Numerical Study Of Composite Shear Wall With Confining FRP Tube Embedded CSFT Edge Columns

In tall or super-tall buildings, reinforced concrete shear wall or reinforced concrete core tube is the main lateral force-resisting system of the structure system. However, these structural elements are prone to cracking under the attack of a strong earthquake and/or the vertical loads, leading to a large deformation. Against this background, this thesis presented a numerical investigation into a new type of composite shear wall, namely composite shear wall with confining FRP embedded CFST columns developed from the shear wall with confining CFST columns. A series of parametric studies were carried out to show the effects of a number of significant factors, such as axial compression ratio、confinement stiffness of FRP, the strength of concrete,steel ratio and aspect ratio, on the behavior and seismic performance of the new type of composite shear wall. The advantages of the new shear wall were demonstrated by the numerical results. The main contents covered by this paper includes the following parts:1)An FE model was first established in ABAQUS for the shear wall with confining CFST columns. The FE model was substantiated and improved using experimental results(load-displacement curves and failure mode) from existing literature.2) A parametric study was carried out using the above ABAQUS model to compare the performance of composite shear wall with confining FRP tube embedded CFST columns(SW-1), shear wall with double-skin CFST edge columns(SW-2), and normal shear wall with CFST edge columns(SW-3). The numerical results show that the load-carrying capacity of SW-1 is increased by 13.7% and 20.2% compared to those of SW-2 and SW-3 respectively, while its coefficient of ductility is increased by 16.5% and 19.2% respectively and its index of energy dissipation by 13.5% and 20.5%. Similar to SW-2 and SW-3, the SW-1 has secondary stiffness in its load-displacement curves. As a result, it can be said that the SW-1 has better overall structural performance compared to the other two types of shear walls(i.e. SW-1 and SW-2).3) Parametric study was also carried out using the above FE model to explore the structural performance of SW-1 subjected to both axial loading and moment, aiming to investigate the effects of different factors on the structural performance of SW-1. The numerical results show that with the increase of axial compression ratio(axial load divided by axial load-carrying capacity), both the load-carrying capacity and ductility of SW-1 are decreased; with the increase of concrete strength, the load-carrying capacity, ultimate displacement and initial stiffness of SW-1 are increased, while the ductility is decreased. With the increase of either steel percentage ratio or the confinement stiffness of FRP of edge columns in SW-1, load-capacity, ultimate displacement, initial stiffness as well as the ductility of the wall are increased with the confinement stiffness of FRP having more significant effect on the above structural indexes. When the high-to-width ratio of the shear wall section is increased, the failure mode of the shear wall may change; as a result, all the structural indexes are declined.4) The last parametric study carried out using the above FE model to explore the energy dissipation performance of SW-1 under cyclic loading. The numerical results show that the fullness as well the area surrounded by the hysteretic curve of the load-displacement response is decreased with the increasing the load ratio, but increased with the increase of confinement stiffness of FRP. With the increase of both axial compression ratio and the FRP confinement stiffness, the degradation of post-yielding stiffness of the shear wall can be allayed. As a result, it can be said that the energy dissipation performance is significantly affected by the axial compression ratio; the increase of confinement stiffness of FRP increases the energy dissipation of the new shear wall, and postpones the degradation of post-yielding stiffness of the shear wall.