scholarly journals Multiscale Method for Seismic Response of Near-Source Sites

2020 ◽  
Vol 2020 ◽  
pp. 1-19
Author(s):  
Shutao Li ◽  
Jingbo Liu ◽  
Zhou Yang ◽  
Xin Bao ◽  
Fei Wang ◽  
...  
Keyword(s):  
Seismic Response ◽  
Seismic Wave ◽  
Free Field ◽  
Multiscale Method ◽  
Small Scale ◽  
Structure Model ◽  
Underground Structures ◽  
Artificial Boundary ◽  
Site Structure ◽  
Source Site

The traditional source-site-structure model for the calculation of seismic response of underground structures at near-source sites is restricted by the grid scale and the size of the structure. As a result, an excessive number of elements in the model make the numerical solving process difficult. To solve problems such as an inefficient computation and challenging nonlinear simulation, a multiscale analysis method for the calculation of the seismic response of underground structures at near-source sites is developed. The generalized free-field seismic response of the near-source region is obtained by establishing a large-scale calculation model of the source site and is used to simulate the fracture mechanism of faults and the process of seismic wave propagation. Then, using the method of seismic wave input based on artificial boundary substructures, the free-field motion of the wave is transformed into the equivalent seismic load, which is the seismic wave input data for the small-scale region of interest. Finally, with the help of local elements with special shapes to realize the grid transition of different scales, a small-scale model with reasonable soil-underground structure interaction is established, and the seismic response of the overall model can be effectively solved. The calculation and analysis of the seismic response of underground structures in irregular terrain are carried out. Compared with the results obtained directly from the source-site-structure model, the multiscale method has satisfactory accuracy and meets the needs of engineering design. Since the number of elements is fewer and the calculation time is much shorter than those required by the traditional model, the advantages in computational efficiency of the new method are highlighted. In addition, the reflected waves are too weak to have a considerable impact on structures because of the great energy loss at the reflection interface, which further proves the feasibility of the closed artificial boundary substructure method.

Evaluation of Formation of Plastic Hinge and Seismic Behavior of Steel Structures Due to Soil–Structure–Tunnel Interaction

2020 ◽  
Vol 14 (03) ◽  
pp. 2050014
Author(s):  
Arash Rostami ◽  
Abdolreza S. Moghadam ◽  
Mahmood Hosseini ◽  
Nima Asghari
Keyword(s):  
Seismic Response ◽  
Land Surface ◽  
Plastic Hinge ◽  
Free Field ◽  
Steel Structures ◽  
Underground Structures ◽  
Effective Parameters ◽  
Plastic Hinges ◽  
Underground Cavities ◽  
Real Earthquake

The seismic design of the structures is carried out by technical regulations and codes in free-field conditions (regardless of underground cavities). With the availability of tunnels and the complex interaction between the tunnel and the aboveground structures, which may be contemplated wrongly, it could be dangerous for over ground buildings and structures. Consequently, the examination of the underground tunnels and their impact on the land surface and adjacent buildings seismic response seems to be significant. The present research focuses on formation of the plastic hinges in steel structures due to underground cavities and the soil–tunnel–structure interaction of underground structures. First, an existing model was verified by finite element method and the results were compared with a sample specimen. Thus, several effective parameters were considered and studied such as soil type, multi-story structures (4, 8 and 12 stories) and dynamic load type. Then the models were evaluated under real earthquake records. As a result, the seismic response of the structures and plastic conditions of plastic hinge conditions were obtained. The results indicate that the underground cavities have affected the formation of plastic hinges in the structure. They increased the input energy to the structure and had an impact on the total behavior of the structures. Also, the high-rise structures were much more vulnerable to underground tunnels. Therefore, the structures which are located above the underground cavities should be retrofitted and rehabilitated.

scholarly journals On the Characteristics of Ground Motion and the Improvement of the Input Mode of Complex Layered Sites

2020 ◽  
Vol 6 (5) ◽  
pp. 848-859
Author(s):  
Hongke Pan ◽  
Xinxin Jiang
Keyword(s):  
Seismic Response ◽  
Seismic Wave ◽  
Homogeneous Model ◽  
Artificial Boundary ◽  
Engineering Structure ◽  
Input Method ◽  
Input Mode ◽  
Propagation Law ◽  
Boundary Model ◽  
Equivalent Load

It is a hot research topic to perform the dynamic interaction analysis between the engineering structure and the soil by using the time-domain method. This paper studies the seismic behaviour of the layered sites and the seismic response of the structures using the viscous-spring artificial boundary theory. The artificial boundary model of viscous-spring is initially based on homogeneous foundation. For the layered site (Foundation), the traditional homogeneous model or equivalent load input mode is not suitable, which may bring great error. By introducing the changes of coefficients and phases of reflection and transmission of seismic waves at the interface between layers, an improved method of equivalent load input mode of traditional viscous-spring artificial boundary model is proposed. This new wave model can simulate the propagation law of seismic wave in layered site more accurately, which is available for the seismic performance of engineering structure under the condition of large and complex layered site. At last, the simplified homogeneous model, the equivalent load input method and the improved layered model input method are used to study the seismic response of the engineering example. It is shown that the results calculated by the three methods are different, which shows that the homogeneous foundation model and the conventional equivalent load input method of seismic wave cannot simulate the seismic force accurately, whereas the improved wave input model can better reflect the characteristic of traveling wave in layered sites.

Seismic Response of Slab Culvert in Loess Region

2012 ◽  
Vol 204-208 ◽  
pp. 2461-2464 ◽  
Author(s):  
Hai Bo Wang ◽  
Yu Tao Pan ◽  
Jun Min Shen ◽  
Jun Jie Zheng
Keyword(s):  
Numerical Analysis ◽  
Seismic Response ◽  
Seismic Wave ◽  
Incident Angle ◽  
Numerical Results ◽  
Dynamic Loads ◽  
Active Area ◽  
Underground Structures ◽  
Earthquake Resistant ◽  
Loess Region

Buried culverts are usually considered to be earthquake-resistant underground structures. Therefore, few studies have been conducted to investigate the seismic response of slab culverts under high fill embankment which are usually subjected to extreme dynamic loads. This paper presents a numerical analysis of the seismic response of slab culvert under high fill embankment in a loess region which is also a seismically active area in China. The influence of important factors such as fill height, incident angle of seismic wave and magnitude of earthquake on the response of culvert is carefully examined. And possible failures of culverts are also analyzed according to the numerical results.

scholarly journals An Arc-consistent Viscous-spring Artificial Boundary for Numerical Analysis of the Seismic Response of Underground Structures

2021 ◽  
Author(s):  
Dan Ye ◽  
Shangzhi Yin ◽  
Dengzhou Quan
Keyword(s):  
Numerical Analysis ◽  
Seismic Response ◽  
Shaking Table Test ◽  
Near Field ◽  
Shaking Table ◽  
Test Results ◽  
Underground Structures ◽  
Artificial Boundary ◽  
Finite Element Software ◽  
Artificial Boundaries

Abstract A new arc consistent viscous-spring artificial boundary (ACVAB) was proposed by changing a traditional flat artificial boundary based on the theory of viscous-spring artificial boundaries. Through examples, the concept underpinning the establishment, and specific setting of, the boundary in the finite element software were described. Through comparison with other commonly used artificial boundaries in an example for near-field wave analysis using the two-dimensional (2-d) half-space model, the reliability of the ACVAB was verified. Furthermore, the ACVAB was used in the numerical analysis of the effects of an earthquake of underground structures. The results were compared with shaking-table test results on underground structures. On this basis, the applicability of the ACVAB to a numerical model of the seismic response of underground structures was evaluated. The results show that the boundary is superior to common viscous-spring boundaries in terms of accuracy and stability, and therefore it can be used to evaluate radiation damping effects of seismic response of underground structures and is easier to use.

3D Valley Site Effect on the Nonlinear Seismic Response of Earth Dam

2013 ◽  
Vol 353-356 ◽  
pp. 1806-1810
Author(s):  
Yong Qiang Li ◽  
Li Ping Jing ◽  
Hai An Liang ◽  
Yan Zou ◽  
Wei Feng Sun
Keyword(s):  
Seismic Response ◽  
Damping Ratio ◽  
Free Field ◽  
Site Effect ◽  
Earth Dam ◽  
Dynamic Strain ◽  
Triaxial Tests ◽  
Artificial Boundary ◽  
Nonlinear Seismic Response ◽  
Valley Site

A three dimensional numerical model for a typical earth dam and its valley site was established and the nonlinear seismic response of this model was performed. Experimental data of cyclic triaxial tests were adopted to determine the curves of modulus ratio and damping ratio that vary with dynamic strain amplitude. Free-field artificial boundary and viscous artificial boundary were employed and the input waves were the revised ground motions obtained from the station near the dam. Distributions of the PGA, displacement, residual deformation, shear strain increment and element failure state were presented. Results demonstrate that the 3D local valley site effect has a significant influence on the seismic response of earth dam.

scholarly journals An Arc-Consistent Viscous-Spring Artificial Boundary for Numerical Analysis of Seismic Response of Underground Structures

2022 ◽  
Vol 2022 ◽  
pp. 1-12
Author(s):  
Dan Ye ◽  
Shangzhi Yin ◽  
Yihong Wang ◽  
Taian Zuo
Keyword(s):  
Numerical Analysis ◽  
Seismic Response ◽  
Shaking Table Test ◽  
Near Field ◽  
Shaking Table ◽  
Test Results ◽  
Underground Structures ◽  
Artificial Boundary ◽  
Finite Element Software ◽  
Artificial Boundaries

A new arc-consistent viscous-spring artificial boundary (ACVAB) was proposed by changing a traditional flat artificial boundary based on the theory of viscous-spring artificial boundaries. Through examples, the concept underpinning the establishment and specific setting of the boundary in the finite element software were described. Through comparison with other commonly used artificial boundaries in an example for near-field wave analysis using the two-dimensional (2D) half-space model, the reliability of the ACVAB was verified. Furthermore, the ACVAB was used in the numerical analysis of the effects of an earthquake on underground structures. The results were compared with the shaking table test results on underground structures. On this basis, the applicability of the ACVAB to a numerical model of seismic response of underground structures was evaluated. The results show that the boundary is superior to common viscous-spring boundaries in terms of accuracy and stability, and therefore, it can be used to evaluate radiation damping effects of seismic response of underground structures and is easier to use.

scholarly journals Experimental and analytical study of seismic site response of discontinuous permafrost

2016 ◽  
Vol 53 (9) ◽  
pp. 1363-1375 ◽  
Author(s):  
Behrang Dadfar ◽  
M. Hesham El Naggar ◽  
Miroslav Nastev
Keyword(s):  
Shear Wave ◽  
Site Response ◽  
Free Field ◽  
Frozen Soil ◽  
Shaking Table ◽  
Experimental Program ◽  
Small Scale ◽  
Seismic Site Response ◽  
Discontinuous Permafrost ◽  
Spectral Accelerations

Seismic site response of discontinuous permafrost is discussed. The presence of frozen ground in soil deposits can significantly affect their dynamic response due to stiffer conditions characterized by higher shear-wave velocities compared to unfrozen soils. Both experimental and numerical investigations were conducted to examine the problem. The experimental program included a series of 1g shaking table tests on small-scale models. Nonlinear numerical analyses were performed employing FLAC software. The numerical model was verified using the obtained experimental results. Parametric simulations were then conducted using the verified model to study variations of the free-field spectral accelerations (on top of the frozen and unfrozen soil blocks) with the scheme of frozen–unfrozen soil, and to determine the key parameters and their effects on seismic site response. Results show that spectral accelerations were generally higher in frozen soils than in unfrozen ones. It was found that the shear-wave velocity of the frozen soil as well as the assumed geometry of the blocks and their spacing have a significant impact on the site response.

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.

Sensitivity analysis of geotechnical site conditions effect on the seismic response of a saturated inhomogeneous poroviscoelastic soil profile

2018 ◽  
Vol 15 (6) ◽  
pp. 661-677 ◽  
Author(s):  
Toufiq Ouzandja ◽  
Mohamed Hadid
Keyword(s):  
Soil Properties ◽  
Seismic Response ◽  
Pore Water ◽  
Soil Profile ◽  
Water Saturation ◽  
Free Field ◽  
Response Spectra ◽  
Response Analysis ◽  
Content Type ◽  
Linear And Nonlinear

Purpose This paper aims to present the investigation of the linear and nonlinear seismic site response of a saturated inhomogeneous poroviscoelastic soil profile for different soil properties, such as pore-water saturation, non-cohesive fines content FC, permeability k, porosity n and coefficient of uniformity Cu. Design/methodology/approach The inhomogeneous soil profile is idealized as a multi-layered saturated poroviscoelastic medium and is characterized by the Biot’s theory, with a shear modulus varying continuously with depth according to the Wichtmann’s model. Seismic response analysis has been evaluated through a computational model, which is based on the exact stiffness matrix method formulated in the frequency domain assuming that the incoming seismic waves consist of inclined P-SV waves. Findings Unlike the horizontal seismic response, the results indicate that the vertical one is strongly affected by the pore water saturation. Moreover, in the case of fully saturated soil profile, the same vertical response spectra are found for the two cases of soil behavior, linear and nonlinear. Originality/value This research is a detailed study of the geotechnical soil properties effect on the bi-directional seismic response of saturated inhomogeneous poroviscoelastic soil profile, which has not been treated before; the results are presented in terms of the peak acceleration ratio, as well as the free-field response spectra and the spectral ratio (V/H).

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