## 1 Editorial
Performance-based optimization of the TMDI and the TID is carried out to find a good trade-off between displacement and acceleration-response mitigation, with the installation floor being an explicit design variable, in addition to frequency and damping ratio, and considering different wind directions. The authors demonstrate that the optimally designed TMDI/TID can achieve better wind-induced vibration mitigation than the conventional tuned mass damper (TMD), while allocating lower or null attached mass, especially in terms of acceleration response. In paper [4], [PERSON] et al. propose a displacement-dependent damping inerter system (DDIS) for seismic response control. This configuration is alternative to conventional configurations of commonly used inerter systems utilizing a velocity-dependent damping. The proposed configuration implies a displacement-dependent element (DDE) in parallel to the inerter device and in series with a tuning spring, which is found to generate a larger control force in the early stage of excitation in comparison to a viscous-damping inerter system (VDIS). The DDE is governed by a bilinear elastoplastic constitutive behavior. Although in this paper the analysis is limited to a SDOF system equipped with the proposed DDIS, the authors demonstrate the influence of various DDIS-parameters through a wide parametric study based on stochastic dynamic analysis. The stochastic linearization method is used to handle the nonlinear terms, and three performance indicators related to the displacement, acceleration and filtered energy response are analyzed. Then, the seismic response is evaluated in the time domain, taking the non-linearity into account and considering both artificial and natural records. It is found that the interaction between inerter, spring and the DDE is particularly effective for the structural control. The inerter amplifies the deformation of the DDE in the DDIS by over 60%; thus, the DDIS is characterized by a higher energy dissipation capability, namely as damping enhancement effect. Because of the damping and mass-enhancement mechanism, the proposed DDIS considerably reduces the structural displacement and acceleration, and is more effective than a VDIS especially the early stage of the seismic response. In paper [5], [PERSON] et al. investigate, from an experimental and numerical point of view, a novel curved steel plate damper to improve the seismic performance of structures. Analytical formulae to determine the key design parameters of the damper, namely elastic stiffness, yield strength, and yield displacement, are derived. Experimental tests are carried out on four prototypes of metallic dampers, characterized by different geometric properties, so as to identify the most effective combination of parameters in terms of stability of hysteresis and energy dissipation performance. Finite element simulations are also performed to simulate the loading process of the specimens, to investigate the strain and stress distributions and to validate the design formulae proposed in this research work. In paper [6], [PERSON] et al. propose a two-degree of freedom tuned mass damper (2 DOFs TMD) for vibration mitigation of a suspension bridge. The simultaneous action of the two TMDs makes it possible to control both bending and torsional modes of the bridge deck. Parameters of the proposed 2 DOFs TMD are optimized through a control problem, with decentralized static output feedback for minimizing the response of the bridge deck, and a graphical approach is introduced to arrange flexible beams properly according to the exact constraints. It is found that the synthetic approach, based on both the graphical approach and parameterized compliance, is an effective way to design the TMD with the expected DOFs, in order to accomplish expected modes. Moreover, experimental findings on a small scale prototype demonstrate the ability of the TMDs of suppressing several vibration modes under laboratory conditions. In paper [7], [PERSON] et al.