Statistical inference of unsymmetrical silo pressures from comprehensive wall strain measurements

Abstract

A thin cylindrical shell structure which is subjected to local or unsymmetrical loading often displays a very complex pattern of response, involving multiple alternative potential failure conditions in different parts of the structure. The loading may therefore need to be defined with great precision. In the field of silo structures, it is widely recognised that such local loads often exist, but experimental observations of the patterns of load are very difficult to obtain because of the expense of instrumentation and the need to use full-scale testing to avoid granular solid scale errors. This paper presents a newly developed technique which permits these local unsymmetrical load patterns to be determined in a much more cost-effective way. In addition, because the loading is deduced from the structural response, the method has an inherent robustness in that when the deduced loadings are generalised and used to predict a structural response, it is more likely to be close to the real response. The same cannot be said for loading patterns deduced from single discrete observations of loading with imaginative interpolations between them, which form the basis of most current design rules. The paper describes a rigorous procedure for inferring the complete pressure distribution from a large body of strain observations on the silo wall. The method is outlined and a simple practical example, involving unsymmetrical loads, is used to explore the effect of observation errors on the inferred pressures. A sample set of pressures in a specially built full-scale test silo under eccentric solids discharge is also derived.