The inelastic seismic responses of plan asymmetric multi-storey reinforced concrete moment-resisting frames stiffened with ductile reinforced concrete structural walls have been investigated under bi-directional far-field and near-field ground motions. Asymmetric models were created by adding shear walls in two orthogonal directions of some symmetric frames developed using the generic structures algorithm. A realistic modelling of the non-linear ductile behaviour of reinforced concrete elements was utilised in combination with both mass and stiffness eccentricities in dynamic torsional response of asymmetric buildings. The torsional responses of models including the ductility demands for both stiff and flexible edge elements including shear walls and columns were normalised to the corresponding values of the symmetric models. The distribution of normalised ductility demands along the height of structures was used to assess the torsional effects in multi-storey structures. It was also shown that for dual lateral load-resistant systems, columns at the corners of flexible sides demand more ductility compared with similar frame systems.
Most of studies that examined the influence of incidence angles of bidirection ground excitations were focused on the estimation of engineering demand parameters (EDPs) only along two orthogonal axes varying ground motion orientations. However, variations of the EDPs have not been assessed in a desired horizontal angular distance from a reference direction that could be different than the incident angle. Furthermore, the structural demands along the height of structures were not also studied for different angles of the incident of ground motion. The current paper aims to assess these issues introducing spatial distribution of ductility demands and damage index induced to multi-storey reinforced concrete frames due to incidence-dependent bidirection ground excitations. Employing the concept of 3D archetypical frames, several pushover analyses and nonlinear response history analyses were conducted using two sets of ground motions classified as nearfield and far-field records. The results of these comprehensive parametric analyses including the EDPs along different angular distances from a reference point were employed to perform regression analyses obtaining the critical EDPs. Several expressions for the critical EDPs (mostly oriented in non-principal planar directions) are suggested in terms of the orthogonal peak responses assumed to be assessed corresponding to the principal axes. Different expressions proposed in this study could be used to predict the critical ductility of structures by combining the structural ductility in two perpendicular directions when they are assessed due to the principal directions of excitations.
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