When a super-tall building is designed, a member-to-member model is constructed to represent the assembly of columns, beams, walls and so on. The seismic response analysis using this model is computationally expensive and outputs large amount of data. Therefore, an equivalent mass-spring system with a small number of elements and short analysis time is useful at the initial design stage. Since the influence of bending deformation becomes large as building becomes taller, it must be simulated by the equivalent mass-spring system. The companion paper (Part 1) therefore proposed a simplified method to formulate such an equivalent system, and named it as the bending-shear model. In this paper, we extend the modeling method to and verify the model accuracy for various super-tall buildings.
We consider four different buildings heights from 80m to 400m, as well as three different structural frames such as moment resisting frame, center core frame, and outrigger frame combined with center core. The method can be easily applied to these various frame types because the bending stiffness is calculated using only horizontal displacement given as the overall responses, in contrast to existing method that considers deformations of all the vertical members. Note however that the pure moment loading analysis discussed in the companion paper is modified to cover different systems mentioned above, considering their distinct distributions of column axial deformations.
The bending stiffness of bending-shear model obtained with the pure bending moment analysis is larger than member-to-member model appear to under story moment and shear forces. Therefore, the proposed method corrects the bending stiffness of bending-shear model. Correction coefficient is designed to the second natural period of bending-shear model match member-to-member-model. As such, the second eigenvector and third natural period and eigenvector match fairly well regardless of the structural frame type. Moreover, the building responses can be easily separated into bending and shear components by using the bending stiffness and shear stiffness obtained the proposed method. This is the first method that can clearly evaluate the contribution of each shear and bending components to each mode.
