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Geostatic stress field procedure is the first and the most important step for the numerical simulation of geotechnical engineering, which greatly influences the simulation results. Traditional methods often fail when the model is complex. In this paper, based on finite element method (FEM) software ABAQUS, failure reasons of four commonly used methods for the geostatic stress field are studied. According to the analysis results, a new set of methods, which can provide reasonable displacement and stress field results under complex conditions, is proposed. The proposed methods follow the principle that the stress of different materials should be obtained separately to avoid stress distortion. Then, the accuracy and applicability of the proposed method are verified through a comparison study and a specific application. This study provides a theoretical basis for the method of geostatic stress field procedure under complex condition and can serve as a reference for relevant studies. [ABSTRACT FROM AUTHOR]

This paper reports an investigation into the impact resistance of concrete-encased concrete-filled steel tube (CFST) members with circular sections. A finite element analysis (FEA) model was established to simulate the impact behaviour of concrete-encased CFST under laterally low velocity impact, in which the strain rate effects of steel and concrete, the element erosion criteria of concrete, the interactions between concrete and steel, as well as the combined effects of axial load and lateral impact, were considered. Experimental data on reinforced concrete (RC), CFST and concrete-encased CFST members under drop hammer impact were used to verify the accuracy of the FEA model and a generally reasonable agreement was achieved for all three types of structures. A full-range analysis of the behaviour of concrete-encased CFST members with circular sections was then carried out with the FEA model to investigate the impact behaviour and impact resistance of the composite structure. The failure modes, sectional moment development, stress and strain development, as well as the contact behaviour between different parts were analyzed to highlight the reasons behind the good impact resistance of the composite structure. A parametric study was finally conducted with the FEA model to investigate the major parameters that may influence the impact resistance of the concrete-encased CFST members. [ABSTRACT FROM AUTHOR]

In slope reliability analysis, "local averaging" of the statistical soil parameters on the slope slip surface is the main factor influencing the results of the analysis. In this study, we analyzed the curvilinear local averaging of a 2-D random field by equation derivation based on random field theory and statistical analysis. By assuming a circular slip surface, the variance reduction due to curvilinear local averaging was obtained as a function of geometric characteristics of the slip surface and variance at a "point" level, and a simple reliability analysis method for homogeneous natural slope was proposed. The proposed method contains three major steps: statistical analysis of soil parameters by site tests, determination of the limit state curve using a series of deterministic finite element analyses, and the calculation of slope failure probability by integrating the probability density function corresponding to the limit state curve. A comparative analysis shows that the proposed slope reliability analysis method based on a curvilinear local averaging of a 2-D random field is reliable and efficient. [ABSTRACT FROM AUTHOR]

• Drop hammer impact teston40concrete-encased CFST specimensis carried out; • Test shows outer RC has a shear failure mode while core CFST deforms flexurally; • Shear mechanism of encased membersunderimpact is analyzedthrough FEAmodelling; • CFST's highshear resistancecontributes totheencased member'good resilience. The performance of concrete-encased concrete-filled steel tube (concrete-encased CFST) subjected to low-velocity impact is investigated through experimental and numerical studies in this paper. A total of 40 concrete-encased CFST specimens, 20 square and 20 circular ones, are tested under a drop hammer apparatus. It shows that while the outer RC components have a shear-dominated failure mode, the core CFST deforms in a flexural pattern. The influence of tested parameters on the impact force and midspan deflection of the specimens is summarized. A finite element analysis (FEA) model is then established to investigate the shear mechanism of concrete-encased CFST under impact. A comparative study between a concrete-encased CFST member and an RC member shows that the core CFST component could effectively mitigate the shear failure of the outer RC section under impact due to its high shear resistance; meanwhile, the outer RC component could well protect the core CFST and reduce its flexural deformation. Such composite effects make the concrete-encased CFST a desirable impact-resisting structure. Subsequently, a parametric study on the impact velocity shows that the debonding between outer RC and core concrete can be more prominent for the impact with a relatively higher velocity, and the use of shear studs is suggested for members under such circumstances. [ABSTRACT FROM AUTHOR]

• Experimental study on 20 concrete-encased CFST box specimens under drop hammer impact. • Analysis of the measured failure modes, impact force and mid-span deflection. • Numerical study on the composite effects of RC and CFST components under impact. This paper presents an experimental and numerical study on the lateral impact behaviour of concrete-encased concrete-filled steel tubular (CFST) box beams and columns. A total of 20 specimens with test parameters including the impact energy, the boundary conditions and the axial load level, are tested under a drop hammer impact apparatus. The experimental results, namely the failure modes, the time-history of the impact force and mid-span deflection, as well as the whole impact process, are analysed. It shows that the specimens fail in a shear-flexural pattern under the impact. The major features of the impact force and mid-span deflection curves are summarised and analysed. The influence of test parameters on the impact behaviour of the specimens, namely the peak value of the impact force, the impact duration and the residual mid-span deflection, are also discussed. A finite element analysis (FEA) model is established to investigate the composite effects between the RC and CFST components. The analysis shows that the RC component is the major impact resistance component in the structure. The CFST components, on the other hand, is well protected by the RC component and do not experience severe damage. The composite effects make the structure safer under impact loading and easier to be restored after impact. [ABSTRACT FROM AUTHOR]