3D Seismic Response Research Articles

Large-scale 3D seismic response analysis considering soil liquefaction in an urban area using the supercomputer “Fugaku”

Large-scale 3D seismic response analysis considering soil liquefaction in an urban area using the supercomputer “Fugaku”

Seismic analysis of underground tunnels subjected to 3D oblique incident P and SV waves by 2.5D approach

This paper presents, for the first time, the consideration of three-dimensional (3D) oblique incident P and SV waves in calculating the 3D seismic response of a lined tunnel embedded in a half-space by the 2.5D finite/infinite element method (FIEM). Firstly, the applicability of the 2.5D FIEM for 3D seismic analysis is summarized. With the exact solutions obtained for the free field in the Appendix, the equivalent seismic forces are rationally computed for the near-field boundary, considering the horizontal and vertical excitations of the Chi-Chi Earthquake. By performing seismic analysis of the half space embedded with a tunnel using the 2.5D FIEM, the time-domain responses of the tunnel are obtained. The accuracy of the present solutions is verified against those of de Barros and Luco. Conclusions drawn from the parametric study include: (1) Stress concentration for the principal stress under oblique incident seismic waves occurs at the polar angles of 0° (vault), 90°, 180° (inverted arch), and 270° of the lining wall. (2) The vault and inverted arch are the weakest parts of the tunnel during earthquakes. (3) The accelerations of the tunnel during earthquakes can be regarded as of the rigid body type. (4) The responses of the tunnel lining caused by SV waves of an earthquake are much more critical than those by P waves. (5) For arbitrary seismic waves, the maximum longitudinal acceleration azmax is of the same order of magnitude as the maximum horizontal acceleration axmax.

A 2.5D Finite Element Method Combined with Zigzag-Paraxial Boundary for Long Tunnel under Obliquely Incident Seismic Wave

Seismic waves propagation with an oblique angle to the tunnel axis will cause asynchronous tunnel motions and have a significant effect on the axial response. A high-precision 2.5D finite element method is established in the frequency domain to simulate the 3D seismic response of the tunnel. This method avoids the disturbance caused by the truncation of the tunnel in the longitudinal direction. Meanwhile, a 2.5D zigzag-paraxial boundary is derived to further improve the calculation efficiency of the 2.5D finite element model. Moreover, by combining the 2.5D finite element method, 2.5D zigzag boundary condition and seismic motion input methods, an obliquely incident substructure method for plane seismic waves is built by converting the plane seismic wave into equivalent nodal forces. The proposed 2.5D finite element method is verified by comparing with a reference solution. Finally, the 2.5D finite element method is applied to study the seismic response of the long lined tunnel. Parameter analyses illustrate that the wave propagation effect to the tunnel axis has a non-negligible influence on the axil deformation of long tunnels.

Towards the Monitoring of Underground Caves Using Geomatics and Geophysical Techniques: 3D Analyses and Seismic Response

Analyses of climate change, due to its impact not only on the weather and the environment but also on human health and life, are one of the most important study activities made in recent years. There is relatively high confidence that glacial melt and heavy rainfall events will continue to increase. These climate-related events carry a microseismic signature that can guide monitoring activities. In the last decade, there have been growing applications of long-term continuous ambient seismic noise systems to monitor landslides and potentially unstable rock sites. This work reports some of the activities made during a project performed under the Department of Excellence on Climate Change (2018–2022), funded by the Italian Ministry for University and Research (MUR), in order to improve environmental seismic analyses. The selected test site is the Bossea Cave (NW Italy), where two seismic stations were installed. The goals were to use these stations to understand and study climate change events above the Bossea Cave, analyzing the data from a geophysical and geomatics point of view. Starting with UAV flights and photogrammetric processing to obtain a 3D model of the cave, both ambient seismic noise and microseismicity analyses highlighted an important effect of air temperature and precipitation on the seismic response of the monitored rock mass overlying the Bossea Cave. In particular, a clear effect on the ambient seismic noise spectral content and the peak frequency of the microseismic events driven by temperature and precipitation was found during the warmer monitoring months, with almost zero delays in the seismic response. This is a preliminary but important study, even if longer monitoring data and thermal modeling efforts are needed to fully understand this seasonal variation.

3D-Seismic Response Analysis of the Secondary Piping System in Building Under Bi-Directional Earthquake

The secondary piping systems running along the height of buildings are subjected to significant stresses and accelerations due to the earthquake. Extensive research on the seismic response of primary and secondary systems has been carried out in the past. State of the art review papers on the subjects summarizes those researches. Although the response of the secondary piping system running along with the height of the primary structure like the building has been studied before, the stresses and accelerations developed in the piping system developed due to the bi-directional earthquake are not widely studied. In this paper, a six storied building with a secondary system taken as a pipe running from 1st to 6th story on one side of the building is taken as an illustrative example. A 3-D model of the primary and secondary system is analyzed for bi-directional earthquakes. Considering the full interaction between the primary and secondary structures, the non- linear time history analysis is carried out in SAP 2000 to obtain different response quantities of interest for a PGA level 0.3g with the major to minor ground motion ratio taken as 1:2/3. Response quantities of interest include the maximum accelerations, maximum displacements, and maximum stresses developed at critical sections of the pipe. Also, the floor response spectra are obtained. Results of the numerical study indicate that significant accelerations and stresses are induced in the pipe for a PGA level of 0.3g; the absolute accelerations at the pipe supports vary significantly leading to the generation of large stresses in the pipe.

3D seismic response assessment of barrette piled high-rise building with comprehensive subsurface modelling

The increased popularity of using barrette piled foundations for high-rise buildings has brought about a need to fully comprehend how the complete integrated system of soil, piles and superstructure is simulated realistically by 3D non-linear finite element (FE) models responding to the seismic excitation in time-domain. Subtle details of physical and spatial 3D soil variation are modelled by the novel image processing technique allowing more realistic subsurface geotechnical modelling. The borehole data from the site-specific investigation have been considered to reduce the epistemic uncertainties in 3D FE soil models. Paper adapts this advanced subsurface modelling technique to 3D seismic response analysis to enable more accurate predictions of the geotechnical seismic design process by explaining how 3D varying subsurface boundaries are represented by viscous damping in 3D seismic interaction analysis. 3D FE simulations subjected to bilateral seismic excitation have been performed representing the free-field boundaries, material damping and the penalty frictional contact algorithm for the pile-soil interface. It tackles the important aspect of this practical problem by exploring the deformation and the acceleration responses of soil, piles and superstructure in terms of the linear and nonlinear analyses. Paper reveals that the seismic responses are markedly affected by bilateral seismic excitations, nonlinearity and 3D lithological soil variation.

3D seismic response characteristics of a pile-mat-founded AP1000 nuclear-island building considering nonlinear hysteretic behavior of soil

Given the increase of nuclear power plants, it has become unavoidable for the pile-supported nuclear-island buildings to be constructed on the coastal deposits potentially influenced by strong earthquakes. The coupling influences of the hysteresis nonlinearity of soil and the soil-pile-structure interaction (SPSI) have not yet been considered comprehensively in the seismic response analysis of the nuclear-island building, although it is a vital issue. On the basis of a newly-developed generalized non-Masing hysteretic constitutive model, a 3D integrated simulation method is proposed to evaluate the seismic responses of the pile-mat-founded nuclear-island building system subjected to multidirectional earthquake motions. This integrated method involves an explicit parallel algorithm framework, comprising the nuclear-island building modeling, the pile-mat foundation modeling, the inhomogeneous soil domain modeling, and the artificial boundary condition. The bedrock records of near-field, moderate-far field and far-field earthquake scenarios are assumed for determining the bedrock motions of the ultimate and operational safety earthquakes. For an actual pile-mat-founded AP1000 nuclear-island building, the simulation results show the complexity and significance of the coupling effect of the site, the tridirectional earthquake shaking, and the secondary nonlinearity of soil. Such a complex coupling effect significantly increases the seismic responses of the pile-mat-founded nuclear-island building. A notable finding is that the scenario earthquakes with abundant long period components may have more destructive potential to the pile-mat-founded nuclear-island buildings than the scenario earthquakes with characteristics of abundant short period components and shorter durations. The results provide insights into the seismic design of the pile-mat-founded nuclear-island buildings, which could guide the design and construction of such similar facilities in the high seismic intensity regions.

Effect of geomaterial variability on seismic response analyses of earthen dams

In a recently completed research study, two-dimensional (2D) and three-dimensional (3D) seismic response analyses were performed on a hydraulic fill earthen dam located in north Texas, USA. Analysis results obtained from both methods were compared to study and address the influence of geomaterial variability on the seismic response of heterogeneous earthen dams such as hydraulic fill dams. For evaluating the material variability within the dam, twenty-eight piezocone penetration soundings (CPTu) were conducted along the crest of the dam. These CPTu soundings, along with the available laboratory test results, were utilized to represent various scenarios that depict geomaterial variability within the dam for numerical modeling and seismic response analysis. In the first scenario, limited subsurface investigation information obtained from six CPTu soundings distributed along the dam crest was considered to develop the numerical models. In the second scenario, all the twenty-eight CPTu soundings were utilized to model the same dam using extensive site characterization test results. The first natural frequency, earthquake-induced crest accelerations, and shear stresses of the dam segments were computed from 2D and 3D numerical analyses for both scenarios of site characterization results. Results indicated that a 3D analysis might be more appropriate than a 2D analysis for studying the seismic response of a heterogeneous earthen dam, especially when extensive site characterization information is available to model the dam for numerical analyses. Overall, the findings of this study emphasize the impact of geomaterial variability on seismic response analyses of heterogeneous earthen dams and will enable engineers to assess the conditions that warrant a comprehensive 3D analysis.

Amplification Effect of Ground Motion in Offshore Meandering Sedimentary Valley

A sedimentary valley has a visible amplification effect on a seismic response, and the current 2D topographies cannot truthfully reflect the twists and turns of a large-scale river valley. Taking a sinusoidal curved valley site as a model, the dynamic finite element analysis method and the introduction of a viscoelastic artificial boundary were developed to study the 3D seismic response of the dimensional topographies in the homogeneous curved valley to vertical incident P, SV, and SH waves. The results showed that the bending sedimentary valley site earthquake presented significant features simultaneously, depending on the number of valley bends, the frequency of the excitations, the shear wave velocity of sedimentary soil, and the depth of the river valley. The surface displacement amplitudes of three-dimensional meandering sedimentary valleys are significantly different from those of sedimentary basins. The amplification area of the meandering valley is related to the angle between the valley axis and wave vibration direction, and the amplification effect is significant when the angle is small. The movement in the main direction showed a center focus, and the secondary y-direction displacement showed both a central focus and an edge effect. When the frequency of the incident wave was close to the natural vibration frequency in a specific direction, the movement in this direction significantly increased because of the resonance effect. The displacement amplitude of the surface was proportional to the depth of the river valley, and the surface displacement was presented in different forms based on the frequency of the excitations. The results provided some guidance for the earthquake resistance of the curved valley site.

Development of regional simulation of seismic ground‐motion and induced liquefaction enhanced by GPU computing

AbstractMuch research has been conducted for physics‐based ground‐motion simulation to reproduce seismic response of soil and structures precisely and to mitigate damages caused by earthquakes. We aimed at enabling physics‐based ground‐motion simulations of complex three‐dimensional (3D) models with multiple materials, such as a digital twin (high‐fidelity 3D model of the physical world that is constructed in cyberspace). To perform one case of such simulation requires high computational cost and it is necessary to perform a number of simulations for the estimation of parameters or consideration of the uncertainty of underground soil structure data. To overcome this problem, we proposed a fast simulation method using graphics processing unit computing that enables a simulation with small computational resources. We developed a finite‐element‐based method for large‐scale 3D seismic response analysis with small programming effort and high maintainability by using OpenACC, a directive‐based parallel programming model. A lower precision variable format was introduced to achieve further speeding up of the simulation. For an example usage of the developed method, we applied the developed method to soil liquefaction analysis and conducted two sets of simulations that compared the effect of countermeasures against soil liquefaction: grid‐form ground improvement to strengthen the earthquake resistance of existing houses and replacement of liquefiable backfill soil of river wharves for seismic reinforcement of the wharf structure. The developed method accelerates the simulation and enables us to quantitatively estimate the effect of countermeasures using the high‐fidelity 3D soil‐structure models on a small cluster of computers.

A 2.5D IBEM to investigate the 3D seismic response of 2D topographies in a multi-layered transversely isotropic half-space

A two and half dimensional (2.5D) indirect boundary element method (IBEM) is developed to study the three dimensional (3D) seismic response of two dimensional (2D) topographies in a multi-layered transversely isotropic (TI) half-space, under obliquely incident qP-, qSV- and SH-waves. Based on the single-layer integral representation, the scattered fields are constructed by applying fictitious moving load on the boundary line elements, and the load densities are determined from the corresponding boundary conditions. The total wave fields can be obtained by superposition of the scattered fields and free fields solved by dynamic stiffness method. With aid of the dynamic 2.5D moving Green's functions (Ba et al. 2017b), this method has the merit of revealing the complex 3D wave-field characteristics, and the calculation domain being restricted to the cross section of topographies without the need of complex 3D discretization. The present formulations are validated by comparison with the published results, and by taking a semi-circular canyon as well as a semi-circular hill topographies as examples, selected numerical simulations are performed in both the frequency and time domains. Results show that the dynamic response for the TI medium differs remarkably from those for the isotropic case, simultaneously depending on incident angle and frequency of excitations. The amplification effects of the hill become prominent with the increase of Eh/Ev, with the displacement amplification more remarkable inside the hill region compared to that of the exterior region.

Seismic Performance of Soil-Ash and Soil-Ash-Foundation System

In this study, a 3D seismic response of soil deposit, soil-ash deposit and soil-ash-foundation system was investigated. Homogeneous sand deposit of 80m × 9m × 20m was initially analyzed. A pond ash layer is on top of the sand deposit with varying thicknesses and the efficiency of the pond ash layer on the sand deposit was evaluated for its best suitability. The optimum sand-ash deposit overlain by a shallow foundation has been analysed under the excitation of the Nepal (Mw:7.8) and North East India earthquake (Mw:7.5). A seismic response analysis was performed using finite element software PLAXIS3D. The finite element model adopted for the present study has been validated using 1D nonlinear ground response analysis programs. e.g. DEEPSOIL and Cyclic1D. Results of the response analysis have been determined in terms of acceleration, displacement, excess pore pressure, and excess pore pressure ratio. It was observed that, the sand-pond ash-foundation system experienced liquefaction when excited under the Nepal earthquake motion whereas it is safe against the North East India earthquake.

3D seismic response of a 2D hill-valley staggered topography modeled by a 2.5D multi-domain IBEM

3D seismic response of a 2D hill-valley staggered topography modeled by a 2.5D multi-domain IBEM

3D Seismic Response Analysis of Shallow Foundation Resting on Sandy Soil

In the present study, an attempt has been made to study the response of a shallow foundation resting on medium dense sandy soil under seismic excitation. Numerical analysis of the soil-foundation system has been carried out using 3D finite element software OpenSeesPL. The effect of boundary conditions (shear beam and rigid box type) and the water table (0 m, 1 m and 2 m below the ground surface) on the response of soil-foundation system under seismic excitation have been analysed. The responses of the soil-foundation system are presented in the form of acceleration, displacement, excess pore pressure, excess pore pressure ratio and settlement variations at different locations in the soil domain. The results of the numerical analysis indicate that the peak acceleration, displacement, excess pore pressure and settlement values are found to be more in shear beam type boundary condition than that of a rigid box type boundary condition. Hence, rigid confinement and lower water table can reduce the liquefaction potential of the soil-foundation system under seismic excitation.

Three‐Dimensional Nonlinear Seismic Response of Immersed Tunnel in Horizontally Layered Site under Obliquely Incident SV Waves

A three‐dimensional (3D) detailed numerical model of an immersed tunnel in a horizontally layered site is established in this study. The 3D seismic response of the immersed tunnel in a horizontally layered site subjected to obliquely incident waves is analyzed based on the precise dynamic stiffness matrix of the soil layer and half‐space via combined viscous‐spring boundary and equivalent node stress methods. The nonlinear effects of external and internal site conditions on the whole model were determined by equivalent linearization algorithm and Mohr–Coulomb model, respectively. The proposed model was then applied to investigate the nonlinear seismic response of an immersed tunnel in the Haihe River subjected to seismic waves of oblique incidence. The dislocation (opening) of pipe joints in the immersed tunnel were analyzed to determine the response characteristics of the shear keys and overall displacement of the tunnel; the dynamic responses of the immersed tunnel subjected to obliquely incident seismic waves markedly differ from those of vertically incident seismic SV waves. The maximum stress value of shear keys and the maximum dislocation of the pipe joint appear as upon critical angle. The overall displacement of the tunnel increases as incident angle increases. Under severe earthquake conditions, both the pipe corners and midspan section of the roof and floor are likely to produce crack. These areas need careful consideration in the seismic design of immersed tunnel structures.

Impact of Mesh and DEM Resolutions in SEM Simulation of 3D Seismic Response

This study shows that the resolution of a digital elevation model (DEM) and model mesh strongly influences 3D simulations of seismic response. Topographic heterogeneity scatters seismic waves and causes variation in seismic response (am-plification and deamplification of seismic amplitudes) at the Earth’s surface. DEM resolution influences the accuracy and detail with which the Earth’s surface can be represented and hence affects seismic simulation studies. Apart from the spatial resolution of a DEM, the mesh resolution, adopted in the creation of a 3D spectral element meshing, also changes the detailedness of surface topography. Working with high-resolution data is in most cases not possible on a regional scale because of its costliness in terms of time, money, and computation. In this study, we evaluate how low the resolution of DEM and mesh can become before the results are significantly affected. We simulated models with different combinations of DEM and mesh resolutions. The peak ground displacement (PGD) obtained from these simulations was compared with the PGD of the model with the finest mesh and DEM resolution. Our results show that any mesh or DEM resolution of 540 m or coarser will give unrealistic results. These results are valid for similar terrains as studied here and might not be directly applicable to regions with significantly different topography.

Models of the flexure-controlled strength, stiffness and cyclic deformation capacity of rectangular RC columns with smooth bars, including lap-splicing and FRP jackets

Cyclic tests of single concrete columns with smooth (plain) bars are not representative of building columns with lap splices at floor levels and story-long starter bars. Column specimens with fixity at top and bottom resemble building columns best, but few of those tested so far had smooth bars and even then without bar lap-splicing at floor level or FRP jackets at column ends. Empirical models based on single-column tests, especially the numerous ones with cantilever-type specimens, cannot be readily extended to columns with smooth bars in real-life buildings. Physical models of the Strut-and-Tie type are developed and are validated or calibrated through comparisons with laboratory tests. Their scope includes anchorage and splicing of bars with either 180° hooks or straight ends. Once validated, they are adapted to real-life multistory rectangular RC columns with smooth bars, in order to obtain the column properties of interest: the chord rotation at yielding and the cyclic ultimate chord rotation, with or without FRP jacketing. Different expressions apply to the top and bottom end of a column in a story, but a single one is used to estimate the column’s effective stiffness. Empirical alternatives fitted to the single-element test results have slightly less scatter than physical models, but caution is needed for their application to columns of real buildings. Simulations of the 3D seismic response of a plan wise asymmetric full size building, tested pseudo-dynamically before or after retrofitting all columns with FRPs or just two of them with RC jackets, provide certain confidence in the extension of the physical models for the estimation of the stiffness and ultimate deformation of columns with smooth bars in real-life buildings.

Influence of Poroelasticity on the 3D Seismic Response of Complex Geological Media

AbstractElastic wave propagation in 3D poroelastic geological media with localized heterogeneities, such as an elastic inclusion and a canyon is investigated to visualize the modification of local site responses under consideration of water saturated geomaterial. The extended computational environment herein developed is a direct Boundary Integral Equation Method (BIEM), based on the frequency-dependent fundamental solution of the governing equation in poro-visco elastodynamics. Bardet’s model is introduced in the analysis as the computationally efficient viscoelastic isomorphism to Biot’s equations of dynamic poroelasticity, thus replacing the two-phase material by a complex valued single-phase one. The potential of Bardet’s analogue is illustrated for low frequency vibrations and all simulation results demonstrate the dependency of wave field developed along the free surface on the properties of the soil material.

Full Three-Dimensional Seismic Response Analysis of Underground Structures with Large Complex Cross Sections and Two-Step Analysis Method for Reducing the Computational Costs

To enhance the reliability of estimates of seismic behavior, with a special emphasis on quality assurance of numerical simulations, this paper presents a full three-dimensional (3D) seismic response analysis of a large underground structure with a complex cross section. We conduct a full 3D seismic-response analysis using a high-fidelity model with quality assurance and a high-performance computing technique in a supercomputer environment. Due to the large computational costs of such analyses, we propose a two-step numerical simulation method based on multi-scale analysis, image-based modeling, and sophisticated approximation techniques. We provide numerical examples showing that the method can successfully reproduce the dynamic behavior of a full 3D model, but with a considerable reduction in computational costs. Our method is expected to support practical seismic safety inspections and the design of underground structures with complex large-cross-sectional configurations, as it has already been applied to the practical seismic safety inspection of an actual underground highway.

Modeling 3D time-lapse seismic response induced by CO2 by integrating borehole and 3D seismic data – A case study at the Ketzin pilot site, Germany

In order to simulate the 3D time-lapse seismic response from real data in a consistent manner detailed 3D property models at the Ketzin pilot site were constructed by robustly integrating borehole and 3D reflection seismic data. The spatial CO2 distribution and the detailed CO2 density in the reservoir were derived from dynamic flow simulations that had been history-matched to the site monitoring data. Changes in velocity and density after CO2 injection were estimated utilizing the CO2 saturation distributions at two repeat times and fluid substitution models. 4D seismic data were generated by convolving the property models at different times with an extracted wavelet.Time-lapse analysis was performed to qualitatively and quantitatively investigate the changes in reflection amplitude after CO2 injection. Comparison between the synthetic and real data at the corresponding time indicates that the 3D property models were built successfully and model the 3D time-lapse seismic response induced by CO2 injection. A synthetic experiment with two different source wavelets was implemented to investigate the impact of source non-repeatability on the seismic amplitude anomaly. Analysis shows that the same or similar sources should be used in time-lapse seismic monitoring to minimize the impact of source non-repeatability on the monitoring.