Study On Seismic Design Methodology For Frame-shear Wall Structures With Mild Steel Damping Walls In Highly Seismic Region

With the continuous improvement of people's awareness to earthquake disasters as well as the development of science and economy, passive energy dissipation devices are widely used. The combination forms of structures and passive energy dissipation devices are varied. Among those forms, the combination of frame-shear wall structures and mild steel damper which features excellent performance, low cost and easy construction as one of the passive energy dissipation devices, has received extensive attention against the background that frame-shear wall structures have gradually become the mainstream of high-rise building, and this form has already been applied in actual project. However, the seismic performance of this new structure system has not been fully investigated. Moreover, the research objects are mostly reinforced concrete or steel frame structures among all the current earthquake-reduction design methods which are basically based on a single performance objective. Thereby, studying on the seismic performance and new design method which aims to achieve multi-level fortification objects for frame-shear wall structures with mild steel damping walls are the key to promote practical application.In this paper, frame-shear wall is taken as the research target. Based on the analysis of mild steel damping wall presented in this paper and the seismic performance of frame-shear wall structures with mild steel damping walls, a performance-based seismic design method is put forward. The main research and results are provided as follows:(1) The types and hysteretic models of the mild steel dampers here and abroad as well as the earthquake-reduction design methods are comprehensively reviewed. Some problems existing in the practical application of mild steel dampers were pointed out.(2) Based on the deficiency of mild steel dampers in the practical application, a new type of mild steel damping wall with diamond-shaped hole is presented. It is arranged along the full height of the floor. The specific configuration and connection type are shown in this paper. Based on the mechanism of energy dissipation, the formulas of elastic stiffness, yield force and yield displacement for this mild steel damping wall are established. The refined finite element models of this new mild steel damping wall are developed within environment of ANSYS. And considering the effects of shear span aspect ratio of tapered beam ?=l/bbe,width-to-thickness ration of tapered beam ?= bbe/t, ratio of total link length in the vertical direction to the wall height ?= ml/h, swing radius of the stiffenerr and the direction of displacement loading on the mechanical property of this mild steel damping wall while the peripheral dimensions is constant. The results show that the proposed mild steel damping wall has clear mechanism of energy dissipation, uniform stress distribution and relatively high elastic stiffness as well as yield force. It exhibits full hysteretic curve and Bouc-Wen model can be selected as the mechanical model. Besides, Simple and reliable connection, high utilization of materials along with the convenient replacement will lead to a high practicality of the new mild steel damping wall.(3) Based on the cooperative working theory of frame-shear wall structures in elastic and elastic-plastic situations, the effect on seismic performance by adding mild steel damping wall is considered. It can be learned that adding mild steel damping wall can effectively control the displacement. The equivalent additional stiffness will change the lateral displacement model and the distribution of internal forces of frame-shear wall structures. The equivalent additional damping will have better control effectiveness of stiffness degradation and can decrease the damage of shear wall. The percentage of shear forces assumed by the frame reduces and the frame achieves greater security.(4) A new design method which aims to achieve multi-level fortification objects for frame-shear wall structures with mild steel damping walls is presented and applied to a practical engineering. The effect on cooperative working performance of frame-shear wall structures by adding mild steel damping wall is considered in this method. Moreover, it has the virtue of clear parameter design method and proved to be feasible and practical.