The elasto-plastic buckling strength of imperfect hemispheres and their reliability
Başlık:
The elasto-plastic buckling strength of imperfect hemispheres and their reliability
Yazar:
Shao, Wen Jiao, author.
ISBN:
9780438060951
Yazar Ek Girişi:
Fiziksel Tanımlama:
1 electronic resource (224 pages)
Genel Not:
Source: Dissertation Abstracts International, Volume: 76-08C.
Advisors: Paul A. Frieze.
Özet:
The work presented in this thesis aims to investigate the static elastoplastic buckling strength of initially imperfect hemispheres under external pressure and their reliability. It has been pointed out that safety levels for slender and stocky hemispheres are not the same when a constant safety factor approach, as in BS5500, is used in their design. It is lower for slender hemispheres than for stocky ones. This contrasts with the trends apparent in numerical results of the effect of geometric distortions on the strength of hemispheres. To overcome this it seems feasible to derive a formula for the buckling strength of hemispheres which can express the varying influences on the buckling strength of slenderness and deformation amplitude. To this end, a theoretical procedure is presented. A theoretical method for analysing the elastoplastic buckling strength of imperfect hemispheres is described. Dynamic Relaxation (DR) in conjunction with central finite differences is used to numerically solve the doubly-curved thin shell equations and a multi-layer approach based upon the von Mises yield criterion in conjunction with the Prandtl-Reuss flow rule and Whang's technique is used for behaviour in the plastic region. The extension of DR to the solution of non-linear dynamic response analysis in real time is developed. From comparisons with results available in the literature, the shell equations and the elastoplastic constitutive relation given in this thesis can be used with confidence in the study of hemisphere buckling. On the basis of results of preliminary studies, parametric studies are conducted and their results presented. Two strength formulae based upon the results of the parametric studies are derived using modified linear regression. By comparing the results derived from the analysis with experimental data, a formula is derived for predicting the mean of this data based on a slenderness dependent equation for initial deformation magnitude. Because of the lack of statistical data concerning initial deformations in hemispheres, it is necessary to propose a procedure for estimating the statistical parameters for initial deformation amplitude. One is advanced, based on using linear error theory and the information relating to well documented tests on externally pressurised model spheres. Then using these design strength formulae in conjunction with an advanced Level II method, the reliability of imperfect hemispheres is examined. Comparisons of the reliability analysis results with existing codes are made. Results in the form of strength-slenderness curves are derived for three target reliabilities and various load coefficients of variation. A probabilistic interpretation of designs performed in accordance with BS5500 for external pressurised hemispheres is advanced. Conclusions concerning the numerical technique, the parametric studies and the reliability analysis are presented, followed by recommendations for future work.
Notlar:
School code: 0547
Konu Başlığı:
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Yer Numarası | Demirbaş Numarası | Shelf Location | Lokasyon / Statüsü / İade Tarihi |
---|---|---|---|
XX(684863.1) | 684863-1001 | Proquest E-Tez Koleksiyonu | Arıyor... |
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