Abstract
The effect of mega braces on structural stiffness has been comprehensively discussed for various megabraced frame-core tube structures. However, few studies have considered how mega braces affect the failure mechanism of mega structures exposed to seismic action, which is a nonlinear process. To address this issue, we present a study on the effects of different brace patterns on the failure mechanism and seismic performance of megabraced frame-core tube structures. Specifically, the yield order of components, the distribution of plasticity, the distribution of internal forces, the degradation of structural nonlinear stiffness, and the behavior factor have been investigated. This study reveals that the yield of mega braces will change the deformation mode of adjacent mega columns and thus affect the plasticity distribution of adjacent substructures. The enhancement of mega braces improves the exterior tubes (thereby increasing their capacity to serve as the second line of seismic defence), mitigates the rate at which system stiffness degrades, and improves the overstrength of the structural systems. In addition, after the yield of mega braces, the maintenance of a higher-amplitude axial force changes the proportion of internal force components in mega columns, reducing their ductility and further affecting the overall ductility of the structural system.
Highlights
Most studies of the seismic performance of megabraced frame-core tube structures focus on mechanical characteristics, structural deformation characteristics [13], and the verification of the performance-control parameters under design seismic conditions [2, 14]
Some research has considered the differences in the energy dissipation distribution and the collapse capacity under the design seismic condition with various braced schemes [1, 15]. ese studies concluded that the chosen brace pattern affects the distribution of structural internal force and even changes the nonlinear development process of the structures
Is section analyzes the nonlinear incremental dynamics [37] by applying the three normalized earthquake records shown in Figure 24: the El Centro earthquake (NS), the Imperial Valley earthquake, and arti cial ground acceleration. e response spectrum values of arti cial ground acceleration are matched with Chinese seismic codes
Summary
We designed three prototype 50-story 4 × 4-bay megabraced frame-core tube structures in accordance with the current Chinese Code for Seismic Design of Buildings [18] and the design of Tianjin 117 Tower [19]. e current Chinese Code design method classifies structural components according to the importance of components. Taking 5MBC as the main analysis model, another 15 structural models were obtained by adjusting the parameters of the main components (e.g., the thickness of the shear walls, the height of coupling beams, the height of the primary-frame beams, the height of the primary-frame columns, and cross-sectional area of braces). E letters C, LL, ZL, Z, and B represent the thickness of the shear walls, the height of the coupling beams, the height of the primary-frame beams, the height of the primary-frame columns, and cross-sectional area of the braces, respectively. E load distribution based on the first mode was used in nonlinear static pushover analysis In this model, Q345 steel with the yield stress of 345 MPa was chosen for the tube of the primary columns and the braces, and HRB400 rebar with the yield stress of 400 MPa was used for the concrete members. The strength loss of each section can be considered in the nonlinear deformation process by the strength loss of the ber material and the strength loss of the plastic hinge
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