Seismic performance evaluation of reinforced concrete shear wall seismic force resisting systems

Building codes in various jurisdictions including Canada are moving towards performance-based design approaches where a structure is designed not only to have adequate strength, but also for the required performance attributes, such as, adequate deformability. From that point of view, performance assessment of structures in the design phase plays an important role in the implementation of the above concept. The focus of this article is to study the seismic performance and torsional sensitivity of reinforced concrete shear wall buildings designed using the seismic provisions of the National Building Code of Canada (NBCC 2005) and the Canadian standard on reinforced concrete buildings (CSA-A23.3-04). The buildings considered here are of regular plan and the height is limited to what is permitted for the use of the Equivalent Static Load (ESL) method of the building code. A set of three reinforced concrete buildings of four, eight and sixteen storey heights are designed here. The buildings are assumed to be located in Vancouver and various levels of accidental mass eccentricity up to 10% as permitted in the ESL method, are considered. After the preliminary design of the buildings using the ESL method, dynamic elastic Response Spectrum Analysis "RSA" has been performed to compare the base shear and make appropriate refinement in the design as suggested in NBCC. The buildings are then analyzed using inelastic dynamic analysis with fifteen recorded accelerograms of past earthquakes. The earthquake records are selected such that the peak velocity to acceleration ratio of each record is compatible to the seismicity of Vancouver. The ground motion records are scaled to fit the design spectrum using two different methods, The performance parameters such as the demand to capacity ratios for storey drift, plastic rotation, and storey shear are extracted from the results of the inelastic dynamic analysis. The statistical quantities such as mean, standard deviation and the maximum values of the demand to capacity ratios are found to be well below the acceptable limits, while the storey shear, exceed the limit in all cases. It also is observed that none of the buildings are torsionally sensitive within the code specified range of eccentricity for which ESL method is applicable. The changes in the dynamic response due to the change in eccentricity are almost proportional within the range of eccentricity considered here. Another point to note here is that while results for the four and eight storey buildings are not very sensitive to the method of scaling of the ground motion records, for the sixteen storey building, it is not so