Abstract
Application of a fibre-element nonlinear modelling technique for seismic collapse capacity assessment of RC frame buildings in comparison with conventional lumped plasticity models is investigated in this paper. Constitutive material models of concrete and steel for fibre elements are adopted to enable simulation of the loss in vertical load carrying capacity of structural columns. Inclusion of the nonlinear second order P−Δ effects accelerated by degrading behaviour of steel and concrete materials in the fibre model allows prediction of the sidesway mode of collapse. The model is compared with nonlinear lumped plasticity models in which stiffness and strength degradation is replicated through degrading parameters in structural components. Static cyclic analyses of an example cantilever column and a portal frame indicate that the variation of axial loads in columns may result in accelerated degradation and failure of structural components which is not taken into account by lumped plasticity models. Moreover, incremental dynamic analysis of a ten-storey RC frame shows that the lumped plasticity model may overestimate building collapse capacity when vertical failure of structural components occurs prior to sidesway instability.
Highlights
As collapse of buildings is the primary source of casualties in earthquakes, protection against collapse has been explicitly stated as an important objective of seismic design codes for many years
Application of a fibre element model to predict the seismic collapse of RC buildings was proposed in this paper
Through analysis of a case study 10-storey RC frame building designed according to New Zealand standards, it was shown that the fibre element model enables simulation of structural failure due to the loss in vertical load carrying capacity of the columns
Summary
As collapse of buildings is the primary source of casualties in earthquakes, protection against collapse has been explicitly stated as an important objective of seismic design codes for many years. In response to the need for methods to quantify collapse potential of buildings, several studies in the last decade have been devoted to collapse potential prediction of buildings [2,3,4,5,6,7]. These studies have generally been focused on three aspects of collapse assessment: (i) structural modelling, (ii) selection of ground motions for collapse assessment and (iii) uncertainty estimations. While the significance of each aspect of the collapse assessment is acknowledged, this paper concentrates on the improvement of the structural modelling for prediction of the collapse probability of buildings
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