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  Subjects -> EARTH SCIENCES (Total: 621 journals)
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EARTH SCIENCES (458 journals)            First | 1 2 3 4 5     

Marine Policy     Hybrid Journal   (Followers: 33)
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Momona Ethiopian Journal of Science     Open Access   (Followers: 3)
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Mountain Research and Development     Open Access   (Followers: 3)
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Natural Hazards Review     Full-text available via subscription   (Followers: 10)
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Open Journal of Earthquake Research     Open Access  
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Ore Geology Reviews     Hybrid Journal   (Followers: 3)
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Polish Polar Research     Open Access   (Followers: 4)
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Precambrian Research     Hybrid Journal   (Followers: 5)
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Progress in Earth and Planetary Science     Open Access   (Followers: 1)
Pure and Applied Geophysics     Hybrid Journal   (Followers: 9)
Quarterly Journal of Engineering Geology and Hydrogeology     Hybrid Journal   (Followers: 5)
Quaternary Australasia     Full-text available via subscription  
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Rajshahi University Journal of Life & Earth and Agricultural Sciences     Open Access   (Followers: 1)
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Revista Boletín Ciencias de la Tierra     Open Access   (Followers: 2)
Revista Brasileira de Geofísica     Open Access   (Followers: 4)
Revista de Ingenieria Sismica     Open Access  
Revista de la Sociedad Entomologica Argentina     Open Access   (Followers: 2)
Revista de Teledetección     Open Access  
Revista de Topografía Azimut     Open Access   (Followers: 1)
Revista Eletrônica Científica Inovação e Tecnologia     Open Access  
Revista Geológica de Chile     Open Access   (Followers: 2)
River Systems     Full-text available via subscription   (Followers: 3)
Rock Mechanics and Rock Engineering     Hybrid Journal   (Followers: 6)
Rocks & Minerals     Hybrid Journal   (Followers: 2)

  First | 1 2 3 4 5     

Journal Cover   Soil Dynamics and Earthquake Engineering
  [SJR: 1.482]   [H-I: 45]   [10 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0267-7261
   Published by Elsevier Homepage  [2588 journals]
  • Determination of mean shear wave velocity to 30m depth for site
           classification using shallow depth shear wave velocity profile in Korea
    • Abstract: Publication date: June 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 73
      Author(s): Chang-Guk Sun
      The mean shear wave velocity to a depth of 30m (V S 30), established in the western United States, is the current site classification criterion for determining the seismic design ground motion, taking site amplification potential account into. To evaluate V S 30 at a site, a shear wave velocity (V S ) profile extending to a depth of at least 30m must be acquired using in situ seismic tests. In many cases, however, the obtained V S profile does not extend to a depth of 30m due to unfavorable field conditions and limitations of testing techniques. In this study, V S 30 and the mean shear wave velocity to depths less than 30m (V S Ds) were calculated using V S profiles of more than 30m obtained by seismic tests at 72 sites in Korea, and the correlation between V S 30 and V S Ds was drawn based on the computed mean V S data. Additionally, a method for extrapolating the V S profile from shallow depths to 30m and bedrock was developed by building a shape curve based on the average data of all V S profiles. These two methods of extrapolating V S 30 from shallow V S profiles, using V S Ds and a shape curve, resulted in less bias than the simple method in which the lowermost V S value obtained is extended to the depth of 30m. These two extrapolation methods are useful for V S profiles extending to depths of at least 10m. Furthermore, the shape curve method developed in this study may be useful in the western United States as well as in Korea.


      PubDate: 2015-03-14T03:10:33Z
       
  • The influence of using CFRP wraps on performance of buried steel pipelines
           under permanent ground deformations
    • Abstract: Publication date: June 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 73
      Author(s): M. Mokhtari , A. Alavi Nia
      In this study, using FRP wraps to reinforce buried steel pipelines under permanent ground deformations is investigated. For this purpose, carbon/epoxy composite wrap was used on API 5L grade X65 pipeline which is the typical material for oil and gas transportation pipelines. Mechanical behavior of the pipelines under strike-slip faulting was studied using nonlinear finite element code ABAQUS. The pipeline was supposed to be perpendicular to the fault plane. Proper performance criteria were used to determine critical fault displacements. According to defined performance criteria, critical fault displacements for different diameter to thickness ratios, various composite wrap thicknesses, and for both non-pressurized and pressurized pipelines were determined. Percentages of increase in critical fault displacements compared to non-wrapped conditions were calculated. In some pressurized pipelines, increasing strain in the ruptured area of composite wrap on the pipeline led pipeline to rupture at ultimate tensile strain of the pipe material. Results indicate that using 1-mm-thick composite wrap for non-pressurized pipelines leads critical fault displacement to increase about 100%. In addition, by increasing the thickness of composite wrap, the value of critical fault displacement increases significantly, so that applying composite wraps with thicknesses of 1 and 10mm on pressurized pipelines with diameter to thickness ratio of 144 caused critical fault displacement to increase by 154% and 892%, respectively. According to results of this research, using FRP wraps to reinforce buried steel pipelines under permanent ground deformations is recommended.


      PubDate: 2015-03-14T03:10:33Z
       
  • Improved seismic risk estimation for Bucharest, based on multiple hazard
           scenarios and analytical methods
    • Abstract: Publication date: June 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 73
      Author(s): D. Toma-Danila , C. Zulfikar , E.F. Manea , C.O. Cioflan
      Bucharest, capital of Romania, is one of the most exposed big cities in Europe to seismic damage, due to the intermediate-depth earthquakes in the Vrancea region, to the vulnerable building stock and local soil conditions. This paper tries to answer very important questions related to the seismic risk at city scale that were not yet adequately answered. First, we analyze and highlight the bottlenecks of previous risk-related studies. Based on new researches in the hazard of Bucharest (recent microzonation map and ground-motion prediction equations, reprocessed real recorded data) and in vulnerability assessment (analytical methods, earthquake loss estimation software like SELENA and ELER, the recently implemented Near Real-Time System for Estimating the Seismic Damage in Romania) we provide an improved estimation of the number of buildings and population that could be affected, for different earthquake scenarios. A new method for enhancing the spatial resolution of the building stock data is used successfully.


      PubDate: 2015-03-14T03:10:33Z
       
  • Correlations between structural damage and ground motion parameters during
           the Ms8.0 Wenchuan Earthquake
    • Abstract: Publication date: May 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 72
      Author(s): Zijun Wang , Boming Zhao
      The Wenchuan Earthquake with a magnitude of Ms 8.0 struck the Sichuan province of China on May 12, 2008, where it mainly affected the area along the Longmenshan fault. In total, 420 three-component acceleration records were obtained by the China Strong Motion Networks Centre during this seismic event, among which over 50 records exceeded 100gal. In the present study, we collected 48 near-fault acceleration records to derive strong ground motion parameters in terms of the peak ground acceleration, peak ground velocity, peak spectrum acceleration (5% of the damping ratio) and spectrum intensity (5% of damping ratio). We determined the building collapse ratios (CRs) for 20 targeted districts based on data acquired from both the China Earthquake Administration and the Chinese Academy of Sciences, where the CRs combined the data for all building types. Fragility curves were established between the CRs and the corresponding ground motion parameters, based on which the damage criteria were proposed. In particular, we derived the fragility curves for brick-concrete structures and frame-structures. These curves indicate how different structural types can determine the damage sustained. In addition, we developed a method for estimating building damage classifications. If we assume that buildings are built according to the improved Seismic Fortification Criterion in the revised “Code for Seismic Design of Buildings”, the predicted CRs for the 20 targeted districts would be significantly lower compared with the actual damage they sustained, which illustrates the validity of both the method and the revised code.


      PubDate: 2015-03-10T02:52:13Z
       
  • An approach to equivalent damping ratio of vertically mixed structures
           based on response error minimization
    • Abstract: Publication date: May 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 72
      Author(s): Wei Huang , Jiang Qian , Zhi Zhou , Qiushi Fu
      Damping property of vertically mixed structure is hard to identify, especially in the design stage since it is strongly rely on the configuration of the two component structural parts. In this paper, a decoupling approximation for dynamic response analysis of the vertically mixed structure is proposed. The optimal equivalent uniform damping ratio can be evaluated in a sense of response error minimization. It is calculated by using the superposition response spectrum method which takes the full frequency content of the ground motion into consideration rather than the harmonic excitation at a specified frequency only. The equivalent uniform damping ratios presented here are then validated by comparison with full time history analysis. Over the most part of the (R ω –R m ) parametrical plane, the response error is relatively small for the each component structural parts. And then, the proposed damping ratios are tested in actual MDOF concrete/steel irregular structures. It is shown that the proposed procedure is proved to be feasible in use for practical design.


      PubDate: 2015-03-10T02:52:13Z
       
  • Mitigation of seismic settlement of light surface structures by
           installation of sheet-pile walls around the foundation
    • Abstract: Publication date: May 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 72
      Author(s): Rouzbeh Rasouli , Ikuo Towhata , Toshihiko Hayashida
      Settlement of surface structures, which is particularly a private house, due to subsoil liquefaction is not a new issue in geotechnical engineering. It has been happening during earthquakes in liquefaction-prone areas since many years ago. However, to date no reliable measure against this problem with reasonable cost has been proposed to people. In this paper, results of a series of 1-g shaking table tests which have been conducted to evaluate performance of a possible mitigation against this problem are presented. The proposed mitigation herein is installation of sheet-pile walls around the foundation. In order to reduce the cost of mitigation, sheet-piling with gap and half-length sheet-piling were examined. The experiments were conducted in different ground water levels. It is found out that installing sheet-pile walls in relatively low ground water level can stop settlement of structures completely. Sheet-piling with gaps delays initiation of settlement but it may increase the ultimate settlement of structure. In addition, it is found that formation of a water film under the building׳s foundation is the governing mechanism of post-shaking settlement of structures.


      PubDate: 2015-03-10T02:52:13Z
       
  • A brief theory and computing of seismic ground rotations for structural
           analyses
    • Abstract: Publication date: April 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 71
      Author(s): Yuri P. Nazarov , Elena Poznyak , Anton V. Filimonov
      The seismic ground rotations are important with respect to spatial structural models, which are sensitive to the wave propagation. The rotational ground motion can lead to significant increasing of structural response, instability and unusual damages of buildings. Currently, the seismic analyses often take into account the rocking and torsion motions separately using artificial accelerograms. We present an exact analytical method, proposed by Nazarov [15] for computing of three rotational accelerograms simultaneously from given translational records. The method is based on spectral representation in the form of Fourier amplitude spectra of seismic waves, corresponding to the given three-component translational accelerogram. The composition, directions and properties of seismic waves are previously determined in the form of a generalized wave model of ground motion. It is supposed that seismic ground motion can be composed by superposition of P, SV, SH- and surface waves. As an example, the dynamic response analysis of 25-story building is presented. Here recorded (low-frequency) and artificial (high-frequency) accelerograms were used; each of them includes three translational and three rotational components. In this structural analysis, we have clarified primarily conditions under which rotational ground motion should be taken into account. Next, we have calculated three rotational components of seismic ground motion. Then they were taken as additional seismic loads components for further seismic analysis of the building. Note, soil–structure interaction (SSI) is not considered in this study. For computing, we use the special software for structural analyses and accelerogram processing (FEA Software STARK ES and Odyssey software, Eurosoft Co., Russia). It was developed and is used in engineering practice in the Central Research Institute of Building Constructions (TsNIISK, Moscow, Russia).


      PubDate: 2015-03-06T02:50:47Z
       
  • Shake table lateral earth pressure testing with dense c-ϕ backfill
    • Abstract: Publication date: April 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 71
      Author(s): Patrick Wilson , Ahmed Elgamal
      Dynamic lateral earth pressure is recorded during ten shake table testing events. In these tests, peak input acceleration at the base of the retaining wall varied in the wide range of 0.13–1.20g in order to include scenarios of relevance to recently observed strong earthquake excitations. The results shed light on the influence of soil cohesion and the effect of small wall movements on the magnitude and distribution of earth pressure. In accordance with field practice, a commonly encountered dense sand backfill with a small percentage of fines (SP-SM) is used. Inside a large soil container, earth pressure is measured against a rigid wall (backfill height H=1.7m) that is allowed to undergo limited translation/rotation due to the imparted dynamic excitation (up to 10mm or 0.006H at 1.2g base acceleration). In this particular series of experiments, favorably low dynamic pressures were recorded at backfill accelerations of up to about 0.7g in light of: (i) the relatively high soil strength (including cohesion) that precluded a limit equilibrium type failure in the backfill, and (ii) the high soil stiffness coupled with the small value of observed wall translation/rotation (as much as 3mm or 0.0018H at ground surface). In tests with instants of very high acceleration (in the range of 1g), the corresponding dynamic earth pressure is found to be of much significance for practical applications. Lateral thrusts recorded during these instants of strong shaking compare well with limit equilibrium predictions that include the soil cohesion intercept. Exclusion of the cohesion intercept results in substantial over-prediction of the measured lateral forces.


      PubDate: 2015-03-06T02:50:47Z
       
  • Large scale international testing of railway ground vibrations across
           Europe
    • Abstract: Publication date: April 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 71
      Author(s): D.P. Connolly , P. Alves Costa , G. Kouroussis , P. Galvin , P.K. Woodward , O. Laghrouche
      This paper provides new insights into the characteristics and uncertainties in railway ground-borne vibration prediction. It analyses over 1500 ground-borne vibration records, at 17 high speed rail sites, across 7 European countries. Error quantification tests reveal that existing scoping models, for at-grade tracks, are subject to a mean error of approximately ±4.5VdB. Furthermore, it is found that seemingly identical train passages are subject to a standard deviation of ±2VdB, thus providing an indicator of the minimum error potentially achievable in detailed prediction studies. Existing vibration attenuation relationships are also benchmarked and potential new relationships proposed. Furthermore, it is found that soil material properties are the most influential parameter that effect vibration levels while the effect of train speed is low. In addition, sites with train speeds close to the ‘critical velocity’ are examined and it is found that their vibration characteristics differ vastly from non-critical velocity sites. The study presents one of the most comprehensive publications of experimental ground-borne railway vibration data and comprises of datasets from Belgium, France, Spain, Portugal, Sweden, England and Italy. First, several international metrics are used to analyse the data statistically. Then the effect of train speed is investigated, with train speeds ranging from 72 to 314km/h being considered. Next the effect of train type is analysed, with correlations presented for TGV, Eurostar, Thalys, Pendolino, InterCity, X2000, Alfa Pendular, AVE-S100 and Altaria trains. Then, vibration frequency spectrums are considered and critical speed effects analysed. Finally, an investigation into the typical standard deviation encountered in vibration prediction is undertaken.


      PubDate: 2015-03-06T02:50:47Z
       
  • Analysis of the relations between slope failure distribution and seismic
           ground motion during the 2008 Wenchuan earthquake
    • Abstract: Publication date: May 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 72
      Author(s): Deping Guo , Chuan He , Chong Xu , Masanori Hamada
      The 2008 Wenchuan earthquake with M w7.9 occurred at Yingxiu County in Longmenshan thrust fault belt, southwest China, having triggered a huge amount of slope failures. This paper applied a detailed inventory with more than 190,000 slope failures and strong ground motion records of 187 seismic stations to analyze the qualitative and quantitative relations between slope failure distribution and seismic parameters. The results revealed that slope failure distribution was exponentially decreased with the increment of epicentral distance and distance from surface fault rupture; peak ground acceleration (PGA) on the hanging wall side was apparently larger than that on footwall side. Linear correlation between concentration of slope failures (LNC) and the percentage of the area affected by slope failure (LAP) and PGA was demonstrated by statistical analysis, which revealed that 0.18~0.21g horizontal PGA was the threshold value of the occurrence of slope failure. Furthermore, this paper presented an empirical model for the attenuation relation of slope failure distribution.


      PubDate: 2015-03-06T02:50:47Z
       
  • Seismic wave propagation effects on buried segmented pipelines
    • Abstract: Publication date: May 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 72
      Author(s): Peixin Shi
      This paper deals with seismic wave propagation effects on buried segmented pipelines. A finite element model is developed for estimating the axial pipe strain and relative joint displacement of segmented pipelines. The model accounts for the effects of peak ground strain, shear transfer between soil and pipeline, axial stiffness of the pipeline, joint characteristics of the pipeline, and variability of the joint capacity and stiffness. For engineering applications, simplified analytical equations are developed for estimating the maximum pipe strain and relative joint displacement. The finite element and analytical solutions show that the segmented pipeline is relatively flexible with respect to ground deformation induced by seismic waves and deforms together with the ground. The ground strain within each pipe segmental length is shared by the joint displacement and pipe barrel strain. When the maximum ground strain is higher than 0.001, the pipe barrel strain is relatively small and can be ignored. The relative joint displacement of the segmented pipeline is mainly affected by the variability of the joint pullout capacity and accumulates at locally weak joints.


      PubDate: 2015-03-06T02:50:47Z
       
  • Experimental investigation into ground vibrations induced by very high
           speed trains on a non-ballasted track
    • Abstract: Publication date: May 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 72
      Author(s): Wanming Zhai , Kai Wei , Xiaolin Song , Minghe Shao
      A field measurement of ground vibration was performed on the Beijing−Shanghai high-speed railway in China. In this paper, the experimental results of vertical ground vibration accelerations induced by very high speed trains running over a non-ballasted track on embankment with speeds from 300 to 410km/h are reported and analyzed in detail for the first time. Characteristics of ground vibration accelerations in both time and frequency domains are analyzed based on the test data. It is shown that the periodic exciting action of high-speed train bogies can be identified in time histories of vertical accelerations of the ground within the range of 50m from the track centerline. The first dominant sensitive frequency of the ground vibration acceleration results from the wheelbase of the bogie, and the center distance of two neighboring cars plays an important role in the significant frequencies of the ground vibration acceleration. Variations of time–response peak value and frequency-weighted vertical acceleration level of ground vibration in relation with train speed as well as the distance from the track centerline are also investigated. Results show that the time-domain peak value of ground vibration acceleration exhibits an approximately linear upward tendency with the increase of train speed. With the increasing distance from the track centerline, the frequency-weighted vertical acceleration level of the ground vibration attenuates more slowly than the time-domain peak value of the ground vibration acceleration does. Severe impact of high-speed railway ground vibration on human body comfort on the ground occurs at the speed of 380–400km/h. The results given in the paper are also valuable for validating the numerical prediction of train induced ground vibrations.


      PubDate: 2015-03-06T02:50:47Z
       
  • Seismic sequence effects on three-dimensional reinforced concrete
           buildings
    • Abstract: Publication date: May 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 72
      Author(s): Maria Hatzivassiliou , George D. Hatzigeorgiou
      Repeated earthquakes strongly affect the inelastic response of structures and cause in many cases more adverse effects in comparison with the corresponding single ground motions, such as the accumulation of structural and non-structural damage as well as the increment of deformation demands. Numerous research studies have been recently published in the pertinent literature to investigate this phenomenon but most of them are limited either to single-degree-of-freedom (SDOF) systems or to two-dimensional multi-degree-of freedom (2-D MDOF) systems such as multi-storey planar framed structures. With special regard to reinforced concrete (RC) buildings, this study investigates for the first time the inelastic response of three-dimensional (3-D) structures subjected to repeated earthquakes. More specifically, two three-storey and two five-storey RC buildings, which are regular and irregular along their height, are examined under five real strong multiple earthquakes where their two horizontal components as well as the vertical one are taken into account. The investigation focuses on the examination of the maximum displacements, maximum residual displacements, maximum interstorey drift ratio, maximum residual interstorey drift ratio, damage indices and ductility demands. Finally, the building structures under consideration are analyzed for different siting configurations to investigate the effect of earthquake direction incident. It is concluded that the multiplicity of earthquakes should be taken into account for the reliable seismic design of reinforced concrete structures.


      PubDate: 2015-03-06T02:50:47Z
       
  • 2D numerical investigation of segmental tunnel lining under seismic
           loading
    • Abstract: Publication date: May 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 72
      Author(s): Ngoc-Anh Do , Daniel Dias , Pierpaolo Oreste , Irini Djeran-Maigre
      Segmental tunnel linings are now often used for seismic areas. However, the influence of segment joints on the segmental lining behavior under seismic loading has not been thoroughly considered in the literature. This paper presents a numerical study, which has been performed under seismic circumstance, to investigate the factors that affect segmental tunnel lining behavior. Analyses have been carried out using a two-dimensional finite difference element model. The proposed model allows studying the effect of the rotational joint stiffness, radial stiffness and the axial stiffness of the longitudinal joints. The numerical results show that a segmental lining can perform better than a continuous lining during earthquake. It has been seen that the influence of the joint distribution, the joint rotational stiffness, the joint axial stiffness, Young׳s modulus of the ground surrounding the tunnel, the lateral earth pressure factor and the maximum shear strain should not be neglected. Some important differences of the segmental tunnel lining behavior under static and seismic conditions have been highlighted.


      PubDate: 2015-03-06T02:50:47Z
       
  • Pipe–soil interaction and pipeline performance under
           strike–slip fault movements
    • Abstract: Publication date: May 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 72
      Author(s): Polynikis Vazouras , Panos Dakoulas , Spyros A. Karamanos
      The performance of pipelines subjected to permanent strike–slip fault movement is investigated by combining detailed numerical simulations and closed-form solutions. First a closed-form solution for the force–displacement relationship of a buried pipeline subjected to tension is presented for pipelines of finite and infinite lengths. Subsequently the solution is used in the form of nonlinear springs at the two ends of the pipeline in a refined finite element model, allowing an efficient nonlinear analysis of the pipe–soil system at large strike–slip fault movements. The analysis accounts for large strains, inelastic material behavior of the pipeline and the surrounding soil, as well as contact and friction conditions on the soil–pipe interface. The numerical models consider infinite and finite length of the pipeline corresponding to various angles β between the pipeline axis and the normal to the fault plane. Using the proposed closed-form nonlinear force–displacement relationship for buried pipelines of finite and infinite length, axial strains are in excellent agreement with results obtained from detailed finite element models that employ beam elements and distributed springs along the pipeline length. Appropriate performance criteria of the steel pipeline are adopted and monitored throughout the analysis. It is shown that the end conditions of the pipeline have a significant influence on pipeline performance. For a strike–slip fault normal to the pipeline axis, local buckling occurs at relatively small fault displacements. As the angle between the fault normal and the pipeline axis increases, local buckling can be avoided due to longitudinal stretching, but the pipeline may fail due to excessive axial tensile strains or cross sectional flattening. Finally a simplified analytical model introduced elsewhere, is enhanced to account for end effects and illustrates the formation of local buckling for relative small values of crossing angle.


      PubDate: 2015-03-06T02:50:47Z
       
  • Dynamic effects of surface fault rupture interaction with structures
    • Abstract: Publication date: May 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 72
      Author(s): Nicolas K. Oettle , Jonathan D. Bray , Douglas S. Dreger
      Surface fault rupture has caused significant damage to structures in several earthquakes. The propagation of the bedrock fault rupture through the overlying soil deposit has been studied by several researchers; however, the effects of fault rupture dynamics, as opposed to pseudostatic fault movement, have not yet been evaluated. There is the potential for dynamic effects to influence significantly structural damage due to the rapid rate of deformation imposed by surface fault rupture. Numerical simulations are performed to analyze the effects of the rate of fault rupture on dip-slip surface fault rupture for free-field and soil-structure interaction conditions. The numerical results indicate that in some limited scenarios, fault rupture dynamics can influence the amount of structural damage expected for a structure located near a fault. However, in most scenarios, fault rupture dynamics is expected to play a secondary role compared to fault, soil, and structural characteristics in evaluating building performance.


      PubDate: 2015-03-06T02:50:47Z
       
  • Multifractal characteristic analysis of near-fault earthquake ground
           motions
    • Abstract: Publication date: May 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 72
      Author(s): Dixiong Yang , Changgeng Zhang , Yunhe Liu
      This study aims to reveal the multi-scaling behavior and quantify the irregularity of near-fault earthquake ground motions from a new perspective of multifractal theory. Based on multifractal detrended fluctuation analysis, the multifractal characteristic parameters of acceleration time series for typical near-fault ground motions are calculated, and their correlations with two period parameters (i.e., mean period T m and characteristic period T c) and box-counting fractal dimensions are analyzed. Numerical results of strong nonlinear dependence of generalized Hurst exponents h(q) upon the fluctuation orders q indicate that near-fault ground motions present the multifractal properties and long-range correlation obviously. Furthermore, the scaling exponent h(2) of near-fault records has a strong correlation with their periods T m and T c, and strongly negative correlation with their box dimension. Moreover, h(2) can be regarded as a measure of frequency content and irregularity degree of strong earthquake ground motions. Finally, it is pointed out that the long-range correlation of small and large fluctuation is the major source of multifractality of near-fault ground motions.


      PubDate: 2015-03-06T02:50:47Z
       
  • Micro- and macro-observations of liquefaction of saturated sand around
           buried structures in centrifuge shaking table tests
    • Abstract: Publication date: May 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 72
      Author(s): Jian Zhou , Jianhong Jiang , Xiaoliang Chen
      A novel experimental method was designed to study the micro-behavior of saturated sand around a buried structure in centrifuge shaking table tests under strong simulated earthquake loading, in addition to the traditional macro-measurements. One free field test was first carried out as a reference, followed by one test with a deep buried structure and one with a shallowly buried structure. During the tests with the buried structure, high quality pictures of moving sand around the structure were recorded by a newly developed image acquisition system. By analyzing the interesting pictures at reasonable intervals using an image analysis software, the evolutions of microstructural features were obtained such as the orientations of the long axes of particles, the orientations of contact normals between particles and the average contact number of the interesting group of particles. The results showed that the evolutions of the micro-features were consistent with those of the macro-measurements such as excess pore pressures and accelerations, which help illuminate the mechanism of sand liquefaction.


      PubDate: 2015-03-06T02:50:47Z
       
  • The energy factor of systems considering multiple yielding stages during
           ground motions
    • Abstract: Publication date: April 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 71
      Author(s): Ke Ke , Shuizhou Ke , Guanghong Chuan
      This communication focuses on the energy factors of systems considering multiple yielding stages during ground motions. Based on an improved energy-balance model, the energy balance of systems is re-established and the energy factor is derived, considering the multiple yielding stages. To comprehensively investigate the influence of yielding stages and critical parameters on the energy factor, nonlinear dynamic analyses of single-degree-of-freedom systems are performed based on the validated numerical tool. Representative numerical evaluations are presented for different combinations of parameters denoting the yielding stages. The results indicate that the energy factor is significantly influenced by the yielding stages of systems. The results of this study are instructive for the calculation of the energy factor of systems showing multiple yielding stages during ground motions, and can be helpful to improve the current procedures based on the energy-balance concept.


      PubDate: 2015-03-06T02:50:47Z
       
  • Analysis of a buried pipeline subjected to fault displacement: A DEM and
           FEM study
    • Abstract: Publication date: April 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 71
      Author(s): Md. Aftabur Rahman , Hisashi Taniyama
      Buried pipelines are commonly used to transport oil, water, sewage, and natural gas and are referred as lifeline systems. The 3D discrete element method (DEM) analysis was carried out to examine the response of buried pipeline owing to fault movement. Approximately 1.8 million spherical particles, which were considered to represent soil and a hollow circular pipe, were placed at a shallow depth in the proposed numerical model. The DEM simulation was performed for the sedimentation of soil particles, and fault displacements were subsequently assigned to the model. The force–displacement relation between pipes and particles is important in the modeling and design of buried pipes in the vicinity of faults. The present study discusses the force–displacement relation between pipes and particles in the axial and vertical directions for fault movement. This relation reveals the strain softening behavior of particles near the fault crossing point. The interaction between soil particles and pipe elements can be understood from this numerical simulation. Particles push the pipes and have a greater effect near the rupture point. Finally, a parametric study was performed using different pipe properties, and the responses were analyzed.


      PubDate: 2015-03-06T02:50:47Z
       
  • Seismic ground amplification by unlined tunnels subjected to vertically
           propagating SV and P waves using BEM
    • Abstract: Publication date: April 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 71
      Author(s): Hamid Alielahi , Mohsen Kamalian , Mohammad Adampira
      Recent researches have revealed that the seismic ground response above tunnels can be different from the free-field motion during earthquakes. Nevertheless, to the best of the authors׳ knowledge, neither building codes nor seismic microzonation guidelines have yet considered this matter. In the present study, the seismic response of a linear elastic medium including a buried unlined tunnel subjected to vertically propagating incident SV and P waves are addressed. For analysis purposes, a numerical time-domain analysis is performed by utilizing a robust numerical algorithm working based on the boundary element method. It is observed that the amplification of the ground surface underlain by a tunnel is increased in long periods. The variation of the amplification factor and characteristic period of the medium versus the buried depth of the tunnel are depicted as the major results of this study. Some simple and useful relations are proposed for estimating the seismic microzonation of the areas underlain by tunnels. These relations can also be used for the preliminary seismic design of structures located on underground structures.


      PubDate: 2015-03-06T02:50:47Z
       
  • Dynamic response of a partially debonded pipeline embedded in a saturated
           poroelastic medium to harmonic plane waves
    • Abstract: Publication date: April 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 71
      Author(s): Xue-Qian Fang , Jin-Xi Liu , Yang Wang
      A practical model of partially debonded pipeline embedded in a saturated poroelastic medium is proposed, and the dynamic response of this model to harmonic plane waves is theoretical investigated. Biot׳s poroelastic theory is introduced to describe the dynamic equations of the saturated poroelastic medium, and the potentials obtained from Helmholtz decomposition theorem are expressed by wave function expansion method. The debonding areas around the pipeline are assumed to be filled with water. The disturbed solutions of basic field equations in these areas are expressed in terms of a scalar velocity potential. Different boundary conditions of bonded and debonded areas are adopted, and the expanded coefficients are obtained. An example of one partially debonded area is presented and analyzed. It is found that the stresses in the perfectly bonded and debonded areas show great difference, and the jump of dynamic stress at the connection points between these two areas is great in the case of low frequency. The effect of debonded areas on the dynamic stress under different thicknesses of lining is also examined.


      PubDate: 2015-03-06T02:50:47Z
       
  • Seismic response of bridges with massive foundations
    • Abstract: Publication date: April 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 71
      Author(s): Juan M. Mayoral , Miguel P. Romo
      The dynamic response of vehicular overpasses with massive foundations built in highly populated earthquake prone regions is studied to assess the massive foundation potential of being a technically sound mean to reduce the structural response during major earthquakes. The study consists on numerical simulations using 3-D finite element models. Two typical supports of a major 23km long vehicular overpass recently built in the north east part of Mexico City valley were considered in this research. This zone is characterized by the presence of stiff soils comprised by dense and very dense silty sands and sandy silts, randomly intercalated by stiff clays layers of variable thickness. Initially, a conventional raft foundation structurally connected to four precast closed-end concrete piles was considered. Then, the potential beneficial effect of a massive foundation of variable depth was assessed. Sets of 3-D finite element models were developed and the response of the systems was evaluated for a typical seismic scenario such as that prevailing at the zone, assuming a potential 8.1 M w seismic event, and for a hypothetical 8.7 M w extreme event. Important attenuations of about 39% to 48% at the upper deck spectral accelerations and of 21% to 30% in maximum lateral foundation displacements were achieved with the massive soil improvement for the cases analyzed. Thus, the massive foundations seem to be a convenient alternative to reduce the overall structural seismic response.
      Graphical abstract image

      PubDate: 2015-03-06T02:50:47Z
       
  • Novel adaptive time stepping method and its application to soil seismic
           liquefaction analysis
    • Abstract: Publication date: April 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 71
      Author(s): X.W. Tang , X.W. Zhang , R. Uzuoka
      In solid–fluid coupled and dynamic analysis, the temporal discretization error related to the time step size is unavoidable. To improve the calculation efficiency, a novel adaptive time stepping procedure based on a finite element and finite difference (FEM–FDM) coupled method is proposed for soil seismic liquefaction analysis. The core concept of this adaptive stepping method is the mixed displacement and pore water pressure error estimation, which is obtained by an embedded error estimator, and a time stepping strategy, which is operated according to the relation between the current mixed error and the prescribed error tolerance. Two numerical examples were performed to validate the proposed method. It is shown that under the same condition of mesh size and other numerical parameters, the time step size obviously affects the calculation results; using adaptive stepping method is economical, robust and has the same degree of accuracy as compared with the fixed stepping method in the soil earthquake liquefaction analysis.


      PubDate: 2015-03-06T02:50:47Z
       
  • The modified and extended upper-bound (UB) pushover method for the
           multi-mode pushover analysis of unsymmetric-plan tall buildings
    • Abstract: Publication date: April 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 71
      Author(s): Mehdi Poursha , Esmaiel Talebi Samarin
      Upper-bound (UB) pushover analysis method, which was proposed to consider the effect of higher modes for two-dimensional (2D) tall building frames, underestimates the seismic demands at the lower storeys. In this study, the limitation of the method is resolved by combining the seismic demands resulting from the upper-bound pushover method and a conventional pushover analysis that the latter controls the seismic demands at the lower storeys. Furthermore, the main aim of this study is the extension of the upper-bound pushover analysis method to unsymmetric-plan tall buildings to take torsional effects into account. The extension is carried out based on the use of upper-bound lateral forces with different patterns for various unsymmetric-plan tall buildings. The upper-bound of the contribution ratio of higher modes is considered in computing the upper-bound lateral forces. The results elucidate that the extended method can predict to a reasonable accuracy the inelastic seismic demands of unsymmetic-plan tall buildings.


      PubDate: 2015-03-06T02:50:47Z
       
  • A GLE-based model for seismic displacement analysis of slopes including
           strength degradation and geometry rearrangement
    • Abstract: Publication date: April 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 71
      Author(s): Valeria Bandini , Giovanni Biondi , Ernesto Cascone , Sebastiano Rampello
      Seismic performance of natural slopes, earth structures and solid-waste landfills can be evaluated through displacement-based methods in which permanent displacements induced by earthquake loading are assumed to progressively develop along the critical sliding surface as a result of transient activation of plastic mechanisms within the soil mass. For sliding mechanisms of general shape the earthquake-induced displacements should be computed using a model that provides a closer approximation of sliding surface. When large permanent displacement are induced by seismic actions, due to substantial shear strength reduction, and significant changes in ground surface occur, an improved estimate of permanent displacement can be obtained using a model which accounts for shear strength reduction and mass transfer between adjacent portions of the slope resulting from geometry changes of ground surface during the seismic event. In this paper, a GLE-based model is proposed for seismic displacement analysis of slopes that accounts for shear strength degradation and for geometry rearrangement. Model accuracy is validated against experimental results obtained from shaking table tests carried out on small scale model slopes. Comparison of computed and experimental results demonstrates the capability of the proposed approach in capturing the main features of the observed seismic response of the model slopes.


      PubDate: 2015-03-06T02:50:47Z
       
  • Seismic hazard evaluation in Anjar city area of western India: Microtremor
           array measurement
    • Abstract: Publication date: April 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 71
      Author(s): A.P. Singh
      In western India during the Bhuj earthquake (Mw 7.6) on January 26, 2001, the Anjar City at ~30km southwest of Bhuj experienced three types of damage scenario: severely damaged, less damaged and non-damaged. Similar damage patterns were also observed for the 1819 (Mw 7.8) and the 1956 (Mw 6.0) earthquakes. Microtremor array measurements were conducted in and around the Anjar city to examine the strength of soil structures and damage pattern. Significant differences are observed in frequencies and amplitudes in horizontal-to-vertical spectral ratio (HVSR) using microtremor measurements. The severely- damaged site shows two peak amplitudes: 2.8 at 1.2Hz; and 4.0 at 8.0Hz. The less-damaged site also shows two amplitudes: 2.5 and 2.1 at 1.4Hz; and 2.0Hz, respectively. The non-damaged site, on the other hand, shows that the HVSR curves become almost flatter. Similar results for three types of damage scenario based on analyses of earthquake records are also observed for the study area. The microtremor array measurements has revealed shear wave velocity V s ≥400m/s at 18m depth in the non-damaged, at 40m in the less-damaged and at 60m depth in the severely-damaged sites. The site amplitudes and the V s values show a good correlation with the soil characteristics and damage pattern, suggesting that strength of soil layers at varying depths is a dictating factor for the estimate of the earthquake risk evaluation of the area under study.


      PubDate: 2015-03-06T02:50:47Z
       
  • Seismic response of self-centering prestressed concrete moment resisting
           frames with web friction devices
    • Abstract: Publication date: April 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 71
      Author(s): Liang-Long Song , Tong Guo , Zhi-Liang Cao
      This paper examines the seismic response of self-centering prestressed concrete moment resisting frames (SCPC-MRFs) with web friction devices. Nonlinear dynamic analyses under ground motion ensembles corresponding to two seismic hazard levels are performed. The results of SCPC-MRFs are compared with those of monolithic reinforced concrete (RC) MRFs in terms of global and local responses. Seismic analyses results show that SCPC-MRFs generally experience similar peak story drifts, less beam end rotations, and much smaller residual deformations as compared with those of RC-MRFs. However, it is also found that SCPC-MRFs sustained larger column plastic rotations than RC-MRFs and are more sensitive to the formation of a soft story. In general, the 8-story SCPC-MRFs show better seismic performances than the 4-story ones. Mainshock–aftershock analyses show that the incremental effect of aftershock on damage extent is much smaller for the SCPC-MRFs than for the RC-MRFs.


      PubDate: 2015-03-06T02:50:47Z
       
  • Non-linear transient behavior during soil liquefaction based on
           re-evaluation of seismic records
    • Abstract: Publication date: April 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 71
      Author(s): S. Kamagata , I. Takewaki
      Focusing on soil liquefaction, the seismic records during the Niigata-ken earthquake in 1964, the southern Hyogo prefecture earthquake in 1995 and the 2011 off the Pacific coast of Tohoku earthquake are analyzed by the non-stationary Fourier spectra. The shift of dominant frequency in the seismic record of Kawagishi-cho during the Niigata-ken earthquake is evaluated based on the time-variant property of dominant frequencies. The reduction ratio of the soil stiffness is evaluated from the shift ratio of dominant frequency. It is detected that the pulse wave in the transient process during the progressing liquefaction is composed of the primary mode and the secondary modes. Using the seismic records at the underground of Port Island during the southern Hyogo prefecture earthquake in 1995, the amplification of liquefaction is evaluated by comparing the maximum amplitude spectra of seismic records at GL 0m and GL-83m. The average shear strain of underground is calculated from the numerically integrated displacement profiles and the deterioration ratio of stiffness is evaluated from the G- γ relation. The amplification of liquefaction at Chiba bay area is evaluated by using the ratio of the maximum amplitude spectra of CHB024 and CHBH10 (Borehole) from the mainshock and the aftershock of the 2011 off the Pacific coast of Tohoku earthquake.


      PubDate: 2015-03-06T02:50:47Z
       
  • The influence of the degree of saturation on dynamic response of a
           cylindrical lined cavity in a nearly saturated medium
    • Abstract: Publication date: April 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 71
      Author(s): Y. Wang , G.Y. Gao , J. Yang , J. Song
      In most previous studies on the dynamic response of a long cylindrical cavity subjected to internal transient dynamic loads, the porous medium was usually assumed to be completely saturated by ground water. In practice, however, the full saturation condition does not always exist. In this paper the surrounding soil and the lining of the cavity are respectively treated as a nearly saturated porous medium and an elastic material, and the governing equations for the dynamic problem are derived. A set of exact solutions are obtained in the Laplace transform domain for three types of transient loads, i.e. suddenly applied constant load, gradually applied step load and triangular pulse load. By utilizing a reliable numerical method of inverse Laplace transforms, the time-domain solutions are then presented. The influence of the degree of saturation of the surrounding soil on the dynamic response of the lined cavity is examined for numerical examples.


      PubDate: 2015-03-06T02:50:47Z
       
  • CPT-based analysis of liquefaction and re-liquefaction following the
           Canterbury earthquake sequence
    • Abstract: Publication date: Available online 2 March 2015
      Source:Soil Dynamics and Earthquake Engineering
      Author(s): J.J. Lees , R.H. Ballagh , R.P. Orense , S. van Ballegooy
      The Canterbury region experienced widespread damage due to liquefaction induced by seismic shaking during the 4 September 2010 earthquake and the large aftershocks that followed, notably those that occurred on 22 February, 13 June and 23 December 2011. Following the 2010 earthquake, the Earthquake Commission directed a thorough investigation of the ground profile in Christchurch, and to date, more than 7500 cone penetration tests (CPT) have been performed in the region. This paper presents the results of analyses which use a subset of the geotechnical database to evaluate the liquefaction process as well as the re-liquefaction that occurred following some of the major events in Christchurch. First, the applicability of existing CPT-based methods for evaluating liquefaction potential of Christchurch soils was investigated using three methods currently available. Next, the results of liquefaction potential evaluation were compared with the severity of observed damage, categorised in terms of the land damage grade developed from Tonkin & Taylor property inspections as well as from observed severity of liquefaction from aerial photography. For this purpose, the Liquefaction Potential Index (LPI) was used to represent the damage potential at each site. In addition, a comparison of the CPT-based strength profiles obtained before each of the major aftershocks was performed. The results suggest that the analysis of spatial and temporal variations of strength profiles gives a clear indication of the resulting liquefaction and re-liquefaction observed in Christchurch. The comparison of a limited number of CPT strength profiles before and after the earthquakes seems to indicate that no noticeable strengthening has occurred in Christchurch, making the area vulnerable to liquefaction induced land damage in future large-scale earthquakes.


      PubDate: 2015-03-06T02:50:47Z
       
  • Coherence of dispersed synthetic strong earthquake ground motion at small
           separation distances
    • Abstract: Publication date: March 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 70
      Author(s): Haiping Ding , Mihailo D. Trifunac , Maria I. Todorovska , Nebojša Orbović
      It is shown that the observed loss of coherency of synthetic strong motion on ground surface for separation distances less than about 100m can be described in terms of the dispersion of strong motion waves. Additional contributions to the loss of coherency from variations of material properties in the soil and from geometrical departures from perfectly flat ground surface and irregular layer geometries are not considered in this paper. It is also shown that the synthetic surface displacements over a large rectangular area (100×100m) on ground surface can be described well by a flat surface undergoing translations and rotations only, and with only minor departures from the plane flat surface.


      PubDate: 2015-03-06T02:50:47Z
       
  • Elastic waves in continuous and discontinuous geological media by boundary
           integral equation methods: A review
    • Abstract: Publication date: March 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 70
      Author(s): George D. Manolis , Petia S. Dineva
      In this review paper, we concentrate on the use of boundary integral equation (BIE) based methods for the numerical modeling of elastic wave motion in naturally occurring media. The main reason for using BIE is the presence of the free surface of the earth, whereby large categories of problems involve continua with a small surface to volume ratio. Given that under most circumstances, BIE require surface discretization only, substantial savings can be realized in terms of the size of the mesh resulting from the discretization procedure as compared to domain-type numerical methods. We note that this is not necessarily the case with man-made materials that have finite boundaries. Thus, although the emphasis here is on wave motion in geological media, this review is potentially of interest to researchers working in other scientific fields such as material science. Most of the material referenced in this reviews drawn from research work conducted in the last fifteen years, i.e., since the year 2000, but for reasons of completeness reference is made to seminal papers and books dating since the early 1970s. Furthermore, we include here methods other than the BIE-based ones, in order to better explain all the constituent parts of hybrid methods. These have become quite popular in recent years because they seem to combine the best features of surface-only discretization techniques with those of domain type approaches such as finite elements and finite differences. The result is a more rounded approach to the subject of elastic wave motion, which is the underlying foundation of all problems that have to do with time-dependent phenomena in solids.


      PubDate: 2015-03-06T02:50:47Z
       
  • Evaluation of active and passive seismic earth pressures considering
           internal friction and cohesion
    • Abstract: Publication date: March 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 70
      Author(s): Shi-Yu Xu , Anoosh Shamsabadi , Ertugrul Taciroglu
      The Log-Spiral-Rankine (LSR) model, which is a generalized formulation for assessing the active and passive seismic earth pressures considering the internal friction and cohesion of backfill soil, is reviewed and improved in this study. System inconsistencies in the LSR model are identified, which result from an inaccurate assumption on the vertical normal stress field (σ z =γz) in a general c–ϕ soil medium, and from omitting the effect of soil cohesion when solving for the stress states along the failure surface. The remedies to the said inconsistencies are presented, and local and global iteration schemes are introduced to solve the resulting highly coupled multivariate nonlinear system of equations. The modified LSR model provides a more complete and accurate solution for earth retaining systems, including the geometry of the mobilized soil body, the stress state along the failure surface, as well as the magnitude and the point of application of the resultant earth thrust.


      PubDate: 2015-03-06T02:50:47Z
       
  • General formulation and solution procedure for harmonic response of rigid
           foundation on isotropic as well as anisotropic multilayered half-space
    • Abstract: Publication date: March 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 70
      Author(s): Gao Lin , Zejun Han , Jianbo Li
      A general formulation and solution procedure are proposed for harmonic response of rigid foundation on multilayered half-space. It is suitable for isotropic as well as anisotropic soil medium. The wave motion equation is formulated in frequency wave-number domain in the state space. A hybrid approach is proposed for its solution, where the precise integration algorithm (PIA) is employed to carry out the integration. Very high accuracy can be achieved. The mixed variable form of wave motion equation enables the assembly of layers simple and convenient. The surface Green׳s function is regarded as rigorous, because it is free from approximations and discretization errors. The algorithm is unconditionally stable. The numerical implementation is based on algebraic matrix operation. Numerical examples of vibration of rigid foundation validate the efficiency and accuracy of the proposed approach.
      Graphical abstract image

      PubDate: 2015-03-06T02:50:47Z
       
  • Cyclic secant shear modulus versus pore water pressure in sands at small
           cyclic strains
    • Abstract: Publication date: March 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 70
      Author(s): Mladen Vucetic , Ahmadreza Mortezaie
      Cyclic strain-controlled behavior of fully saturated sands in undrained condition is analyzed at small cyclic shear strain amplitudes, γ c, around the threshold shear strain for cyclic pore water pressure buildup, γ tp≈0.01%. The cyclic triaxial and simple shear test results obtained in the past by different researchers and the results of new cyclic simple shear tests reveal that: (i) at very small γ c below γ tp where there is no buildup of cyclic pore water pressure, Δu N, with the number of cycles, N, the cyclic secant shear modulus, G SN, initially increases with N for 10–20% of its initial value G S1 and then levels off or just slightly decreases, (ii) at small γ c between γ tp≈0.01% and 0.10–0.15%, Δu N continuously increases with N while the modulus G SN first increases for up to 10% of G S1 and then gradually decreases, and (iii) at γ c larger than approximately 0.15%, relatively large Δu N develops with N while the modulus G SN constantly and significantly decreases. This means that at γ c between γ tp and 0.10–0.15% the sand stiffness initially increases with N in spite of the reduction of effective stresses caused by the cyclic pore water pressures buildup. In this range of γ c, the pore water pressure Δu N can reach up to 40% of the initial effective confining stress before G SN drops below G S1. The microstructural mechanisms believed to be responsible for such a complex behavior are discussed. It is suggested that during cyclic loading the changes at mineral-to-mineral junctions of grain contacts can cause soil stiffening while, at the same time, the buildup of cyclic pore water pressure causes the softening.


      PubDate: 2015-03-06T02:50:47Z
       
  • Discussion of the paper: “Recommendations for extension and
           re-calibration of an existing sand constitutive model taking into account
           varying non-plastic fines content”
    • Abstract: Publication date: March 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 70
      Author(s): Md Mizanur Rahman , S.R. Lo



      PubDate: 2015-03-06T02:50:47Z
       
  • Combined paraxial-consistent boundary conditions finite element model for
           simulating wave propagation in elastic half-space media
    • Abstract: Publication date: March 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 70
      Author(s): N. Hamdan , O. Laghrouche , P.K. Woodward , A. El-Kacimi
      In this paper, a finite element model of a soil island is coupled to both a consistent transmitting boundary and a paraxial boundary, which are then used to model the propagation of waves in semi-infinite elastic layered media. The formulation is carried out in the frequency domain while assuming plane strain conditions. It is known that a discrete model of this type, while providing excellent results for a wide range of physical parameters in the context of a half-space problem, may deteriorate rapidly at low frequencies of excitation. This is so because at low frequencies the various waves in the model eventually attain characteristic wavelengths which exceed the distance of the bottom boundary, which then causes that boundary to fail. Also, the paraxial boundaries themselves break down at very low frequencies. In this paper, this difficulty is overcome and the model׳s performance is improved upon dramatically by incorporating an artificial buffer layer sandwiched between the bottom of the soil medium and the underlying elastic half-space. Applications dealing with rigid foundations resting on homogenous or layered half-space media are shown to exhibit significant improvement. Following extensive simulations, clear guidelines are provided on the performance of the coupled model and an interpretation is given on the engineering significance of the findings. Finally, clear recommendations are provided for the practical use of the proposed modelling strategy.


      PubDate: 2015-03-06T02:50:47Z
       
  • Mechanism and bounding of earthquake energy input to building structure on
           surface ground subjected to engineering bedrock motion
    • Abstract: Publication date: March 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 70
      Author(s): K. Kojima , K. Sakaguchi , I. Takewaki
      The mechanism of earthquake energy input to building structures is clarified by considering the surface ground amplification and soil–structure interaction. The earthquake input energies to superstructures, soil–foundation systems and total swaying–rocking system are obtained by taking the corresponding appropriate free bodies into account and defining the energy transfer functions. It has been made clear that, when the ground surface motion is white, the input energy to the swaying–rocking model is constant regardless of the soil property (input energy constant property). The upper bound of earthquake input energy to the swaying–rocking model is derived for the model including the surface ground amplification by taking full advantage of the above-mentioned input energy constant property and introducing the envelope function for the transfer function of the surface ground amplification. Extension of the theory to a general earthquake ground motion model at the engineering bedrock is also made by taking full advantage of the above-mentioned input energy constant property.


      PubDate: 2015-03-06T02:50:47Z
       
  • Soil-structure interaction using BEM–FEM coupling through ANSYS
           software package
    • Abstract: Publication date: March 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 70
      Author(s): G. Vasilev , S. Parvanova , P. Dineva , F. Wuttke
      The main aim of this work is to develop, verify and apply in simulation study an efficient hybrid approach to study seismic response of a soil-structure system taking into account all the important components as: (1) the line time-harmonic source with its specific geophysical properties; (2) the inhomogeneity and heterogeneity of the wave path from the source to the local geological region; (3) the geotechnical properties of the near-field local geological profile and finally (4) the properties of the engineering structure itself. Plane strain state is considered. The hybrid computational tool is based on the boundary element method (BEM 1 1 Boundary element method. ) for modeling the infinite far-field geological media and finite element method (FEM 2 2 Finite element method. ) for treating the dynamic behavior of the structure and the near-field finite soil geological region. Each of the two techniques is applied in that part of the whole model where it works more efficiently. The hybrid numerical scheme is realized via the sub-structure approach, direct BEM1, conventional FEM2 and insertion of the BEM1 model of the seismically active far-field geological media as a macro-finite element (MFE 3 3 Macro-finite element. ) in the FEM2 commercial program ANSYS. The accuracy and verification study of the proposed method is presented by solution of numerical test examples simulating different seismic scenarios. The obtained results show clearly that the hybrid model is able to demonstrate the sensitivity of the synthetic signals to the source properties, to the heterogeneous character of the wave path, to the relief peculiarities of the local layered geological deposit and to the specific properties of the engineering structure.


      PubDate: 2015-03-06T02:50:47Z
       
  • Improved simplified calibration procedure for a high-cycle accumulation
           model
    • Abstract: Publication date: March 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 70
      Author(s): T. Wichtmann , A. Niemunis , T. Triantafyllidis
      The high-cycle accumulation (HCA) model proposed by Niemunis et al. [16] predicts permanent deformations due to a drained cyclic loading with many small cycles (i.e. N ≥ 10 3 cycles with strain amplitudes ε ampl ≤ 10 − 3 ). The strain amplitude is the most important influencing parameter of the rate of strain accumulation ε ̇ acc . Based on tests on a medium coarse sand, a square relationship ε ̇ acc ~ ( ε ampl ) 2 has been used in the HCA model so far. The new test results presented in this paper indicate, however, that the exponent of the amplitude-dependence may vary between 1.3 and 2.4, depending on the tested material. This comes out of 150 drained cyclic triaxial tests with 105 load cycles performed on 14 clean quartz sands with specially mixed grain size distribution curves. Consequently, an additional material constant C ampl has been introduced into the HCA model describing the amplitude dependence according to ε ̇ acc ~ ( ε ampl ) C ampl . The additional parameter requires a revision of the simplified calibration procedure proposed by Wichtmann et al. [24] which uses correlations between the HCA model parameters and granulometric (d 50, C u ) or index properties ( e min ). Furthermore, the new cyclic test data reveal that the existing correlations are inappropriate for well-graded granular materials ( C u ≥ 5 ). Enhanced correlations suitable also for more well-graded sands are proposed in the paper. The possible error of a HCA model prediction with parameters fully or partly determined from the correlations is discussed.


      PubDate: 2015-03-06T02:50:47Z
       
  • Seismic active earth pressure of cohesive-frictional soil on retaining
           wall based on a slice analysis method
    • Abstract: Publication date: March 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 70
      Author(s): Yu-liang Lin , Wu-ming Leng , Guo-lin Yang , Lian-heng Zhao , Liang Li , Jun-sheng Yang
      The M–O (Mononobe–Okabe) theory is used as a standard method to determine the seismic earth pressure. However, the M–O theory does not consider the influence of soil cohesion, and it cannot determine the nonlinear distribution of the seismic earth pressure. This paper presents a general solution for the nonlinear distribution of the seismic active earth pressure of cohesive-frictional soil using the slice analysis method. A new method is proposed to determine the critical failure angle of the backfill wedge under complex conditions, and an iterative calculation method is presented to determine the tension crack depth of the seismic active earth pressure. The considered parameters in the proposed method include the horizontal and vertical seismic coefficients, wall inclination angle, backfill inclination angle, soil friction angle, wall friction angle, soil cohesion, wall adhesion and uniform surcharge. The classical methods of the M–O and Rankine theories can be regarded as special cases of the proposed method. Furthermore, the proposed method is compared with the test results and previously existing solutions to validate the correctness of the results. Additionally, the parameters׳ effect on the critical failure angle, the resultant force, the application-point position, the tension crack depth and the nonlinear distribution of seismic active earth pressure are studied in graphical form.


      PubDate: 2015-03-06T02:50:47Z
       
  • Evaluation of codified elastic design spectrum models for regions of
           low-to-moderate seismicity
    • Abstract: Publication date: March 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 70
      Author(s): Hing-Ho Tsang
      Design spectrum (DS) model is typically specified in a seismic code of practice for structural design. In a region of low-to-moderate seismicity where seismic code does not exist, a DS model in a well established code of practice is usually adopted, while the suitability of such model has seldom been evaluated. In this article, the elastic DS models for reference (rock) site stipulated in six major codes of practice (AS1170.4–2007, EN1998-1:2004, GB50011–2010, IBC–2012, NBCC–2010 and NZS1170.5:2004) have been compared and scrutinized. Three cities of low-to-moderate seismicity, namely, Melbourne (Australia), Hong Kong (China) and Karlsruhe (Germany), have been selected for illustrative purposes. Particular emphasis has been put on the parameterization scheme for DS model. It is found that huge discrepancies (over 100%) exist among the models, especially at the long period range, due to differences in spectral shapes and the recommended corner periods, which would lead to undesirable effects on the use of the displacement-based seismic design approach. It is urged that the values of corner periods should be determined specifically and cautiously based on the regional seismicity pattern and local geological conditions.


      PubDate: 2015-03-06T02:50:47Z
       
  • A micromechanical analysis of the effect of fabric on low-strain stiffness
           of granular soils
    • Abstract: Publication date: March 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 70
      Author(s): Mourad Zeghal , Chrysovalantis Tsigginos
      The effect of fabric on low-strain shear stiffness properties of granular soils was assessed using Discrete Element simulations. These soils were idealized as a collection of non-spherical particles that interact according to Hertz׳s contact law. Different fabrics of the same soil were obtained by extracting particles from the weak or strong interparticle force networks. The associated stiffness properties were evaluated for various levels of isotropic triaxial confining stress conditions. The conducted analyses showed that a soil with a given void ratio and level of confining stress may have various fabrics associated with noticeably different low-strain shear moduli. The mechanical coordination number and particle shape were found to be the main factors that dictate the low-strain stiffness properties of a certain granular soil (with a specific contact law). For a defined level of confining stress, the shear stiffness of a particular soil is shown to be linked to the mechanical coordination number by a unique relation.


      PubDate: 2015-03-06T02:50:47Z
       
  • Inelastic seismic spectra including a damage criterion: A stochastic
           approach
    • Abstract: Publication date: March 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 70
      Author(s): Rita Greco , Giuseppe Carlo Marano
      In this paper, a stochastic approach for obtaining damage-based inelastic seismic spectra is proposed. The Park and Ang damage model, which includes displacement ductility and hysteretic energy, is adopted to take into account the cumulative damage phenomenon in structural systems under strong ground motions. Differently from previous studies in this field, damage-based seismic spectra are obtained by means of peak theory of stochastic processes. The following stochastic inelastic seismic spectra are constructed and then analyzed: damage-based displacement and acceleration inelastic spectra, damage-based response modification factor spectra, damage-based yield strength demand spectra and damage-based inelastic displacement ratio spectra.


      PubDate: 2015-03-06T02:50:47Z
       
  • Shaking-table tests and numerical simulations on a subway structure in
           soft soil
    • Abstract: Publication date: Available online 19 February 2015
      Source:Soil Dynamics and Earthquake Engineering
      Author(s): Chen Guoxing , Chen Su , Zuo Xi , Du Xiuli , QI Chengzhi , Wang Zhihua
      Shaking table tests were performed to investigate the damage mechanisms of a subway structure in soft soil while experiencing strong ground motions. The seismic responses of the structure and soil were found to be more sensitive to input motions with richer low-frequency components. The excess pore pressure ratio of soil increased slightly, and the distribution of the excess pore pressure surrounding the structure showed clear spatial effects. The frequency spectrum characteristics of input ground motions clearly influenced the lateral displacement of the structure. In addition, the structure was most severely damaged at the top or the bottom of the interior columns. Finite element analyses were conducted by using the modified Martin–Seed–Davidenkov viscoelastic and the rate-independent plastic-damage constitutive models for soil and concrete, respectively. Satisfactory agreement was observed between the simulation and test results, the difference between these results was discussed in detail. The results provide insight into how the characteristics of strong ground motion might influence and present a simplified analysis method to quantitatively evaluate the damage of subway structures in soft soil.


      PubDate: 2015-03-06T02:50:47Z
       
  • Seismic dynamics of offshore breakwater on liquefiable seabed foundation
    • Abstract: Publication date: Available online 18 February 2015
      Source:Soil Dynamics and Earthquake Engineering
      Author(s): Jianhong Ye , Gang Wang
      Offshore structures, such as composite breakwaters, are generally vulnerable to strong seismic wave propagating through loose or medium-dense seabed foundation. However, the seismically induced failure process of offshore structures is not well understood. In this study, seismic dynamics of a composite breakwater on liquefiable seabed foundation is investigated using a fully coupled numerical model FSSI-CAS 2D. The computation results show that the numerical model is capable of capturing a variety of nonlinear interaction phenomena between the composite breakwater and its seabed foundation. The numerical investigation demonstrates a three-stage failure process of the breakwater under seismic loading. In this process, the far-field seabed can become fully liquefied first, inducing excessive settlement of the structure, followed by significant lateral movement and tilting of the structure when the near-field soil progressively liquefies. The study demonstrates great promise of using advanced numerical analysis in geotechnical earthquake design of offshore structures.


      PubDate: 2015-03-06T02:50:47Z
       
  • Seasonal differences in seismic responses of embankment on a sloping
           ground in permafrost regions
    • Abstract: Publication date: Available online 13 February 2015
      Source:Soil Dynamics and Earthquake Engineering
      Author(s): Shuangyang Li , Yuanming Lai , Mingyi Zhang , Wenbing Yu
      Because of its direct influence on the amount of unfrozen water and on the strength of intergranular ice in a frozen soil, temperature has a significant effect on all aspects of the mechanical behavior of the active layer in which temperature fluctuates above and below 0°C. Hence seismic responses of engineering structures such as embankment on a sloping ground in permafrost regions exhibit obvious differences with seasonal alternation. To explore the distinctive seismic characteristics of a railway embankment on the sloping ground in permafrost regions, a coupled water-heat-dynamics model is built based on theories of heat transfer, soil moisture dynamics, frozen soil mechanics, soil dynamics, and so on. A well-monitored railway embankment on a sloping ground in Qinghai–Tibet Plateau is taken as an example to simulate seismic responses in four typical seasons in the 25th service year. The numerical results show that seismic acceleration, velocity and displacement responses are significantly different in four typical seasons, and the responses on October 15 are much higher among the four seasons. When the earthquake is over, there are still permanent differential deformations in the embankment and even severe damages on the left slope on October 15. Therefore, this position should be monitored closely and repaired timely to ensure safe operation. In addition, the numerical model and results may be a reference for maintenance, design and study on other embankments in permafrost regions.


      PubDate: 2015-03-06T02:50:47Z
       
  • Response to the discussion on “Recommendations for extension and
           re-calibration of an existing sand constitutive model taking into account
           varying non-plastic fines content” by Md. Mizanur Rahman, S. R. Lo
    • Abstract: Publication date: Available online 10 February 2015
      Source:Soil Dynamics and Earthquake Engineering
      Author(s): Ali Lashkari



      PubDate: 2015-03-06T02:50:47Z
       
  • Editorial Board / Aims and Scope
    • Abstract: Publication date: February 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 69




      PubDate: 2015-03-06T02:50:47Z
       
 
 
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