C.J. Brown

Silos. Fundamentals of theory, behaviour and design

Foreword Part 1: Silo Flow. Part 2: Concrete Structures. Part 3: Metal Structures. Part 4: Numerical simulation of particulate solids. Part 5: Silo Tests. Part 6: Experimental Techniques. Part 7: Research for Industry. Index.

Intramedullary femoral nails: one or two lag screws? A preliminary study

Failures of proximal femoral nails that treat unstable femoral fractures have been reported. In this communication, a finite element model to include a proximal femoral nail within a fractured femur was used to carry out preliminary investigations into configurations of single or double lag screws. The effects of the different types of fracture were investigated. The results show that in order to share the load evenly between two lag screws, a good configuration seems to be to have a slightly larger screw above the lower screw. This also ameliorates stresses in the nail at the lag screw insertion holes. However, using two screws in this way can lead to large stresses in the cancellous bone in the femoral head, and these stresses may be significant in the initiation of cut-out.

Elastic buckling of plates with eccentrically positioned rectangular perforations

The conjugate load/displacement method is used to analyze square plates with perforations, and results are presented for geometries with rectangular holes offset from one or both axes of symmetry. Results are given for uniaxial and shear loading, and simply supported and fully fixed boundaries. Design guidance for the location of perforations and the effect of longitudinal or lateral slots is explained. The potential to increase the elastic critical load for an unperforated plate by the introduction of a small perforation is reported.

The elastic stability of square perforated plates under combinations of bending, shear and direct load

Abstract This paper presents solutions for the elastic stability of plates containing perforations using the conjugate load/displacement method. Interaction curves for a variety of load cases and support conditions are presented. The effect of the size of a central square hole in a square plate on the elastic buckling load is demonstrated and, where possible, results are compared with the work of other authors.

The elastic stability of square perforated plates

Abstract A direct matrix method of analysis for the buckling loads on structures, which had already been proven on various structural forms, is applied to the examination of the stability of flat square plates with central square perforations. The results for a variety of boundary conditions are presented for a range of hole to plate size from 0 to 0.8. The method generally shows trends which are different to those predicted by other numerical methods, particularly over the range of the larger hole sizes. Possible reasons for these differences are suggested, but further work to obtain definitive results is clearly needed by all investigators.

Experiments on a square planform steel silo

Rectangular planform silos have not been studied as often as their circular counterparts, and relatively little detailed information exists in the literature on pressure patterns which develop on their walls. This study used a pilot-scale square planform funnel flow unstiffened steel silo with relatively flexible walls to investigate the patterns of pressures on filling, during storage and during discharge. Two different free-flowing solids, sand and pea gravel, were used. The silo was instrumented with wall pressure cells, free field cells, strain gauges and displacement devices. From the extensive collected data, some examples of measured pressures during filling and discharge are presented, together with an introduction to the effects of eccentric discharge.

Patterns of wall pressure on filling a square planform steel silo

Abstract This paper reports the filling pressures measured in a rectangular planform silo with flexible walls. Many experiments were conducted on a pilot-scale square unstiffened steel silo with a pyramidal hopper. The stress state in the solid stored in the silo was thoroughly investigated during filling using both wall pressure cells and free field pressure cells. The results show that the pressure distribution at any given depth at the end of filling may be far from uniform, though most existing silo pressure theories and design codes assume uniformity in any horizontal plane. High pressures were found to develop in the corners of the silo, with corresponding lower pressures at the centre of the walls. An explanation is offered for the observed pressure pattern and a design proposal is made.

The elastic stability of square perforated plates under bi-axial loading

Abstract A direct matrix method for the buckling loads on structures is applied to the examination of the stability of flat square plates with central square perforations under various combinations of bi-axial loading. Results are given for a range of hole to plate size from 0 to 0.8. The method generally shows results comparable with previous work and highlights interesting effects when one component of the bi-axial load is a high value of tension.

GPS monitoring of a steel box girder viaduct

Structural performance monitoring of bridges has increased as major infrastructure ages and is required to sustain loads that are significantly greater than those predicted during design. Structural stiffness and/or mass distribution can change over the lifespan of a bridge structure. Resulting changes in profile or resonant frequency provide key indicators of change, and may identify structural defects. Field tests using GPS for monitoring relatively small deformations were carried out on a steel box girder viaduct bridge in the UK. The configuration consisted of five GPS receivers located at key locations on the viaduct and two reference GPS receivers. GPS data was collected at either 10 Hz or 20 Hz and post-processed using proprietary software, along with appropriate filtering and spectral analysis. Three main frequencies were clearly detected by the GPS in the vertical component. A previously reported frequency of approximately 0.56 Hz was identified along with two other frequencies. The peak vertical deflections lie in the range of ± 50 mm, while lateral and longitudinal deflections of much smaller magnitude – in the order of a few mm – are also measured. The use of GPS leads to readily obtained and useful engineering data for continued monitoring of structures.

Elastic buckling of perforated plates subjected to concentrated loads

Abstract Results are presented for concentrated loading applied to perforated plates of different aspect ratios. Two different in-plane restraint conditions and four edge conditions have been analysed. The results have been obtained by the application of the conjugate load/displacement method of elastic stability analysis, and show how simple modifications to plate geometry, particularly with respect to perforation aspect ratio and support conditions, can effect major changes to the elastic critical load.