Robustness assessment using nonlinear analysis methods: a parametric study

In the study presented in this paper, static and dynamic nonlinear analyses were undertaken on representative planar frames with a range of different geometrical and mechanical parameters, with the aim of assessing whether analysis methods drawn from current seismic design principles can be successfully applied to the case of a typical robustness scenario, where a column is suddenly lost as a result of an accidental action. It was shown that static nonlinear methods of analysis can provide a good approximation of the structural response. Seismic detailing was found to significantly improve robustness, with higher benefits seen at low ductility levels, and similar trends to what is currently known within earthquake engineering were obtained. The geometric nonlinearity was found to be critical, allowing for a realistic representation of the structural performance. Increasing the number of storeys was shown to enhance progressive collapse resistance, while gravity loads tend to increase progressive collapse and ductility demands; on the contrary, equivalent viscous damping was shown to reduce the ductility demand. Removal time was found to be of primary importance on the structural response, with inertial effects significantly being reduced when the removal time is longer.