for these cases. Examples of such systems are given. One valuable routine can examine the input matrix of influence-coefficients or stiffnesses and tests for positive definiteness, i.e., whether all eigenvalues associated with the structure model are positive. Furthermore, if the test establishes the existence of negative eigenvalues, then the routine can locate certain areas of the input matrix where errors are likely to be present. Several checks available to determine the reliability of the output are described and examples given. Author

# Descriptors:

# Subject Categories:

- Computer Programming and Software
- Structural Engineering and Building Technology