# Optimization Design of Coupling Beam Metal Damper in Shear Wall Structures
## 1 Introduction  
Based on the assumptions of ductility design, coupled shear wall structures should satisfy the features of a \"strong wall with a weak coupling beam\". Such a setup will guarantee that a structure has enough stiffness to allow the shear wall to not fail first during rare earthquake events. In these scenarios, a plastic hinge would dissipate the energy and ensure that the shear wall will not yield too early. The ductility of coupling beams is one of the most important factors that influence the ultimate bearing capacity, and both shear force and deformation requirements should be met by a coupling beam under reciprocating load which occurs in earthquakes. A great deal of research has been done around the globe to explore approaches to satisfy the ductility requirements of shear wall beam structures.  
[PERSON] et al. [1] improved the behavior of commonly-used reinforcement concrete using diagonal crossing reinforcement, which can remarkably improve anti-seismic features. [PERSON] [2] proposed placing stiff coupling beams on the top of a shear wall structure in order to strengthen the structure's integrity and to improve lateral stiffness. [PERSON] and [PERSON] et al. [3; 4] raised the idea of metallic dampers, which, made out of metal, could have the advantage of the material's plastic yield feature to dissipate earthquake energy inputs. [PERSON] et al. [5; 6; 7] developed the concept of a changeable steelcoupling beam, which features a weakened middle part (namely the safety wire) that can dissipate energy via shear yielding and is easy to switch after damage. [PERSON] et al. [8] used bending as a damper energy dissipative form and set up a frictional damping device in the middle of a coupling beam that can decrease the response of the shear wall structure during earthquakes. [PERSON] et al. [9; 10] developed a compound energy-dissipation damper, in which high-damping rubber material and two U-shaped steel plates were combined to acquire high energy dissipation. [PERSON] [11] developed a new type of visco-elasticity damper which could potentially replace the coupling beam damper. [PERSON] et al. [12] proposed a new shape for memory alloy dampers that restore their original shape after damage, and do not require replacement as coupling beam dampers do. Although the above-mentioned designs of dampers have led to progress at some points, they also made the structure coupling beams complicated enough to hardly justify the improvements in the energy dissipation capacity. In addition, parameter optimization which can potentially improve damper performance is often overlooked in the design of coupling beam dampers.  
To this end, we proposed a two-fold method for the design of a simple and easy-to-make metallic damper that features a high energy dissipation capability. Based on the existing dampers, four types of openings in the damper are developed and studied. A constitutive law is provided to establish the relationship between design parameters, including the opening size and thickness, and the energy dissipation capacity. A Kriging surrogate model is then introduced with a shuffled complex evolution (SCE) intelligent optimization algorithm to search the optimized design parameters that can lead to the maximum hysteresis energy. The proposed work can also be used as a platform for opening parameter design with high surrogate accuracy and global optimization efficiency.