A new design method is proposed for the structural, load bearing applications of glass with ground edges. It is shown that all the strength characteristics of glass relevant to structural engineering can be explained by the cracks present in the glass and can be analysed using fracture mechanics. The proposed method takes a ‘design crack’ as the basis for design, rather than an allowable stress, as in current approaches with which it is compared. This paper deals with the determination of the strength of glass elements; it does not address buckling problems, nor does it consider the concepts of alternative load paths. The role of crack size design within the wider philosophy of limit state design is discussed. M. I. Porter, BE (Hons) Department of Engineering Science, University of Oxford Professor G. T. Houlsby, MA, PhD, FREng, FICE Department of Engineering Science, University of Oxford
This paper reports on work carried out to develop a structural composite using homegrown timber. The overall objective of the work was to improve the structural performance of timber beams by laminating and incorporating fibre reinforcement, with the intention of substituting native timber for imported timber. The first part of the programme involved both theoretical analysis and laboratory-based experimental work, in order to identify suitable reinforcing materials and compatible adhesives. It was established that the most effective reinforcement was a pultruded unidirectional carbon fibre-reinforced polymer (CFRP) strip. The next part of the programme concentrated on the fabrication and testing of composite beams. This progressed from small-span beams to 3m-span laminated beams and then to 6m-long laminated beams fabricated in commercial workshop conditions. The investigation of the theoretical and experimental behaviour of these 6m beams is the main focus of this paper. For modest reinforcement ratios a considerable increase in both bending stiffness and ultimate load capacity has been achieved. In addition, the behaviour at ultimate load has been found to depend on the compressive behaviour of the timber and shows much improved consistency compared with the inherent variability of the non-reinforced Sitka spruce beams. J. R. Gilfillan, BSc(Eng), PhD The Queen’s University of Belfast S. G. Gilbert, BSc(Eng), PhD, CEng, MIStructE, MICE The Queen’s University of Belfast D. P. Russell, BEng, PhD Kirk McClure Morton (formerly The Queen’s University of Belfast)