Bio: Kiyoshi Kanai is an academic researcher. The author has contributed to research in topics: Empirical formula. The author has an hindex of 1, co-authored 1 publications receiving 445 citations.
Topics: Empirical formula
25 Sep 1957
TL;DR: In this paper, a study on the optimal design of a TMD for a single-degree-of-freedom structure under seismic loads was conducted in which the floor decks and isolation system together can be viewed as a giant tuned mass damper to reduce the seismic force of the truss.
Abstract: In seismic retrofit of a long-span truss bridge in Japan, a new retrofit scheme was applied in which the existing bearings of the bridge were replaced by a new floor deck isolation system. The floor decks and isolation system together can be viewed as a giant tuned mass damper (TMD) to reduce the seismic force of the truss. This motivates a study on the optimal design of a TMD for a single-degree-of-freedom structure under seismic loads in this paper. Kanai–Tajimi spectrum is selected to model the earthquake excitation. It is shown that, when ratio of the characteristic ground frequency in the Kanai–Tajimi spectrum to the structural frequency is above three, the ground motion can be assumed to be a white noise to design TMD. For a smaller ground frequency ratio, simple formulas of the optimal TMD parameters are obtained. The dependence of optimal TMD parameters on mass ratio especially for large TMD is highlighted. It is found that the optimal TMD has lower tuning frequency and higher damping ratio as the mass ratio increases. For a large mass ratio, TMD becomes very effective in minimizing the primary structure response and robust against uncertainties in the parameters of the system.
TL;DR: The review clearly demonstrates that the TMDs have a potential for improving the wind and seismic behaviors of prototype civil structures and shows that the MTMDs and d-MTMDs are relatively more effective and robust, as reported.
Abstract: A state-of-the-art review on the response control of structures mainly using the passive tuned mass damper(s) (TMD/s) is presented. The review essentially focuses on the response control of wind- and earthquake-excited structures and covers theoretical backgrounds of the TMD and research developments therein. To put the TMD within a proper frame of reference, the study begins with a qualitative description and comparison of passive control systems for protecting structures subjected to wind-imparted forces and forces induced due to earthquake ground motions. A detailed literature review of the TMD is then provided with reference to both, the theoretical and experimental researches. Specifically, the review focuses on descriptions of the dynamic behavior and distinguishing features of various systems, viz. single TMD (STMD), multiple tuned mass dampers (MTMDs), and spatially distributed MTMDs (d-MTMD) which have been theoretically developed and experimentally tested both at the component level and through small-scale structural models. The review clearly demonstrates that the TMDs have a potential for improving the wind and seismic behaviors of prototype civil structures. In addition, the review shows that the MTMDs and d-MTMDs are relatively more effective and robust, as reported. The paper shows the scope of future research in development of time and frequency domain analyses of structures installed with the d-MTMDs duly considering uncertainties in the structural parameters and forcing functions. In addition, the consideration of nonlinearity in structural material and geometry is recommended for assessment of the performance of the STMD, MTMDs, or d-MTMDs.
TL;DR: In this paper, the authors address the topic of the spatial variation of seismic ground motions as evaluated from data recorded at dense instrument arrays, focusing on spatial coherency and its interpretation.
Abstract: This study addresses the topic of the spatial variation of seismic ground motions as evaluated from data recorded at dense instrument arrays. It concentrates on the stochastic description of the spatial variation, and focuses on spatial coherency. The estimation of coherency from recorded data and its interpretation are presented. Some empirical and semi-empirical coherency models are described, and their validity and limitations in terms of physical causes discussed. An alternative approach that views the spatial variation of seismic motions as deviations in amplitudes and phases of the recorded data around a coherent approximation of the seismic motions is described. Simulation techniques for the generation of artificial spatially variable seismic ground motions are also presented and compared. The effect of coherency on the seismic response of extended structures is highlighted. This review article includes 133 references. @DOI: 10.1115/1.1458013#
TL;DR: In this paper, the performance of a nonlinear tuned mass damper (NTMD) was investigated using the numerical continuation software AUTO and the optimization of periodic solutions and parameter sweeps.
Abstract: We explore the performance of a nonlinear tuned mass damper (NTMD), which is modeled as a two degree of freedom system with a cubic nonlinearity. This nonlinearity is physically derived from a geometric configuration of two pairs of springs. The springs in one pair rotate as they extend, which results in a hardening spring stiffness. The other pair provides a linear stiffness term. We perform an extensive numerical study of periodic responses of the NTMD using the numerical continuation software AUTO. In our search for optimal design parameters we mainly employ two techniques, the optimization of periodic solutions and parameter sweeps. During our investigation we discovered a family of detached resonance curves for vanishing linear spring stiffness, a feature that was missed in an earlier study. These detached resonance response curves seem to be a weakness of the NTMD when used as a passive device, because they essentially restore a main resonance peak. However, since this family is detached from the low-amplitude responses there is an opportunity for designing a semi-active device.
TL;DR: In this paper, a simplified seismic design procedure is proposed for structures equipped with an innovative friction-damping system, which has been shown experimentally to perform very well and could represent a major new development in earthquake-resistant design.
Abstract: A simplified seismic design procedure is proposed for structures equipped with an innovative friction-damping system. The system has been shown experimentally to perform very well and could represent a major new development in earthquake-resistant design. This paper first presents an efficient modeling approach for the seismic analysis and design of friction-damped structures. The hysteretic properties of the friction dampers are derived theoretically and are included in a Friction Damped Braced Frame Analysis Program (FDBFAP), which is adaptable to a microcompter environment. FDBFAP is then used to perform a parametric study of the optimum slip-load distribution for the friction dampers. The results of the study lead to the construction of a design slip-load spectrum for the rapid evaluation of the optimum slip-load distribution. The spectrum takes into account the properties of the structure and of the ground motion anticipated at the construction site. The availability of this design slip-load spectrum should lead to a greater acceptance by the engineering profession of this innovative design concept.