Application of a recently proposed displacement-based assessment procedure for asymmetric-plan RC wall buildings

Architectural layouts of reinforced concrete buildings often require structural walls, with varying dimensions, to be placed in an asymmetric plan configuration. During seismic excitation the asymmetry induces a torsional component of response, which can impact negatively on the performance of the building by increasing demands on both structural and non-structural elements. Furthermore, the torsional response can render existing assessment procedures less effective at providing an accurate estimate of engineering demand parameters. In this paper a recently proposed displacement-based assessment procedure, developed specifically for asymmetric-plan RC wall buildings, is applied to a case study structure. The method is based on a combination of two existing approaches, with the first being used to predict displacement demands in symmetric reinforced concrete wall buildings, and the second being used to account for torsional response in 2D asymmetric-plan systems. One of the key aspects of the procedure is the concept of assigning effective stiffness properties to the walls. In doing so the method is able to account for the influence of not only stiffness eccentricities but also strength eccentricities, which have been shown to play the more important role during inelastic response. Higher-mode effects, which can have a strong influence on a number of engineering demand parameters, are accounted for using existing simplified expressions. The case study structure under consideration is an eight storey RC wall building designed in accordance with Eurocode 8. It is modelled using a lumped plasticity approach and then assessed using nonlinear response-history analysis over a range of increasing intensity levels to establish benchmark estimates of several relevant engineering demand parameters. The new displacement-based assessment procedure is then used to assess the building in an equivalent incremental framework. The analyses are then repeated with Modal Pushover Analysis to provide another point of reference for evaluating the new approach. Comparison of the results shows that the newly proposed procedure performs to a satisfactory level in predicting displacement demands and wall shear forces in the case study building. Discussion is given on the relative merits and drawbacks of the new approach. One of the most significant advantages is that it can deal with what is arguably a highly complex analysis problem without the need of a numerical model. Its major disadvantages are that it is iterative and in its current form cannot account for bidirectional eccentricities of bidirectional excitation. However, it is deemed that the good results obtained in reference to the case study building and its appealing theoretical basis warrant its further development.