Shear force magnification in reinforced concrete walls of high-rise buildings designed according to Eurocode 8

The paper contains a discussion of shear force magnification in reinforced concrete (RC) walls of high-rise buildings designed according to Eurocode 8. An extensive study is performed in order to examine the applicability of Eurocode 8 procedure in determination of shear forces in RC walls of high-rise buildings. In addition, the applicability of Eurocode 8 provisions related to ductility classes for seismic design of RC high-rise buildings is investigated. 20-storey, 30-storey and 40-storey RC high-rise buildings with core wall structural system are selected as prototype buildings in presented study. 180 nonlinear time-history analyses are conducted for 60 ground motion records with a wide range of magnitudes, distances to source and various soil types including in this way uncertainties of ground motion selection. Nonlinear 3D models of the prototype buildings are constructed. Shear force magnification factors obtained by Eurocode 8 procedure are compared with the results of nonlinear time-history analyses. The current formulation of Eurocode 8 procedure yields significantly incorrect results when it is applied to RC walls of high-rise buildings. The conducted analysis has clearly indicated the possible modifications and improvements in calculation of the Eurocode 8 magnification factor epsilon for RC walls of the high-rise buildings. The need of introducing a single ductility class for RC walls of high-rise buildings is pointed out. The corrected magnification factor epsilon(cor) defined in a more general way with variable ratio of second mode shear force to the first mode shear force at the base of the wall is proposed. Further, based on the corrected magnification factor epsilon(cor) the shear force design envelopes for RC walls of high-rise buildings that best match the actual shear forces obtained from nonlinear time-history analysis are proposed.