Efficient modelling of RC walls for accurate simulations under earthquake loading
Creators: name: Xie, Haochen
Publisher: name: Imperial College London
Year: 2022

description: Remarkable advances have been achieved in earthquake engineering in the past decades, given the growing awareness and concern regarding the global seismic risk. In the wake of the damage wrought by the recent earthquakes, reinforced concrete (RC) walls are commonly employed as effective seismic resisting components in new building structures or retrofitting solutions to enhance the seismic performance of existing sub-standard frame buildings. Current codes of practice recommend using nonlinear dynamic analysis as the most accurate technique for the seismic evaluation of RC buildings under earthquake loading. This necessitates the development of reliable numerical strategies for accurate simulation of RC walls under cyclic loading conditions representing seismic actions. This research starts with a critical appraisal of currently available modelling strategies for RC walls associated with different levels of sophistication. They include: (i) the wide column approach with 1D beam elements, (ii) 2D FE models with nonlinear shell elements and (iii) detailed 3D FE descriptions with solid elements and embedded bar elements. Numerical simulations have been performed considering experimental slender and short wall specimens subjected to cyclic loading. Numerical-experimental comparisons highlight some drawbacks of existing modelling strategies as their inability to represent the actual degradation of strength and stiffness and the pinching characteristics of the cyclic behaviour, especially in the case of wall samples whose response is governed by flexure-shear interaction. In view of these limitations and to achieve more accurate response predictions, an efficient and practical 2D macro-element representation for RC walls is proposed in the second part of the research. It incorporates a biaxial concrete model based on the rotating crack approach to account for the nonlinear response under cyclic loading conditions. Accuracy and efficiency of the macro-element model have been demonstrated by validation studies, focusing on RC walls with different aspect ratios and an RC coupled wall system. The ability of the proposed model to predict the main cyclic response characteristics of RC walls, including stiffness and strength degradation, energy dissipation capacity, and pinched shapes of the hysteresis loops, has been confirmed by a favourable agreement between the numerical predictions and experimental findings. The final part of this research proceeds with an application study on seismic analysis of a realistic four-storey RC frame-wall building. The developed macro-element model accounting for shear deformability and potential shear damage and failure provides a more realistic representation for RC walls than the wide column approach widely used in practice. Moreover, the macro-element modelling strategy requires a comparable computational cost to the wide column approach, which renders it suitable for nonlinear dynamic analysis of large scale structures and realistic seismic assessment of RC buildings with shear walls.