## 1 Editorial  
Civil engineering structures and infrastructures are inherently vulnerable to exceptional loads related to natural disasters, primarily earthquakes, tsunamis, strong winds, and floods. Consequently, one of the major challenges in the structural engineering field for the last decades has been to conceptualize, develop, and implement effective protective systems to mitigate such vulnerability, and to improve structural robustness and resilience. Base isolation and passive energy dissipation systems have demonstrated their effectiveness in coping with different kinds of environmental forces, including earthquakes and winds, as documented in theoretical and numerical studies and shaking table tests, as well as evidence from how they actually behaved during real catastrophic events. These structural protective systems traditionally include elastomeric bearings, lead rubber bearings, sliding friction pendulum, and various kinds of dampers, such as metallic, viscous, viscoelastic, friction dampers, tuned mass dampers and tuned liquid dampers. The working mechanism underlying the aforementioned technologies is well known, and basic methods for their rational design and implementation are well established. Notwithstanding, there is an ever-growing interest in developing novel analytical and/or numerical tools to design structures equipped with optimally configured devices. Indeed, the design of such devices benefits from the current state-of-the-art algorithms and solvers for their optimization, which are constantly evolving. Other recent advances in this field concerns the development of cutting-edge models to reliably capture a series of complex nonlinear phenomena characterizing the hysteresis of such devices, calibrated based on experimental findings. On the other hand, the family of devices and dissipative elements for structural control keeps broadening due to the increasing performance demands of structures and due to new progress achieved in material science and mechanical engineering. In this context, recent advances include new strategies to develop the concept of energy dissipation into innovative devices, including negative stiffness devices, inerter-based systems, low-cost replaceable systems and dampers with a phased behavior. Although the development of new technologies generally follows established practice and underlies basic working principles, existing design methods for conventional devices are not always straightforwardly applicable to these new devices. Thus, there is an urgent need for revisiting design methodologies for such emerging technologies. Other significant contributions concern the development of hybrid protective systems based on energy dissipation devices that are conventional in their working mechanism, but that are combined together in a non-conventional arrangement so that their dynamic behavior is more effective than existing technologies. Following these research motivations, this Special Issue collects 13 papers focused on structural protective systems applied to structures and infrastructures, including both traditional and innovative devices, using conventional and advanced design methodologies. In the Editors' opinion, each article contains undisputable scientific novelties from various perspectives (analytical, numerical, experimental, conceptual, implementation issues), proposes benchmark or emblematic engineering projects, and represents a major contribution in the design of structures with passive energy dissipation systems. The Editors hope that this article collection can somehow contribute, even if modestly, to the continuous research for more effective mitigation of the risks that natural disasters pose to humankind. Some papers in the Special Issue concern the development of inerter-based vibration control strategies, and their deployment in civil engineering structures and infrastructures.