Dynamic Interaction of Soil-Isolated Structure:A Systematic Review

Isolation technique of ground structure is a hot topic in the field of earthquake engineering and structure dynamics.Since soil-isolated structure dynamic interaction study is of great significance to enhance seismic performance of isolated structures and revision of relevant isolation specifications,research on dynamic interaction of soil-isolated structure has attracted more and more attention.Based on the basic theory of soil-structure dynamic interaction,we summarize and analyze the research status quo of soil-isolated structure dynamic interaction by means of theoretical analysis,numerical simulation,model test,prototype observation and seismic performance.After reviewing the results of previous research,we reveal that some key issues,which can be used to uncover dynamic interaction mechanism and seismic response characteristics of soil-isolated structures interaction system,should not be neglected.Based on the concept of seismic performance design and the latest research of soil-isolated structure dynamic interaction,we predict the future development of soil-isolated structure dynamic interaction by elastoplastic time history analysis method,seismic performance level and practical analysis method based on energy.

Improved Simulation Method for Soil-Geogrid Interaction of Reinforced Earth Structure in FEM

The interaction between geogrid and soil is crucial for the stability of geogrid-reinforced earth structure. In finite element （FE） analysis, geogrids are usually assumed as beam or truss elements, and the interaction between geogrid and soil is considered as Coulomb friction resistance, which cannot reflect the true stress and displacement developed in the reinlbrcement. And the traditional Lagrangian elements used to simulate soil always become highly distorted and lose accuracy in high-stress blocks. An improved geogrid model that can produce shear resistance and passive resistance and a soil model using the Eulerian technique, in combination with the coupled Eulerian-Lagrangian （CEL） method, are used to analyze the interaction between geogrid and soil of reinforced foundation test in ABAQUS. The stress in the backfill, resistance of geogrid, and settlement of foundation were computed and the results of analysis agree well with the experimental results. This simulation method is of referential value for FE analysis of reinforced earth structure.

DYNAMIC FINITE LAYER-ELEMENT ANALYSIS OF SOIL-STRUOTURE INTERACTION FOR NEW-TYPE OFFSHORE PLATFORM

In this paper, a new method called dynamic finite layer--element method (DFLEM) is used to analyse the soil--structure interaction of new type offshore platforms. Some valuable results have been obtained. The results show that the DFLEM is a new effective method to analyse dynamic soil--structure interaction and can be applied widely in practice.

Comparative analysis of seismic response characteristics of pile-supported structure

In order to analyze the seismic response characteristics of pile-supported structure,a computational model considering pile-soil-structure interaction effect was established by finite element method.Then,numerical implementation was made in time domain.At the same time,a simplified approximation for seismic response analysis of pile-soil-structure system was briefly presented.Furthermore,comparative study was performed for an engineering example.Through comparative analysis,it is shown that the results obtained by the simplified method well agree with those achieved by the finite element method.These results show that spectrum characteristics and intensity of input earthquakes are two important factors that can notablely influence the seismic response characteristics of superstructure.When the input ground motion acceleration amplitude gradually increases from 1 to 4 m/s2,the acceleration of pier top will increase,but it will not be simply proportional to the increase of input acceleration amplitude.

整体式桥台斜交梁桥地震反应研究

土-结构的相互作用对整体式桥台斜交桥梁的影响较大,目前缺乏相应的抗震研究。为了研究考虑土-结构相互作用的整体式斜交梁桥双向地震作用下的反应,采用ABAQUS数值软件,建立了考虑地基土和台后土在内的桥梁三维整体有限元计算模型,比较了三条不同频率地震波作用下动力时程分析的计算结果,并与采用p-y曲线建立的简化桩土模型计算结果进行对比。结果表明,在多遇地震下二者计算结果较为符合,在强震下计算结果有较大差距,采用整体精细模型能够反映土的非线性性能。由于桥台处与桥梁固结,斜交桥钝角处桥台应力较大,接近锐角处的2倍,台后钝角处的翼墙侧向压力增大,钝角处的桥台应考虑适当加强;强震下台后土和桥台可能出现脱离,台后土的非线性效应明显。

Progressive failure processes of reinforced slopes based on general particle dynamic method

In order to resolve grid distortions in finite element method(FEM), the meshless numerical method which is called general particle dynamics(GPD) was presented to simulate the large deformation and failure of geomaterials. The Mohr-Coulomb strength criterion was implemented into the code to describe the elasto-brittle behaviours of geomaterials while the solid-structure(reinforcing pile) interaction was simulated as an elasto-brittle material. The Weibull statistical approach was applied to describing the heterogeneity of geomaterials. As an application of general particle dynamics to slopes, the interaction between the slopes and the reinforcing pile was modelled. The contact between the geomaterials and the reinforcing pile was modelled by using the coupling condition associated with a Lennard-Jones repulsive force. The safety factor, corresponding to the minimum shear strength reduction factor "R", was obtained, and the slip surface of the slope was determined. The numerical results are in good agreement with those obtained from limit equilibrium method and finite element method. It indicates that the proposed geomaterial-structure interaction algorithm works well in the GPD framework.

Simplified Damage Assessment of Slab Against External Blast Load

Recently, the mode approximation method(MAM) has been adopted to analyze beam elements against blast load. However, in real cases, the main structural element of an underground structure is slab and side wall since they not only support the structure itself but also may sustain external loads from blast, earthquake, and other kinds of impact. In the present study, the MAM is extended from beam to plate elements and the soil-structure interaction is considered and simplified when calculating structural response under blast load. Pressure-impulse diagrams are generated accordingly for further quick damage assessment.

Numerical Analysis of a Gravity Substructure for 5 MW Offshore Wind Turbines Due to Soil Conditions

In order to increase the gross generation of wind turbines, the size of a tower and a rotor-nacelle becomes larger. In other words, the substructure for offshore wind turbines is strongly influenced by the effect of wave forces as the size of substructure increases. In addition, since a large offshore wind turbine has a heavy dead load, the reaction forces on the substructure become severe, thus very firm foundations should be required. Therefore, the dynamic soil-structure interaction has to be fully considered and the wave forces acting on substructure accurately calculated. In the present study, ANSYS AQWA is used to evaluate the wave forces. Moreover, the substructure method is applied to evaluate the effect of soil-structure interaction. Using the wave forces and the stiffness and damping matrices obtained from this study, the structural analysis of the gravity substructure is carried out through ANSYS mechanical. The structural behaviors of the strength and deformation are evaluated to investigate an ultimate structural safety and serviceability of gravity substructure for various soil conditions. Also, the modal analysis is carried out to investigate the resonance between the wind turbine and the gravity substructure.