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Aeolian vibration of conductors could cause extensive damages to the electric power transmission networks. The use of Stock-Bridge dampers is a very common method to control the transmission line vibration amplitude. Due to the complexity of the cable-wind interaction, the Energy Balance Method (EBM) is extensively used for calculating the steady state amplitude of the system. In the present study EBM incorporating the traveling wave method are developed for calculating the steady state amplitude of the cable with arbitrary number of dampers. The wave propagation was produced by superposition of two travelling waves. The proposed method is subsequently employed to study the effect of the number, location and impedance of dampers on dissipated energy and damper performance as well. The results show that damper installation at optimum location is more effective than the damper number increase, in which case does not necessarily leads to the dissipated energy increase. Furthermore, in this study a simple equation relating ISWR (Inverse Standing Wave Ratio) to Absorption Coefficient is introduced. The importance of this equation is due to the fact that only ISWR can be readily measured, but not the absorption coefficient itself, which is based upon the measurement of the travelling wave amplitudes. Finally, investigation on damper dynamic characteristics effects on absorption coefficient reveals that the real parts of damper impedance having complete absorption is independent of vibration frequency; and if the magnitude of damper impedance be lower than that of the cable for all the frequency range, complete absorption will never occur.

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Base isolation is an effective technology for reducing seismic damage to structural and non-structural components as well as building contents, allowing buildings to maintain their function during and after a rare, high-intensity earthquake. This makes it an ideal seismic response correction system for importance buildings. The main advantage of isolated structures is that seismic responses can be easily and effectively reduced by prolonging the period and increasing damping. Therefore, the natural period of the structure isolated from the base is longer. In this paper, a new energy balance method is used to design a lead rubber bearing (LRB) isolator. Energy balance method is an analysis method to evaluate seismic resistance based on the balance of seismic energy input to buildings due to ground motion and energy absorbed by the building. In other words, the energy balance method is a response prediction method to approximate the seismic response of buildings isolated from the foundation. This method is effective for determining the relationship between ground motion, seismic isolation period and the effect of reducing the reaction of dampers. In this method, the specifications of the isolation system, including stiffness, yield shear force and viscous damping ratio, are adjusted in such a way that the maximum shear and maximum displacement in the isolation system do not exceed a certain value determined by the designer. This allows the designer to limit the maximum displacement at the isolation level to a certain amount when there is a constraint on the supply of separation distance around the building and the isolated level. Also, by limiting the maximum shear of the isolators, it is possible to use the base isolation system for retrofitting the existing structures that have a certain lateral capacity.
This design method was first proposed and used in Japan. This method has been recently proposed in the Iranian regulations (which is being drafted) and has not been used much in this country so far. Its advantages include no need for trial and error in the design process, the possibility of designing a rubber and frictional type of seismic isolator, the possibility of using a viscous or hysteretic damper, or a combination of both at the isolator installation site. To evaluate the accuracy of this method, three 5, 10 and 15-story steel structures with an ordinary concentric braced frames in both directions for clinic usage have been modeled and under eight near and far-field earthquakes in the by the nonlinear time-history analysis method have been analyzed. The results obtained from the time-history analysis are in good agreement with the estimated results of the energy balance method. The error percentage related to the displacement of isolator compared to the value assumed at the beginning of the design for 5, 10 and 15-story structures is 3.4%, 2.57% and 2.12%, respectively. Also, the percentages of error related to the maximum shear of isolator compared to the value obtained from the performance curve for 5, 10 and 15-story structures are 11.08%, 12.61% and 13.98%, respectively.