The work reported here is directed towards the problem of measuring and modeling non-linear damping in steel space frame civil engineering structures. In order to gain a better understanding of the damping mechanism in such structures, tests were performed on a full scale bolted lattice structure and the results of section A show that the joint damping can be represented approximately in the form: FD = C (1 + ε |ẋ|n)ẋ where n=1. Other situations. where this form of non-linear damping occurs is in the case of fluid flow past a solid body. In offshore structures the hydro-dynamic force due to drag effects are found to be proportional to velocity squared. For non linear material damping, n, takes a value of 6. In section B, various methods of solution to the non-linear dynamical system under random excitation were studied and it was found that the Equivalent Non-Linear Differential Equation (ENL) method yields a better measure of the response of the non-linear system to white noise excitation than other approximate methods. Analytical expressions are derived for the mean-square response, probability density function and level crossing rates. With the modified ENL method (MENL) it is shown how one can extract the non-linear damping and excitation power spectral density. A good correlation is obtained between experimental and theoretical results.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:456099 |
| Date | January 1978 |
| Creators | Gabri, B. S. |
| Contributors | Kirk, Colin L. |
| Publisher | Cranfield University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://dspace.lib.cranfield.ac.uk/handle/1826/3567 |
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