scholarly journals EVALUATION OF UNDERGROUND STRUCTURES SUBJECTED TO SEISMIC LOADS

2019 ◽  
Vol 23 ◽  
pp. 38-43
Author(s):  
Jan Pruška
Keyword(s):  
Soil Structure ◽  
Free Field ◽  
Fem Analysis ◽  
Field Analysis ◽  
Seismic Loads ◽  
Dynamic Effects ◽  
Underground Structures ◽  
Arbitrary Geometry ◽  
Fem Model ◽  
Fem Method

The paper is focused on the evaluation of the effect of earthquakes on underground structures. Free-field analysis is one solution of this task common mainly in engineering tunnelling practice, but it has some rather simplified aspects (e.g. equivalent shear strain is constant). Pseudostatic finite element calculation combines free-field analysis and the advantages of a FEM model. Dynamic effects are introduced in the form of displacements prescribed along the vertical boundaries of the FEM model in a usually static manner. This approach also implies constant material parameters for the geological profile in the horizontal direction, an arbitrary geometry of excavation, soil structure interaction and description of share waves as a time-dependent 1D analysis of the so called free-field column. Moreover, there is shown an example comparing pseudo-static FEM analysis with an analytical method. Finally, the advantages of the pseudo-static FEM method are presented.

scholarly journals Modification Research of the Internal Substructure Method for Seismic Wave Input in Deep Underground Structure-Soil Systems

2019 ◽  
Vol 2019 ◽  
pp. 1-13 ◽  
Author(s):  
Xin Bao ◽  
Jingbo Liu ◽  
Dongyang Wang ◽  
Shutao Li ◽  
Fei Wang ◽  
...  
Keyword(s):  
Free Surface ◽  
Seismic Wave ◽  
Soil Structure ◽  
Underground Structure ◽  
Computational Effort ◽  
Seismic Loads ◽  
Underground Structures ◽  
Computational Accuracy ◽  
Substructure Method ◽  
Deep Underground

A new internal substructure method for seismic wave input in soil-structure systems was recently proposed. This method simplifies the calculation of equivalent input seismic loads and avoids the participation of artificial boundaries in the process of seismic wave input. However, in previous research and applications, the internal substructures are usually intercepted down from the free surface, which forms large substructures and increases the computational effort for data management on the substructure nodes, especially for deep underground structures. In this study, the internal substructure method is modified by intercepting the internal substructures entirely beneath the free surface and adjacently around the underground structures. Then, the equivalent input seismic loads are obtained through the dynamic analysis of the internal substructures and applied to the corresponding positions of the total soil-structure models. Thus, the earthquake energy can be more efficiently input into the region near the underground structures without losing computational accuracy. We provide the detailed implementation procedures of this modified method and validate its applicability and accuracy through the scattered problems of underground cavities in homogeneous and layered half-space sites.

scholarly journals Influence of Water-Structure and Soil-Structure Interaction on Seismic Performance of Sea-Crossing Continuous Girder Bridge

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Jie Guo ◽  
Kunpeng Wang ◽  
Hongtao Liu ◽  
Nan Zhang
Keyword(s):  
Soil Structure ◽  
Hydrodynamic Force ◽  
Free Field ◽  
Water Structure ◽  
Field Analysis ◽  
Soil Structure Interaction ◽  
Structure Interaction ◽  
Bridge Model ◽  
Continuous Girder Bridge ◽  
Girder Bridge

Based on the Hong Kong-Zhuhai-Macao project, considering the fluid-structure interaction and soil-structure interaction, the seismic response of a sea-crossing continuous girder bridge is analyzed. Three-dimensional nonlinear numerical bridge model is developed, in which the hydrodynamic force is represented by added mass and pile-soil interaction is represented by p-y elements. Meanwhile, stratification of soil is considered in the free field analysis. Through the comparison of responses of the bridge cases, the effects of earthquake-induced hydrodynamic force and pile-soil interaction are studied. For the influence of hydrodynamic force, the results show that it is relatively slight as compared with pile-soil interaction; moreover pile foundation is more sensitive to it than other bridge components. The influence of pile-soil interaction is relatively significant. When both of the interactions are considered, the influence is not a simple superposition of acting alone, so it is recommended to consider both factors in dynamic analysis.

Simple approach to obtain ground amplification motion of surface soil deposits with a radical change of depth

2005 ◽  
Vol 42 (2) ◽  
pp. 491-498
Author(s):  
Dae-Sang Kim ◽  
Kazuo Konagai
Keyword(s):  
Seismic Design ◽  
Surface Soil ◽  
Underground Structure ◽  
Free Field ◽  
Alluvial Soil ◽  
Radical Change ◽  
Simple Approach ◽  
Clear Understanding ◽  
Underground Structures ◽  
Soil Deposits

Earthquake observations at different sites within alluvial soil deposits have demonstrated that the motion of buried underground structures closely follows that of the surrounding soil. Therefore, it is usual in a seismic design process to apply free-field ground displacements through Winkler-type soil springs to an underground structure to evaluate stress patterns induced within its structural members. Using a simplified approach, this paper provides a clear understanding of resonant horizontal ground displacement of and strain in a surface soil deposit with a radical change of depth and of where they occur.Key words: simple approach, seismic design, earthquake, resonance, underground structures.

Analysis of Cogging Torque of PM Motor with Radial Magnetic Field and Parallel Magnetic Field

2011 ◽  
Vol 105-107 ◽  
pp. 2289-2294
Author(s):  
Jun Qiang Lian ◽  
Shun Yi Xie ◽  
Jian Wang
Keyword(s):  
Magnetic Field ◽  
Air Gap ◽  
Analytic Method ◽  
Analytic Model ◽  
Parallel Magnetic Field ◽  
Radial Magnetic Field ◽  
Fem Model ◽  
Cogging Torque ◽  
Fem Method

This paper provide two methods to analyze the cogging torque of PM motor with radial magnetic field and parallel magnetic field, FEM method and Analytic method. The FEM model and Analytic model of PM motor with radial magnetic field and parallel magnetic field are founded. We analyze the model in both methods. From the result of analysis. The air-gap magnetic density of PM motor can be analyzed. We can find the cogging torque of radial magnetic field PM motor is much heavily than the cogging torque of parallel magnetic field PM motor. The result of Analytic method is close to the result of FEM method. The Analytic method is useful in analyze the cogging torque of PM motor.

A new approach for displacement and stress monitoring of tunnel based on iFEM methodology

2021 ◽  
Author(s):  
Pierclaudio Savino ◽  
Francesco Tondolo
Keyword(s):  
Input Data ◽  
Structural Response ◽  
Fem Analysis ◽  
Computational Procedure ◽  
Loading Conditions ◽  
Underground Structures ◽  
Stress Monitoring ◽  
Load Pattern ◽  
Structural Configurations ◽  
Structural Loading

Abstract Structural monitoring plays a key role for underground structures such as tunnels. Strain readings are expected to report structural conditions during construction and at the final delivery of the works. Furthermore, it is increasingly requested an extension to long-term monitoring from contractors with possible use of the same system in service during construction. A robust and efficient monitoring methodology from discrete strain measurements is the inverse Finite Element Method (iFEM), which allows to reconstruct the structural response without input data on the load pattern applied to the structure as well as material and inertial properties of the elements and therefore it is interesting for structural configurations affected by uncertain loading conditions, such as the tunnel. The formulation presented in this paper, based on the iFEM theory, is improved from the previous work available in literature for both the shape functions used and the computational procedure. Indeed, the approach allows to overcome inconsistencies related to structural loading conditions and a pseudo-inverse matrix preserve all the rigid body modes without imposing specific constraints which is typical for tunnels. Numerical validation of the iFEM procedure is performed by simulating the input data coming from a tunnel working in a heterogeneous soil under different loading conditions with direct FEM analysis.

Vertical soil-structure interaction effects

1979 ◽  
Vol 69 (1) ◽  
pp. 221-236
Author(s):  
R. R. Little ◽  
D. D. Raftopoulos
Keyword(s):  
Nuclear Power ◽  
Soil Structure ◽  
Power Plants ◽  
Structural Model ◽  
Free Field ◽  
Interaction Effects ◽  
Soil Structure Interaction ◽  
Response Curves ◽  
Transformation Techniques ◽  
Structure Interaction

abstract An analytical expression describing the three-dimensional vertical soil-structure interaction effects is developed using Laplace and Hankel transformation techniques. Utilizing these transformation techniques and normal mode theory of vibration, an N-mass structural model is coupled to an elastic half-space representing the earth. The resulting interaction equation is solved by numerical iteration techniques for a model of a nuclear power plant subjected to actual earthquake ground excitation. The effects of the soil-structure interaction are evaluated by comparing free-field acceleration spectrum response curves with similar curves determined from the foundation motion. These effects are found to be significant for structures typical of modern nuclear power plants subjected to seismic ground motions.

scholarly journals Effect of Soil Classification on Seismic Behavior of SMFs considering Soil-Structure Interaction and Near-Field Earthquakes

2018 ◽  
Vol 2018 ◽  
pp. 1-17 ◽  
Author(s):  
Shahrokh Shahbazi ◽  
Iman Mansouri ◽  
Jong Wan Hu ◽  
Armin Karami
Keyword(s):  
Soil Structure ◽  
Near Field ◽  
Free Field ◽  
Soil Structure Interaction ◽  
Nonlinear Time History Analysis ◽  
Type Ii ◽  
Steel Buildings ◽  
Moment Frames ◽  
Structure Interaction ◽  
Soil Flexibility

Seismic response of a structure is affected by its dynamic properties and soil flexibility does not have an impact on it when the bottom soil of foundation is supposedly frigid, and the soil flexibility is also ignored. Hence, utilizing the results obtained through fixed-base buildings can lead to having an insecure design. Being close to the source of an earthquake production causes the majority of earthquake’s energy to reach the structure as a long-period pulse. Therefore, near-field earthquakes produce many seismic needs so that they force the structure to dissipate output energy by relatively large displacements. Hence, in this paper, the seismic response of 5- and 8-story steel buildings equipped with special moment frames (SMFs) which have been designed based on type-II and III soils (according to the seismic code of Iran-Standard 2800) has been studied. The effects of soil-structure interaction and modeling of the panel zone were considered in all of the two structures. In order to model radiation damping and prevent the reflection of outward propagating dilatational and shear waves back into the model, the vertical and horizontal Lysmer–Kuhlemeyer dashpots as seen in the figures are adopted in the free-field boundary of soil. The selected near- and far-field records were used in the nonlinear time-history analysis, and structure response was compared in both states. The results obtained from the analysis showed that the values for the shear force, displacement, column axial force, and column moment force on type-III soil are greater than the corresponding values on type-II soil; however, it cannot be discussed for drift in general.

scholarly journals UNCONVENTIONAL MATERIAL PART FEM ANALYSIS

2016 ◽  
Vol 2 (1) ◽  
pp. 20-25
Author(s):  
Michal Tropp ◽  
Michal Lukac
Keyword(s):  
3D Model ◽  
Fem Analysis ◽  
Carbon Composite ◽  
Von Mises Stress ◽  
Composite Component ◽  
Fem Model ◽  
Material Part ◽  
Alternative Materials ◽  
Von Mises ◽  
Ansys Workbench

The article covers the usability of alternative materials in vehicle construction. The paper elaborates upon the setup of the process and analysis of the results of the carbon composite component FEM model. The 3D model, used for the examination, is a part of axle from an alternative small electric vehicle. The analysis was conducted with the help of MSC Adams and Ansys Workbench software. Color maps of von Mises stress in material and total deformations of the component are the results of calculation.

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