Static and dynamic analysis of a reinforced concrete flat slab frame building for progressive collapse

The problem of structural progressive collapse has been investigated using a real-scale reinforced concrete flat-slab frame building, which has survived collapse after two of its central columns had been physically destroyed. The numerical study undertaken considers three loading scenarios, in which alternately three different columns are being instantaneously removed, and in each case the structural response of the frame is calculated. A finite-element linear static analysis has first been conducted. To account for severe dynamic effects occurring during fast dynamic events, such as explosions or impacts, dynamic linear and nonlinear time history analyses have next been performed. For each scenario the results have been processed in terms of demand-resistance ratios at critical cross-sections, and thus it has been assessed whether the building would be susceptible to progressive collapse according to certain allowance criteria prescribed in technical guidelines. In this respect, three definitions of dynamic factors are introduced and their effective applicability is assessed in view of actually calculated and guidelines-suggested values. Results show overall that the approaches of linear static and dynamic analyses would have produced progressive collapse conditions. The nonlinear dynamic analysis predicts no mechanism which might lead to progressive collapse, even though several plastic hinges would be formed. Merits of using static or dynamic, linear or nonlinear analyses are discussed.