Smart Passive Damper Design for Building Structures with Higher Resilience Under Uncertain Earthquake Ground Motions

Existing and new building structures located in earthquake-prone areas are vulnerable to damages. One 16 strategy to protect these structures is to incorporate supplemental energy dissipation devices, in the 17 form of hysteretic, viscous, or inertial dampers. In the last few years, these devices demonstrated their 18 capability to limit earthquake-induced damage, thus implying minimal downtime and affordable repair 19 cost in both ordinary and strategic/critical building structures. However, the efficiency of such devices 20 strongly relies on their appropriate placement in the building structure as well as in the selecting their 21 constitutive parameters. Another open issue is to incorporate the uncertain nature of the seismic 22 excitation within a robust design framework. A smart design strategy using passive dampers should 23 account for the peculiar characteristics of the structure and should aim at achieving multi-level 24 performance requirements under different levels of excitation through robust multi-objective 25 optimization. 26Based on these motivations, this Research Topic has collected seven papers after a detailed and 27 rigorous peer-review process. The papers deal with smart passive damper design that explicitly 28 incorporates the uncertainty of the seismic excitation or structure, simultaneous optimal design of main 29 building structures and dampers under critical seismic excitation, innovative energy dissipation 30 technologies and hybrid dampers for an improved earthquake-resilient building design and smart 31 damper optimization under long-period pulse-type ground motions of extremely large amplitudes. 32Hashizume and Takewaki examined the performance of a novel hysteretic-viscous hybrid (HVH) 33damper system for the seismic protection of tall buildings. The system combines a large-stroke viscous 34 damper with a hysteretic damper equipped with a gap mechanism as a stopper. The proposed system This is a provisional file, not the final typeset article was adopted to mitigate catastrophic effects caused by long-period pulse-type earthquake ground 36 motions of extremely large amplitudes, which may be particularly critical for high-rise and base-37 isolated buildings with a long natural period. The authors used a double impulse as representative of 38 the main part of pulse-type ground motions of extremely large amplitude. The HVH damper system 39 proved to be an effective strategy to reduce the catastrophic effects of this kind of seismic excitation 40 on tall buildings and exhibited a comparable performance to a formerly proposed dual hysteretic 41 damper (DHD) system composed of parallel-type small and large-amplitude hysteretic dampers. 42Hishida and Takewaki further explored the optimal design of the previously described HVH damper 43 system when implemented in nonlinear building frames for simultaneous reduction of interstory drift 44 and acceleration. Although the HVH is effective in mitigating the deformation response (interstory 45 drift), as a counter effect, it increases the acceleration response when the gap mechanism becomes 46 active (stiffness starts working). For this reason, a compromise between the reduction of maximum 47 interstory drift and maximum acceleration was sought by the authors. A combined index performance 48 parameter was introduced that simultaneously accounts for maximum interstory drift and maximum 49 acceleration, which was minimized to obtain the optimal gap quantity of hysteretic dampers with gap 50 mechanism for various input velocity levels and various hysteretic damper stiffness ratios. 51 Fujita et al. investigated the optimal damper placement for building structures under the resonant 52 critical double impulse, as representative of actual earthquake ground motions. In this work, the authors 53 incorporated the influence of uncertain characteristics of linear and bi-linear oil dampers and of 54 stiffness of the building frame on the resulting building structural safety. A robust optimization method 55 was proposed by changing the second impulse timing, thus considering inherent uncertainties in input 56 seismic excitation. Moreover, a novel objective function was conceived to enhance the structural 57 performance and robustness. Numerical examples on 10-and 20-story planar building frames 58 demonstrated higher robustness of the structural performance by using the proposed approach as 59 compared to an alternative, ordinary optimal damper placement without considering uncertainties. 60Takewaki and Akehashi presented a comprehensive and systematic review of the optimal and smart 61 design of nonlinear building structures with and without passive dampers subjected to earthquake 62 loading. Different aspects were discussed in this review through a sixfold categorization approach: 1) 63 the optimal design of bare nonlinear building frames under seismic loading; 2) the optimal design of 64 nonlinear dampers for elastic building frames under seismic loading; 3) the optimal design of linear 65 dampers for nonlinear building frames under seismic loading; 4) the optimal design of nonlinear 66 building frames with specified nonlinear dampers under seismic loading; 5) the optimal design of 67 nonlinear dampers for specified nonlinear building frames under seismic loading; and 6) the 68 simultaneous optimization of elastic-plastic building structures and passive dampers. This 69 categorization provided an overview of how literature studies are advancing gradually by accounting 70 for nonlinear responses, and also introduced another classification in view of solution strategies 71 proposed by researchers, including mathematical programming approaches, optimality criteria 72 approaches, metaheuristic approaches and a combined approach of the sensitivity-based procedure and 73 the optimality criteria. 74 Uemura et al. addressed the global simultaneous optimization of oil, hysteretic and inertial dampers 75 for building structures using a real-valued genetic algorithm and local search. By means of the proposed 76 simultaneous optimization method, structural designers are given the possibility of selecting the 77 optimal proportion of these three dampers based on cost and performance requirements. Displacement 78 and acceleration response can be reduced well by oil dampers without implying significant changes in 79 natural frequencies, while hysteretic dampers reduce displacement but may increase acceleration response. Finally, inertial dampers can lengthen the natural periods with negative stiffness and reduce 81 the maximum acceleration but, as a counter effect, may lead to some undesired increase of deformation. 82Considering these peculiar aspects of each damper, the authors used a real-valued genetic algorithm 83 optimization algorithm to attain a global optimal solution. A multi-objective optimization for 84 deformation and acceleration was also investigated. It was demonstrated that the proposed approach 85 leads to the best solution by involving a relatively short computational time (smaller number of time-86 history response analyses than an alternative sensitivity-based algorithm). 87Akehashi and Takewaki presented a new method for the simultaneous optimal design of main building 88 structures and viscous dampers for elastic-plastic building structures under critical double impulse. By 89 assuming the maximum interstory drift as the objective function, the most inactive story stiffness and 90 damper damping coefficients were sequentially eliminated in the optimal design procedure. It was 91 demonstrated that the proposed sensitivity-based design algorithm is effective irrespective of the target 92 value of the sum of damper damping coefficients and the input level of the critical double impulse. In 93 particular, by the numerical analyses presented, it emerged that the proposed design method enables 94 the high yield-strength design with effective seismic energy absorption and the high limit-strength 95 design effective for extremely large disturbances. 96 Kawai and Takewaki investigated the critical response of a multi-story damped bilinear hysteretic shear 97 building model under a multi-impulse representative of long-period, long-duration earthquake ground 98 motions. The critical input timing of the multi impulse was identified as the time in which the story 99 shear force (sum of the restoring force and the damping force) in the first story attains zero in the 100 unloading process. A so-called Multi Impulse Pushover (MIP) was introduced to perform a 101 comprehensive performance evaluation for increasing input levels. In the MIP, once the critical time 102 interval between impulses in the multi impulse was found for a specific input level, the input level is 103 increased gradually and a new critical timing is determined. This procedure is repeated until reaching 104 the desired input level. The performance evaluation was conducted in terms of energy response 105 indicators, and compared to the response under a sinusoidal wave to demonstrate the usefulness of the 106 adopted multi impulse as a substitute of sinusoidal waves. 107