With the increasing need for storage of granular materials a proper approach to the design of silos has become more important than ever. Rigorous methods of design have been hindered by the incomplete knowledge of force actions within the silo during no flow and discharge conditions. Conflicting reports have been quoted in the past as to the difference in conditions set up in the silo during discharge with the result that at the present moment it is still not quite clear whether any provision should be made for dynamic effects produced during discharge. To clarify this situation the author undertook an investigation on a model silo, with sand as the fill material, in which the flow characteristics, the rate of discharge, the pressure distribution on the base and the total load carried by the base and walls, at rest and during flow, have been investigated. The results of this investigation are presented and compared with some of the better-known theories on silos. A new theory is also put forward to account for differences in conditions observed during discharge. D. LENCZNER
The analysis of tanks resting on flat rigid supports is complicated by the non-linear behaviour of the base slab due to the change of support conditions with variations in loading. The partial loss of contact between the floor slab and the rigid support has a critical effect upon the magnitude of the maximum bending moments developed in the tank. Since the principle of superposition is no longer valid the extent of this loss of contact cannot be determined directly. J. D. DAVIES
The contents of the Jubilee Issue of The Structural Engineer constituted a concise review of the evolution of structural engineering during the first fifty years of life of the Institution and included prognostications of future trends, most of which have since proved to be sound. During the five years since this issue was published in 1958 there has been a remarkable upsurge of progress in practically all the fields of endeavour encompassed by our profession. Many ideas and new methods have been brought into or finally established in practice; many others are in process of investigation and development. During the same period there have been radical changes in general and financial policies and other extraneous matters which, though not directly connected with the science and art of structural engineering, have already affected significantly the demands which structural engineers and their associates in kindred professions must be prepared to meet in order fully to satisfy the needs of the community which they serve. F.M. Bowen F.M. Bowen
Mr. J. R. Lowe (Member) said there was a great deal of useful information in the two papers and that he intended to confine his remarks mainly to the engineering applications, rather than to the research work described. He showed illustrations of the Hobart Bridge, which had been the initial cause of the paper by Dr. Rydzewski and Mr. Whitbread (who at the commencement of the work had been in the employment of Mr. Lowe’s firm, E. W. H. Gifford and Partners).
The behaviour of rigidly-jointed redundant trusses when loaded to collapse is investigated both theoretically and experimentally. Trusses which apart from the effect of joint rigidity are singly redundant are considered, and it is shown that their behaviour can be predicted by a method due to Ziegler if the relationships between axial load and axial deformation are known. For a particular set of model light alloy trusses the behaviour under steadily increasing load is predicted using axial load-axial deformation relations for the compression members obtained in a previous series of tests. Satisfactory agreement between predicted and observed collapse loads is demonstrated and the ability of the trusses to carry additional load after buckling of the compression members is also shown. B. G. NEAL and D. M. GRlFFITHS If the relationship between
Dr. D. V. Reddy (Associate-Member) writes that Mr. Rawlings needs to be commended for the generalization of the moment distribution procedure for space frames. The use of direction cosines and matrix formulation of carry-over terms makes the analysis very elegant.