Discussed reasonable damping ratio in low amplitude vibration and strong vibration, by the relationship of basic vibration modal and other modals, the Revised Rayleigh damping modal is presented , and the method of damping ratio calculation in complex damping structure is discussed.

For new energy dissipation buildings, this article points out that the effect of additional damping ratio should be taken into consideration in the design of the structure before installation of dampers by the application of mode-superposition response spectrum method.

The dynamic shear modulus and damping ratio are calculated by the formulas (l)and (2),proposed originally by Hardin & Drnevich and revised by author considering simultaneous action of the dynamic normal stress and shear stress with introducing a parameter of coativity W.

The damping will be defined by the shear damping ratio for the soil D, analogous to the critical viscous damping ratio for a single degree of freedom c/c0.

Thus, only two tests would be necessary in order to obtain both the maximum damping ratio, introduced by the piezo device, and the natural frequency of the whole system.

Therefore, several tests (experimental or numerical) ought to be carried out in order to determine the resistor which provides the maximum damping ratio for a mode of interest, and in turn the natural frequency of the whole structure.

A damping ratio of less than 0.05 percent of critical damping is proved to be valid for the aluminum panel.

The modal damping ratio is improved from below 0.2 percent to above 4 percent.

The visco-elastoplatic soil model, introduced in this paper, is consistent with the experimental relationships, such as shear modulus vs shear strain, damping ratio vs shear strain, pore pressure ratio vs cycle ratio and stress ratio vs number of liquefaction cycles, etc. The loading-reloading rules control the hysteresis loops beneath skeleton curve. The "apparent applied forces"method is suggested to evaluate the effects of soil viscosity. The generations of pore pressure are evaluated...

The visco-elastoplatic soil model, introduced in this paper, is consistent with the experimental relationships, such as shear modulus vs shear strain, damping ratio vs shear strain, pore pressure ratio vs cycle ratio and stress ratio vs number of liquefaction cycles, etc. The loading-reloading rules control the hysteresis loops beneath skeleton curve. The "apparent applied forces"method is suggested to evaluate the effects of soil viscosity. The generations of pore pressure are evaluated by"fraction cycle method", which is simple and effective, especially for waved increases of pore water pressure.The soil model have been applied to a computer program (SRHSL-1978) for the total stress analysis of seismic response of site soil.

Simulating earthquake loading conditions, a series of cyclic triazial compression tests was carried out on undisturbed samples of cohesive soils from Tianjin so as to investigate the dynamic shear modulus and damping ratio. It has come to the conclusion that the variation of damping ratio, as well as shear modulus, with strain amplitude can be expressed by an empirical formula. The normalized form of shear modulus vs. strain amplitude will be shown by a single curve, and that of damping ratio...

Simulating earthquake loading conditions, a series of cyclic triazial compression tests was carried out on undisturbed samples of cohesive soils from Tianjin so as to investigate the dynamic shear modulus and damping ratio. It has come to the conclusion that the variation of damping ratio, as well as shear modulus, with strain amplitude can be expressed by an empirical formula. The normalized form of shear modulus vs. strain amplitude will be shown by a single curve, and that of damping ratio vs. strain amplitude by a family of curves or a band zone with shrunk ends. The view-point about the law of damping ratio varying with strain amplitude has been developed. A comparison between the measured values from laboratory test and those based on seismic survey for the elastic modulus has been made, and a reasonable agreement has been obtained. For some of cohesive soil strata in Tianjin, some data available for seismic analyses have been provided.

Based on the assumption of undrained behavior, author has proposed previously a finite element method for calculating the pore pressure and permanent deformation of saturated sands during earthquake.In this paper, the method is extended to including both generation and dissipation of pore pressure coupled with deformation under two dimensional condition.The analytical procedure consists of earthquake stage and post-earthquake stage, and each stage is subdivided into several time steps. For the first stage, both...

Based on the assumption of undrained behavior, author has proposed previously a finite element method for calculating the pore pressure and permanent deformation of saturated sands during earthquake.In this paper, the method is extended to including both generation and dissipation of pore pressure coupled with deformation under two dimensional condition.The analytical procedure consists of earthquake stage and post-earthquake stage, and each stage is subdivided into several time steps. For the first stage, both dynamic response analysis and static analysis are required for every time step, but the static analysis only is necessary for post-earthquake stage.The dynamic analysis is based on equival; ent nonlinear viscous-elastie midel, similar to that proposed by Idriss and Seed in their programm QUAD4, and the static analysis is made in the way as that of Biot's consolidation theory for clay. The dynamic shear modulus and damping ratio are calculated by the formulas (l)and (2),proposed originally by Hardin & Drnevich and revised by author considering simultaneous action of the dynamic normal stress and shear stress with introducing a parameter of coativity W. From dynamic analysis, the residual volumetric and shear deformation increments are obtained according to the constitutice relationships (5) and(6), in wich N and AN are the equivalent number of uniform cycles and its increment, γd and ρd are the dynamic shear strain amplitude and dynamic normal stress amplitude, δ is a measure of asymmetry of the dynamic shear stress, and C1,C2,C3,C4, G5 are five constants.In the static analysis, the initial strain method is used, hence the above mentioned volumetric and shear deformation increments are converter! to fictive nodal forces.A response analysis of a sand layer to horizontal bed rock motion is given as an illustration.