Development of membranar effects in frame beams: experimental and analytical investigations

Recent events such as natural catastrophes or terrorism attacks have highlighted the necessity to ensure the structural integrity of buildings under exceptional events. According to Eurocodes and some different other national design codes, the structural integrity of civil engineering structures should be ensured through appropriate measures but, in most of the cases, no precise practical guidelines on how to achieve this goal are provided. A European RFCS project called “Robust structures by joint ductility” has been set up in 2004, for three years, with the aim to provide requirements and practical guidelines allowing to ensure the structural integrity of steel and composite structures under exceptional event through an appropriate robustness.
The investigations performed at Liège University, as part of this European project, are mainly dedicated to the exceptional event “Loss of a column in a steel or steel-concrete composite building frame”; the main objective is to develop a simplified analytical procedure to predict the frame response further to a column loss. The development of this simplified procedure is detailed in two complementary PhD theses: the thesis of J.-F. Demonceau and the thesis of H.N.N. Luu. The present paper describes experimental and analytical studies carried out within the first PhD thesis. In particular, a simplified analytical method allowing the prediction of the frame response with account of the membranar effects is described.