Cyclic Elasto-plastic Model Research Articles

Large deformation and failure analysis of river embankments subjected to seismic loading

A numerical model based on the theory of mixtures is proposed for the nonlinear large deformation and failure analysis of river embankments subjected to large earthquakes. The governing equations are discretized using the finite element method in large deformation regime with the updated Lagrangian description. A cyclic elasto-viscoplastic model is used for describing the rate-dependent behavior of clayey soils, while a cyclic elasto-plastic model is adopted for sand. The nonlinear kinematic hardening and softening due to structural degradation of soil particles are taken into account in the constitutive relations. Efforts have been made to model the failure modes and damage patterns of river embankments observed in the 2011 Tohoku Earthquake. The effects of ground profile, water table, and earthquake motion on the dynamic response and damage pattern of river embankments are particularly emphasized.

A cyclic elastoplastic constitutive model and effect of non-associativity on the response of liquefiable sandy soils

A large number of constitutive models for geomaterials, such as soils and rocks, have been proposed over the last three decades. Those models have been implemented into computer codes and have been successfully used to solve practical engineering problems particularly under monotonic loading conditions. Compared with the models for monotonic loadings, more improvements for cyclic models are necessary in order to obtain more accurate predictions for the dynamic behavior of geomaterials, e.g., the behavior during earthquakes. A cyclic elastoplastic model has been developed in this study for sandy soils; it is based on the kinematical hardening rule with a yield function that includes the changes in the stress ratio and the mean effective stress considering the degradation of the yield surface. From a simulation with the present model, it has been found that strong non-associativity leads to a large decrease in the mean effective stress during cyclic deformations under undrained conditions, while the model with the associated flow rule does not. This result is quite important because the mean effective stress becomes almost zero at the state of full liquefaction. Compared with the experimental results, the model can accurately reproduce the cyclic behavior of soil.

Hysteretic Performance Analysis of Self-Centering Buckling Restrained Braces Using a Rheological Model

AbstractIn this paper, a cyclic elastoplastic model applicable for studying the hysteretic performance of self-centering buckling restrained braces (SC-BRBs) is established based on the rheological analysis method. The linear-elastic pretensioned rods and superelastic shape memory alloy (SMA) pretensioned rods can be taken into account, and the tube stiffness modification coefficient in consideration of fabrication tolerances is introduced in this model. In the proposed rheological model simulating the SC-BRB specimens, the prediction of the hysteretic performance accurately matched the experiments. The proposed rheological model was applied to study the influence of the key structural parameters on the SC-BRB hysteretic performance: the energy dissipation of SC-BRBs with SMA pretensioned rods is superior to that of linear-elastic pretensioned rods; an increase of pretension and the area of the pretensioned rods will have different impacts on the hysteretic performance of SC-BRBs with linear-elastic prete...

H-adaptivity applied to liquefiable soil in nonlinear analysis of soil–pile interaction

This paper is concerned with application of the h-adaptive finite element method to dynamic analysis of a pile in liquefiable soil considering large deformation. In finite element analysis of pile behavior in liquefiable soil during an earthquake, especially considering large deformation of liquefied ground, error due to discretization in the zone near the pile becomes very large. Our purpose was to refine the approximation of the finite element method. The updated Lagrangian formulation and a cyclic elasto-plastic model based on the kinematic hardening rule were adopted to deal with the nonlinearity of the soil. The mixed finite element and finite difference methods together with the u- p formulation and Biot's two-phase mixture theory were used. To improve the accuracy and increase the efficiency of finite element analysis, an h-adaptive scheme that included a posteriori error estimation and h-version mesh refinement was applied to the analysis. The calculated results of effective stress were smoothed locally by the extrapolation method and smoothed stress was used to calculate the L 2 norm of the effective stress error in the last step of the calculation of each time increment. The mesh was refined by a fission procedure based on the indication of the error estimate As a numerical example, a soil–pile interaction system loaded cyclically was analyzed by our method.

Adaptive Mesh Refinement and Error Estimate for 3-D Seismic Analysis of Liquefiable Soil Considering Large Deformation

Such soil structures as river dikes, high way embankments and earth dams frequently have been damaged during major earth- quakes, often due to liquefaction of embankments and foundation soils. In most cases, unacceptable, large, permanent deformation has occurred due to liquefaction of the supporting, loose, cohesion- less foundation soil. The seismic design of soil structures in these liquefiable soils poses very difficult problems for analysis and design. The possibility of liquefaction necessitates further investi- gation not only experimentally but by numerical analysis. ABSTRACT The focus of this paper is on 3-D adaptive analysis method of liquefiable soil improvement of the approximate quality of nonlinear numerical simulation of the liquefaction process with large deformation. This adaptive tech- nique was applied to the 3-D non-linear FE analysis of liquefiable soil considering large deformation, including the liquefaction phenomenon. The cyclic elasto-plastic model and updated Lagrangian formulation were adopted in the three-dimensional FE analysis. The fission procedure belonging to the h-refinement indicated by the error estimator, a posteriori error estimate procedure depending on L 2 -norm of strain and superconvergent patch recov- ery method, was used. The convergence of this error estimate scheme and the effectiveness of h-adaptive mesh refinement were shown by simple examples. The adaptive FE method was applied to the three-dimensional prac- tical seismic analysis of an embankment constructed on liquefiable soil, and its efficacy demonstrated in detail. Application of the adaptive technique to the nonlinear analysis of saturated soil, including the liquefaction process, is a valuable step in the three-dimensional seismic analysis of liquefaction.