Effect of Design Ductility on the Progressive Collapse Potential of RC Frame Structures Designed to Eurocode 8

Abstract

Abstract:Progressive collapse is the cause of most structural failures around the world. The US General Service Administration (GSA) has presented guidelines for the assessment of the vulnerability of building structures to progressive collapse. It has been established in literature that the philosophy of ductility and redundancy used in seismic design is beneficial in resisting progressive collapse but not accounted for in these guidelines. The GSA methodology is particularly suited to seismic codes which allows for a constant member rotation but may be unsuitable to other codes that makes provision for ductility level. In this study, an investigation into the progressive collapse potential of RC framed structures designed to the seismic design code, EC 8, with varying design ground accelerations and ductility classes under different column loss scenarios was done. Based on the EC 8, a criteria for maximum plastic rotations and dynamic multiplies for progressive collapse analysis was proposed. These proposed criteria, together with the GSA criteria, were used to investigate the designed structures. The EC 8 criteria proved that buildings designed for higher ductilities yield at lower loads but undergo greater deformations and absorbs more energy to resist collapse. On the other hand, buildings designed for lower ductilities have higher yield loads but undergo lower deformations before collapse. Higher PGAs result in higher yield strengths but does not necessarily deformation capacity. This effect of ductility was not seen with the GSA criteria since a constant rotation capacity was recommended for all the buildings regardless of design ductility. It was also found that the removals of a corner column possess the greatest threat to progressive collapse on a building.

An evaluation of the GSA Nonlinear Static Progressive Collapse Methodology applied to EC 8 Seismically Designed RC Moment Frames

“…By comparing maximum load factors, it was observed that the resistance of the structure to collapse is lowest when a corner column is lost (Case 3) since it has the lowest load factors and ductilities. The conclusion of the corner column loss case being the most critical is consistent with the findings of [17], [18] and [19] who all showed that reinforced concrete buildings were most vulnerable to progressive collapse when a corner column is lost. 25 is the only model found vulnerable to progressive collapse in all these cases because the GSA methodology prescribes a maximum load factor of 2.0 to assure resilience to progressive collapse.…”

Fragility and robustness analysis of a multistorey RC building

“…A certain similarity can be observed between numerical procedures for the analysis of progressive collapse, and the analysis of structures exposed to earthquake action. The influence of the structure's ductility on progressive collapse of the system is investigated in [87], because [15] excludes ductility and residual bearing capacities, which is used in seismic design. The corresponding regulations can be used to reduce the likelihood of PC.…”