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Ishimaru S.,I2S2 Co. | Hata I.,Nihon University | Mikami J.,NihonUniversity | Kimiduka M.,I2S2 Co.
Journal of Structural and Construction Engineering | Year: 2010

This paper presents a simple design method for tuned dynamic mass systems (T.D.M.S.) consisted of dynamic mass-viscous damper-spring devices. The systems are designed by the law of geometric mean as a tuning rule, which is derived from the properties of the invariant point theory. The paper indicates that performance of the structure basically depends on the auxiliary stiffness factor which is the ratio of the stiffness of the devices to that of the main structure. And it also shows that the structures with T.D.M.S. can easily hold viscous damping factors more than 0.20 for the 1s t and 2 n d modes, when the auxiliary stiffness factor is controlled more than 0.25.


Hirotani N.,Nihon University | Ishimaru S.,I2S2 Co. | Furuhashi T.,Nihon University
Journal of Structural and Construction Engineering | Year: 2015

This paper presents performance based design diagrams to estimate cumulative responses, as well as maximum responses of bilinear hysteretic systems by making use of triple elastic response spectra. The 2011 Great East Japan earthquake9)-11) forced us miserable experience which caused havoc over many villages and city areas located along the Pacific coast of East Japan due to the great seismic sea waves, and also caused destruction of a large number of buildings in inland areas by severe ground motions with the very long durations more than ten minutes. Many areas suffered severe ground motions equivalent to JMA (Japanese Meteorological Agency) Seismic Intensity Scale (SIS) 7 from which structural designers have been kept away as unexpected events. Thus, it is strongly required to meet the demands of the times which the design standards should be raised also from the view point of Tokai, Tonankai and Nankai-coupled earthquake predicted in the near future. One of them is the development of design procedures for response control structure systems with high performance devices such as viscous dampers, elasto-plastic dampers and dynamic mass dampers. As an example of them, S. Ishimaru etc. have presented and freely opened the performance based design diagrams13), 14), 20), 21) which are able to estimate maximum deformation and velocity of a single degree of freedom system with elasto-plastic dampers and viscous dampers through the two spectra pSv,40 and Sv,40 of an elastic system for a target ground motion. The symbols pSv,40 and Sv,40 are the pseudo velocity spectrum (the product of circular frequency and deformation) and velocity spectrum of the system. In this paper, the diagrams are developed to newly evaluate cumulative plastic deformations which are very important in judging structural safety from a view point of fatigued collapse1)-8). In the same way to the previous diagrams, the concept of separated variables of a spectrum is applied, which is able to make Eq. (14) hold. That is, hysteretic energy spectrum VE,D(T') for a target ground motion (refer to Eq. (12), μc: cumulative ductility factor) can be expressed by the product of input energy spectrum of a structure with damping ratio 40% V¯E,40(T') (refer to Eqs. (10) and (11)) and empirical formulas ζ¯VE(h, μd,pd) (refer to Eqs. (15), (17) and (ap-l)) and ζ¯Dc(h, μd, pd) (refer to Eqs. (19), (20) and (ap-2)) including the parameters of viscous damping ratio h, ductility factor μd and bilinear stiffness factor pd. The empirical formulas are formed by the method of least squares for the statistical response results for the combination cases 239,400 between the damper parameters shown in Table 1 and the applied ground motions shown in Table 2. The correctness of the hypothesis of Eq. (14) is shown in Fig. 5-b). Some examples of the diagrams are shown in Figs. 11, 12 and 15 as the relations between (D¯c/D40) and (Dmax/D40), in which the symbols D¯c and Dmax are the cumulative plastic deformation and the maximum deformation, respectively. The symbol D40 is the spectral deformation at an effective period T' (refer to Eq. (2)) for the pseudo velocity spectrum. The accuracy of the diagrams is shown in Fig. 9, which is examined by non-linear time history analyses of 239,400 cases. The results show that specifying viscous damping ratio h, ductility factor μd and bilinear stiffness factor pd, the maximum deformation, velocity and cumulative plastic deformation can be easily evaluated by the combination of the proposed design diagrams and three elastic spectra pSv,40, Sv,40 and V¯E,40.


Ishimaru S.,I2S2 Co. | Hata I.,Nihon University | Miyajima Y.,I2S2 Co. | Mikami J.,I2S2 Co.
Journal of Structural and Construction Engineering | Year: 2012

This paper presents a procedure named ductility factor control method for moment-resisting frames with tuned dynamic mass systems. The objective is to estimate yield moments and other parameters satisfying target performances such as ductility factors for structural elements and viscous damping ratios for its system. This is a new version of the original paper presented by Ishimaru in 1975, which consists of a pseudo modal analysis making use of the combination between time history waves of nonlinear SDOF systems as modal coordinates and their participation vectors regarding to structural elements. The numerical examples show that the method is able to facilitate its implementation in practical design with high accuracy.


Kuo C.,Nihon University | Ishimaru S.,I2S2 Co. | Furuhashi T.,Nihon University | Hata I.,Nihon University
Journal of Structural and Construction Engineering | Year: 2013

This paper presents a design method for super high-rise structures with tuned dynamic mass systems. After the 1995 Southern Hyogo Prefecture Earthquake and the 2011 off the Pacific coast of Tohoku Earthquake, it becomes very important to design response control structures against two types of coherent earthquake ground motions such as long period waves and pulse waves. This paper discusses the performance of structures which are designed by making use of tuned dynamic mass systems against these ground motions having JMA seismic intensity scale 6upper or 7.


Ishimaru S.,I2S2 Co. | Hata I.,Nihon University | Furuhashi T.,Nihon University
Journal of Structural and Construction Engineering | Year: 2011

This paper presents a simple design method for tuned dynamic mass systems, which are adjusted by a concept of pseudo mode control. The intension of the pseudo mode control is to make the target structure practically behave as a SDOF system by suppressing the growth of a few higher modes such as the second mode and the third mode. Since giving high viscous damping has a tendency to stimulate the growth of higher vibration modes, the optimum damping tuning is decided by comparing the effect of mode control with the magnitude of the viscous damping factor on a basis of the invariable point theory for a SDOF system. The paper shows that the presented structure system is able to hold the viscous damping factors more than 0.15, when the auxiliary stiffness factor defined by the invariable point theory is controlled more than 1/1.5.


Ishimaru S.,I2S2 Co. | Mikami J.,Nihon University | Hata I.,Nihon University | Furuhashi T.,Nihon University
Journal of Structural and Construction Engineering | Year: 2010

This paper introduces a simple design method for tuned dynamic mass(D.M.) systems with very large added mass ratio which is the value of D.M.(rotating inertial mass) to mass of the main structure. The method is constructed on the bases of rule of geometric mean and rule of difference/sum for the natural periods computed under the particular conditions of viscous damping factors of hd = 0 and hd = . The rules are derived from the properties of the invariant point theory. The paper shows that the structures can be designed by the proposed method, which hold viscous damping factors more than 0.2 for the 1st and 2nd modes.

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