The purpose of this paper is to record our approach to the design of glass structures and to provide a discussion forum for engineers who are interested in the subject. Over the last 20 years architects have been interested in the potential of glass as a primary structural element and as members of the design team structural engineers have been encouraged to take responsibility for ensuring that the solutions proposed are safe and practical. Currently national standards are available in draft form and it is anticipated that these standards will become available in the near future. However until the standards have been published structural engineers will need to rely on assessing the information that is available in various texts and trade literature and on their own experience. In this article we will outline the history of our approach to the design of trafficable glass surfaces, stair treads and floor plates, and in the process share the information we have gathered and the ideas that we have developed which although lacking the comfort of a codified approach have in general resulted in practical and safe solutions. Tim Macfarlane, BSc, CEng, HonFRIBA, FRSA, MIStructE, FConsE Dewhurst Macfarlane and Partners
The existing methods of ground slab analysis either provide designs which are too conservative or have other inadequacies. The two main inadequacies are that frequently they do not show good agreement with test results and they do not provide a rational basis for determining the radius of circumferential cracking around a localised load. It is suggested that the reason for these shortcomings is the absence of membrane action consideration in those methods. Membrane action needs restraint from surroundings which small slabs do not provide and therefore has not warranted much attention. It is only now worthwhile considering membrane action owing to the growing use of large area, jointfree, slab construction processes. Recent research is described in this paper showing the effect of the stiffness and the strength of the slab areas surrounding a mechanism resulting from a local overload on a ground slab. Research which was intended to identify rationally the value of the self-selecting radius of a rigid-plastic yielding mechanism revealed that a migrating system operates with a moving hinge shifting the mechanism radius during failure. The result, which needs further experimental work and adaptation for design use, promises to provide more economic designs through its consideration of membrane action and also a more faithful analysis of the mechanics. John Eyre, BA, BSc, PhD, RIBA Department of Civil & Environmental Engineering, UCL
Wembley Arena forms a key part of a massive regeneration of the area surrounding the new Wembley Stadium. This paper gives a brief history of the former Empire Pool, a state of the art reinforced concrete structure when built in 1934, explains its context in relation to the new Wembley Stadium development, and describes how many structural challenges were overcome to enable the major redevelopment of an important listed building. Cliff Buckton, MSc, DIC, CEng, FIStructE, MICE Regional director, property, Halcrow Yolles Kevin Reeder, BEng, CEng, MIStructE Principal engineer, building structures, Halcrow Yolles