Tuesday 24th June 2014, 6.00pm for 6.30pm start
‘Fail safe or fail dangerous?’, Dr Ahmer Wadee (Imperial)
Abstract
Structural engineering has a rich history with its landmark monuments and numerous personalities. As a discipline, it relies fundamentally on nonlinear mathematics, which can reveal whether structures are vulnerable to catastrophically dangerous collapse (or failures) or those that can be contained. Structural failure is inherently a nonlinear process with the nonlinearities grouped into two broad categories: material and geometric. Material nonlinearities arise either intrinsically from the material response (e.g. concrete, aluminium or timber) or when materials that obey Hooke’s law (e.g. steel) are overstressed and permanent damage or fracture occurs and sudden changes in material behaviour are observed.
We will focus our attention to geometric nonlinearities, which are generated in structures experiencing large deflections. These may rapidly occur when the phenomenon known as buckling, when structures change from stable to unstable equilibrium, is triggered. Buckling is most likely in components that are made from slender elements that are wholly in, or in-part, compression such as columns and beams. After buckling is triggered a small change in load may lead to disproportionately large deformations and structural collapse. We shall see that nonlinear mathematics provides key tools that allows engineers to assess robustness and make informed decisions about whether potential failure modes are catastrophic or otherwise. Recent developments regarding the process known as “cellular buckling” will also be outlined; under certain circumstances, imaginative use of that buckling process can even be exploited to enhance safety.
Venue: Room 201 Skempton Building, Imperial College, London (closest tube – South Kensington). Building no. 27 on Imperial College map