Parameters affecting laterally loaded piles in frozen soils by an efficient sensitivity analysis method

- Adapt the direct differentiation method for sensitivity analysis of a frozen silt-pile interaction system
- Study material parameters critical to lateral response of piles embedded in frozen ground
- Rank the relative importance of material parameters on system responses at varying lateral deflections
- Quantify the impact of a parameter on a system response

In cold regions, accurately simulating the nonlinear responses of frozen soil-structure interaction (SSI) systems is of significant importance for the seismic safety assessment. This paper presents a finite element (FE) simulation of nonlinear lateral responses of a real reinforced-concrete filled steel pipe pile embedded in frozen ground at an outdoor test site in Fairbanks, Alaska. A pressure-independent multi-yield surface J2 plasticity model is used to simulate the frozen soil behavior, while frame element with fiber section and nonlinear steel/concrete model are used for the pile. The FE analysis results agree well with the experiment results. Furthermore, the response sensitivities to various material parameters are computed by using an efficient and accurate gradient computation method, i.e., direct differentiation method (DDM), with limited additional computational cost. Based on DDM, the relative importance of material parameters on system responses is studied when the system is subjected to varying lateral deflections, respectively (corresponding to different levels of lateral loads such as earthquakes). Stiffness-related parameters are dominant when the system is subject to small deflections, while strength-related or post-yield parameters become dominant for large deflections. In addition, global responses are slightly more sensitive to material parameters of pile than the parameters of frozen soil. The response sensitivity to the unfrozen soil below the frozen ground crust is almost negligible. Finally, the response sensitivities to the soil parameters are observed to decrease when the distance of the soil from the pile increases. The sensitivity analysis methodology presented in this paper can be adapted to other frozen soil-pile interaction cases and the study results provide valuable insight for engineering practice.