| The coupling beams of R. C. shear walls often suffer severe damage in previous intense earthquakes, so it’s important to find a new style of coupling beam with better seismic performance. As under lateral load, the shear force of coupling beams is uniform distributed, and the minimal moment is at the middle of the span, so we can cut the beam at the middle into two equal parts, connect them with shear damper. In this way, the shear deformation and earthquake energy of the coupling beam can be mostly occupied by the damper, and the concrete parts of the beam and the wall panels can be saved.This paper firstly introduces the common earthquake damage of R. C. coupled shear wall and the necessity and means to ameliorate; introduces existing types of energy dissipation coupling beams, explains the meaning and purpose of proposing a new type; introduces the theory, type and mechanic models of common passive energy dissipation dampers, and selects the metal dampers as the analyze object based on the purpose of this type of dampers.Secondly, this paper summarizes the shear wall requirements to the dampers, analyzes and derives the requirements by qualitative and quantitative methods, proposes the design measures and parameterized expressions, demonstrates the main idea to analyze this type of structural member, and provides suggestions for design and application. One important requirement is to ensure the stiffness of the shear wall after equipping the dampers, so to discuss the effect of the dampers to the shear wall stiffness, the relationship between coupling beam stiffness ratio and shear wall stiffness ratio is analyzed, the main factors to the relationship and their trends are interpreted, and the suggested span of coupling beam stiffness ratio in engineering design is proposed. Based on the parameterized expressions mentioned above, the design flow objected to bilinear model parameters of the metal dampers is demonstrated, and an design example of a1:1rectangle-section mild steel shear damper is explained in detail.Thirdly, several practicable elastoplasticity simulation methods of shear wall with energy dissipation coupling beams are proposed, which based on ABAQUS, SAP2000, and Seismostruct platform, and by the combinations of layered shell element, LINK element, common shell element and fiber element, the contradiction between analysis efficiency and the need of detailed modeling of energy dissipation coupling beams can be effectively solved. The accuracy of these methods are validated by comparison among test results and different method simulation results, the merits, drawbacks and applicable situations are discussed and explained, and the method being used in this paper is selected according to the features of the study subject.Fourthly, two coupled shear walls are selected as the original structure, based on which the shear dampers on bisected coupling beams are designed through the design flow proposed above, and by the simulation method selected, static pushover analysis and quasi-static cyclic analysis of the shear walls before and after equipping dampers are carried out. The simulation results show that after equipping the dampers, the ductility of the structure increases obviously, the stiffness and load capacities have not been reduced too much, the dampers yield before coupling beams and wall panels, structural deformation modes stay the same, hysteretic loops of the structure become fuller, the energy dissipated by the dampers holds40%of the energy absorbed by the whole structure, and the additional damping ratio of the dampers reaches5%. One thing should be aware of is when using the design method proposed in this paper, the original structure should be in the condition that the coupling beams yield before the wall panels, because from the simulation results, the effect of equipping the dampers is much more obvious for structures whose coupling beams yield before the wall panels. In general, the results show that shear walls with dampers perform better in seismic loads, and the purpose of equipping the dampers has been reached.Last, the time-history elastoplastic analysis of a typical R. C. frame-shear wall building with and without shear dampers are carried out by simulation method introduced in this paper. The results show that the dampers designed through the design method proposed in this paper can maintain the original stiffness of the shear wall, at the same time reduce the earthquake energy absorption of the whole structure, as well as improve the distribution of the plastic hinges and energy dissipation mode of the structure. Through the simulation analysis of two shear walls and a frame-shear wall building, the design method in this paper is validated, which provides a new idea of the study and application of the repairable coupled shear wall system. |
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