非弾性鉄筋コンクリート造建物に設置する地震用TMDの最適同調比

<p> This paper discusses tuned mass damper (TMD) for reducing seismic response in reinforced concrete buildings. Optimal tuning ratios are estimated using equivalent two-degree-of-freedom systems through time history analysis. A formula for calculating the optimal tuning ratio is proposed in terms of the envelope curve of the restoring force and ductility factor of buildings. This formula is applicable to buildings with a wide range of natural period and soil classes for historical ground motions with an inherent complex response spectrum. Finally, a numerical example is demonstrated for buildings subjected to long-period ground motions to show the effectiveness of TMD.</p><p> In recent years, tuned mass dampers (TMD) have been applied to steel buildings for reducing seismic response in Japan. Although TMDs are also expected in reinforced concrete buildings, a tuning strategy is difficult for such highly nonlinear structures. This paper discusses the optimization of TMDs applied to nonlinear structures using time history analysis.</p><p> In Chapter 2, we propose an equivalent two-degree-of-freedom (2-DOF) system for computationally efficient optimizations. A combination of modal coordinate and physical coordinate is employed for a TMD connected to a building. To meet a compatibility condition, we present a computational method with a modified envelope curve of building hysteresis and a quasi external force applied to the TMD. This technique allows commercial software to compute the response of the 2-DOF system.</p><p> In Chapter 3, it is shown that the proposed 2-DOF system gives almost the same response with a corresponding original vibratory system. This 2-DOF system demonstrates response surfaces consisting of design parameters of a TMD, using a building having twenty-five stories. If an elastic-based optimal damping ratio of a TMD is used, control performance is approximately the same as the exact optimal TMD. This study, therefore, focuses on a tuning ratio, which specifies optimal stiffness.</p><p> In Chapter 4, optimal tuning ratios accompanied with gradually amplified ground motions are estimated using time history analysis with simulated ground motions. We formulate a closed-form of optimal tuning ratios based on equivalent natural period and a mass ratio, which is a relative mass of the TMD to the building. If the envelope curve of a controlled building and is specified, the optimal tuning ratio is obtained according to the peak ductility factor. Thus, an optimal TMD depends on seismic intensity. This formula is applicable to a wide variety of yield ratios, natural period, and the predominant period of the soil.</p><p> In Chapters 5 and 6, it is shown that the proposed formula is also applicable to buildings subjected to historical ground motions and long-period ground motions that are generated by assuming a Nankai-Trough earthquake.</p><p> Findings obtained by this study allows us to estimate an optimal TMD without iterative time history analyses. It is also useful to assess the seismic effectiveness of a TMD applied to a reinforced concrete building.</p>