Time-domain constitutive model based on logarithmic skeleton curve and its application

The equivalent linearization method for seismic nonlinear response of soils will overestimate its high-and low-frequency nonlinear effects, and the plastic deformation of soils can not be reflected, especially for soft soil layer sites and thin overburden sites. The functional expression for logarithmic skeleton curves is proposed based on the test curves to analyze the time-domain nonlinear seismic responses, and the characteristic of the new skeleton curve is that the asymptote rises slowly. Based on the Mashing criterion, a logarithmic dynamic skeleton constitutive model is established with loading-unloading turning points as reference points. On this basis, a 1D time-domain seismic response method for soil by using the overlapping difference scheme is proposed. The corresponding program Soilresp1D is developed taking Microsoft Visual C++ 6.0 as the platform, and it is used to analyze the nonlinear seismic response of soft-soil layer sites and thin overburden sites and Eureka Canyon Road site. By comparing with the results of time-domain analysis based on the hyperbolic dynamic skeleton constitutive model, the equivalent linearization analysis and the actual seismic response observation, the feasibility and rationality of the proposed logarithmic dynamic skeleton curve are verified. The results show that the nonlinear seismic response method based on the logarithmic dynamic skeleton constitutive model can be applied to the seismic response analysis of different soil-layer sites. It is especially shown that the area of the hysteresis loop of the logarithmic dynamic skeleton curve and the damping degradation coefficient are larger, thus the damping effect and the plastic property of soils are better reflected.