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Abstract

This thesis is concerned with the loads that agricultural materials impose on the walls of their storage structures with special emphasis on grain in the relatively shallow structures found on farms in the United Kingdom.

A review of past work covers the basis of traditional techniques used to calculate wall loads, the ways in which wall loads have been measured, and the results obtained. It is shown that, when compared with calculations using existing design formulae, the results are very scattered. A new stress/strain model for bulk grain is developed which uses four stress dependent parameters to relate shear and normal stresses to shear and normal strains. The model represents the behaviour of the material up to and including failure and includes the effect of shear induced dilation. The parameters for the model can all be measured using suitable tests in a triaxial cell. This stress/strain model is incorporated into a computer program, based on the incremental finite element method, that calculates the stresses within the stored material and at its boundaries.

The design of a silo on which wall loads can be measured is described. Considerable attention is paid to the instrumentation for measuring wall stresses. The effect of size of the sensing area and deflection of the gauge on the measured stress is considered in a theoretical manner and investigated by experiment. It is shown that the measured stress is highly sensitive to gauge deflection and a measurement technique is devised to account for the deflection.

A comparison of loads measured in the test silo with those calculated with the finite element program shows generally good agreement when the wall of the test silo is relatively rigid. The performance of the finite element model in cases where significant wall deflection occurs is however disappointing and further work needs to be done to ensure a more realistic representation of material failure in the computer program.

An appendix compares the void ratio and orientation of the material in the silo with that in a triaxial sample.

Publication Type:	Thesis (Doctoral)
Subjects:	T Technology > TA Engineering (General). Civil engineering (General)
Departments:	School of Science & Technology > Department of Engineering School of Science & Technology > School of Science & Technology Doctoral Theses Doctoral Theses

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