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EARTH SCIENCES (471 journals)

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Journal Cover Soil Dynamics and Earthquake Engineering
  [SJR: 1.516]   [H-I: 56]   [13 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0267-7261
   Published by Elsevier Homepage  [3040 journals]
  • Experimental study on effect of fly ash on liquefaction resistance of sand
    • Authors: Mahdi Keramatikerman; Amin Chegenizadeh; Hamid Nikraz
      Pages: 1 - 6
      Abstract: Publication date: February 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 93
      Author(s): Mahdi Keramatikerman, Amin Chegenizadeh, Hamid Nikraz
      A series of cyclic triaxial tests were performed to determine the liquefaction resistance of sand stabilised with fly ash (FA). In order to understand the cyclic behaviour of the FA stabilised sand, the effect of relative density (Dr), FA content, confining pressure (CP) and curing time liquefaction resistance were considered. In the first stage of the laboratory tests, specimens of sand mixed with 2% FA under 50 kPa CP and 0.2 CSR with relative density of 20%, 40%, 60%, and 80%, were tested and compared with untreated soil. The results indicated that mixtures of sand-FA in all relative densities have more resistance to liquefaction failure in comparison with untreated soil, and mixture of sand-FA for relative density of 80% has the greatest resistance value. In the second stage, two types of sand-FA mixture (i.e., 4% and 6% FA) with a relative density of 20% under three ranges of confining pressure, namely 50, 70 and 90 kPa, were tested. The results in this stage suggested that the addition of 6% FA to the sand led to an increase in the cyclic response of the soil to the liquefaction in comparison with the specimens of sand mixed with 4% FA in all tested confining pressures. In the last part of the study, variation of the CSR with the number of cycles to liquefaction for a mixture of sand and 2% FA with 20% relative density under 50, 70 and 90 kPa confining pressure were presented and results indicated that the specimens under greater CP liquefied at earlier cycle numbers and vice versa. In continuing to investigate the effect of curing time, the specimens containing 2% FA were cured for 14 and 28 days and tested under 50 kPa CP and 20% relative density. The result showed that an increase in curing time led to an increase in the liquefaction strength of the sand containing FA.

      PubDate: 2016-12-05T10:20:58Z
      DOI: 10.1016/j.soildyn.2016.11.012
      Issue No: Vol. 93 (2016)
       
  • Harmonic response of layered halfspace using reduced finite element model
           with perfectly-matched layer boundaries
    • Authors: Simon Jones
      Pages: 1 - 8
      Abstract: Publication date: January 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 92
      Author(s): Simon Jones
      The current paper investigates the use of perfectly-matched layers (PML) as absorbing elements for a finite element (FE) model simulating a semi-infinite medium. Due to the formulation of the FE-PML model, it is also possible to use a Craig-Bampton reduction to significantly reduce the number of degrees-of-freedom in the model, in an attempt to improve the computational efficiency of the simulation. The perfectly-matched layers use a complex-valued function to numerically stretch the apparent size of PML elements while allowing them to remain nominally small. The results from this investigation suggest the PML elements worked seamlessly with the FE elements to approximate the elastodynamic response of a 3D halfspace subjected to a surface load; the wave energy is completely absorbed by the PMLs regardless of incident angle or wavelength. Furthermore, the size of the model was reduced by approximately 32% using a Craig-Bampton reduction (CBR). The CBR transforms the system into a mixed set of coordinates, including both modal and spatial coordinates. The model reduction is accomplished by neglecting modal frequencies for the system above two and a half times the maximum forcing frequency of interest. By only transforming the frequency-independent FE section into modal coordinates, and leaving the frequency-dependent PML elements as spatial degrees-of-freedom, the mode-shapes must only be solved once and can then be reused for different forcing frequencies. The results from this investigation suggest this could provide computational benefits if a number of cases are being computed for different frequencies.

      PubDate: 2016-10-23T18:06:44Z
      DOI: 10.1016/j.soildyn.2016.08.023
      Issue No: Vol. 92 (2016)
       
  • Studying the uncertainties in the seismic risk assessment at urban scale
           applying the Capacity Spectrum Method: The case of Thessaloniki
    • Authors: Evi Riga; Anna Karatzetzou; Aikaterini Mara; Kyriazis Pitilakis
      Pages: 9 - 24
      Abstract: Publication date: January 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 92
      Author(s): Evi Riga, Anna Karatzetzou, Aikaterini Mara, Kyriazis Pitilakis
      Seismic risk assessment and loss estimation are of major importance for decision-making with respect to the reduction of earthquake-induced losses in large urban areas. However, the methodological chain of seismic risk assessment, from seismic hazard assessment to evaluation of potential losses, encompasses numerous uncertainties, both aleatory and epistemic, associated with different sources. The present study is a comprehensive application of the Capacity Spectrum Method to the seismic risk assessment of the city of Thessaloniki, aiming to give an insight into epistemic uncertainties involved in the above methodology, owing to hazard modelling, structural capacity, fragility and damping, as well as shaking duration. To quantify and discuss the uncertainties, a logic tree approach is used. A sensitivity analysis of the computed seismic risk results is performed to determine the input parameters having the greatest impact. The analyses were carried out for the building stock of the city of Thessaloniki, Greece, for which detailed building inventory and very good knowledge of the soil conditions are available. Only physical losses due to the structural damage of the building stock were considered. Considerable scatter in the risk estimates was observed due to epistemic uncertainties. The sensitivity analyses demonstrated that the most influencing parameters when applying the Capacity Spectrum Method are the selection of the fragility curves for the buildings and the seismic hazard model adopted in the analysis. The decision-making process with respect to seismic risk assessment should therefore carefully account for uncertainties and pay attention to the most influencing parameters regardless of the methodology used.

      PubDate: 2016-10-23T18:06:44Z
      DOI: 10.1016/j.soildyn.2016.09.043
      Issue No: Vol. 92 (2016)
       
  • Efficient model updating of a multi-story frame and its foundation
           stiffness from earthquake records using a timoshenko beam model
    • Authors: E. Taciroglu; S.F. Ghahari; F. Abazarsa
      Pages: 25 - 35
      Abstract: Publication date: January 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 92
      Author(s): E. Taciroglu, S.F. Ghahari, F. Abazarsa
      We present a new approach to estimate the dynamic stiffnesses of soil-foundation systems using earthquake-induced response signals recorded on multi-story buildings with sparsely instrumentation. Identification of soil-foundation dynamic stiffness parameters from real-life data, especially earthquake-induced response signals, is arguably one of the most challenging problems in structural/geotechnical earthquake engineering. This is because the said parameters are frequency-dependent, and the non-stationary input excitation is not measurable due to soil-structure interaction effects. It is possible to identify these parameters using recently developed blind source separation techniques, provided that a finite element model of the superstructure is available. However, developing and updating a finite element model is usually a laborious undertaking, and its success strongly depends on the spatial density of measurements. In the present study, we offer a new method that is based on the use of a Timoshenko beam model to represent the superstructure. In this method, key parameters of the Timoshenko beam model – and those of its soil-foundation system – are adjusted through a systematic procedure, until the systems’ overall (flexible-based) modal properties match those identified from real-life data. The proposed method is robust against sensor sparseness, and yields accurate results even if the foundation rocking is not measured. The proposed procedure is first verified using a synthetic problem, and subsequently applied to real-life data recorded at the Millikan Library building, which is located at the Caltech campus in Pasadena, California.

      PubDate: 2016-10-23T18:06:44Z
      DOI: 10.1016/j.soildyn.2016.09.041
      Issue No: Vol. 92 (2016)
       
  • A design spectrum model for flexible soil sites in regions of
           low-to-moderate seismicity
    • Authors: H.H. Tsang; J.L. Wilson; N.T.K. Lam; R.K.L. Su
      Pages: 36 - 45
      Abstract: Publication date: January 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 92
      Author(s): H.H. Tsang, J.L. Wilson, N.T.K. Lam, R.K.L. Su
      Design spectrum (DS) models in major codes of practice for structural design of buildings typically stipulate empirical site factors for each of the five, or six, site classes. Although the phenomenon of resonant like amplification behaviour of the structure caused by multiple wave reflections is well known, the potentials for such periodic amplification behaviour are not explicitly considered in code models. This is partly because of expert opinion that such effects are very “localised” in the frequency domain and can be suppressed readily by damping. However, investigations into the risk of collapse of non-ductile, and irregular structural systems, common in regions of low-to-moderate seismicity, revealed the extensive influence of periodic base excitations on flexible soil sites (with initial small-strain natural period T i >0.5s). In this paper, an alternative DS model which addresses the important phenomenon of soil resonance without the need of computational site response analysis of the subsurface model of the site is introduced.

      PubDate: 2016-10-23T18:06:44Z
      DOI: 10.1016/j.soildyn.2016.09.035
      Issue No: Vol. 92 (2016)
       
  • An experimental study of high strain-rate properties of clay under high
           consolidation stress
    • Authors: Renshu Yang; Jun Chen; Liyun Yang; Shizheng Fang; Ju Liu
      Pages: 46 - 51
      Abstract: Publication date: January 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 92
      Author(s): Renshu Yang, Jun Chen, Liyun Yang, Shizheng Fang, Ju Liu
      A split Hopkinson pressure bar (SHPB) combined with high pressure consolidation apparatus and high speed camera was used to obtain dynamic compressive stress-strain curves of clay whose over consolidation stress state in the process of formation was properly considered. The stress-strain relationship at various high strain rates from 60s−1 to 600s−1 was obtained. The strain rate and degree of consolidation effects on the compressive response of the consolidated clay were determined. The results show that the dynamic mechanical properties of clay in high pressure consolidation is sensitive to strain rate, and parameters like dynamic strength, failure strain and so on are significantly improved compared with unconsolidated clay which indicate that the initial stress history of the soil materials is also one of the most important factors that affect the dynamic mechanical response.

      PubDate: 2016-10-23T18:06:44Z
      DOI: 10.1016/j.soildyn.2016.09.036
      Issue No: Vol. 92 (2016)
       
  • Soil-structure interaction effects in single bridge piers founded on
           inclined pile groups
    • Authors: Sandro Carbonari; Michele Morici; Francesca Dezi; Fabrizio Gara; Graziano Leoni
      Pages: 52 - 67
      Abstract: Publication date: January 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 92
      Author(s): Sandro Carbonari, Michele Morici, Francesca Dezi, Fabrizio Gara, Graziano Leoni
      This paper investigates the seismic response of bridge piers founded on inclined pile groups in different soil deposits, evaluating effects of soil-structure interaction induced by different pile group geometries and piles inclinations. Analyses are performed in the frequency domain by means of the direct approach taking advantage of a numerical model developed by the authors for the analysis of inclined pile groups. Both the superstructure and piles are modelled with beam elements and the soil is schematized as a visco-elastic medium constituted by independent infinite horizontal layers. The soil-pile and the pile-soil-pile interaction are captured in the frequency domain by means of elastodynamic Green's functions that also allow including the hysteretic and radiation damping. The significance of kinematic stress resultants in piles, the foundation filtering effect and the rotational component of the input motion due to the coupled roto-translational behaviour of the soil-foundation system are also investigated; to this purpose kinematic interaction analyses are performed. These analyses revealed essential for the understanding of the general phenomena governing the dynamic response of the whole soil-foundation-superstructure systems. Results of numerical investigations highlight that conventional design approaches suggested by codes do not provide reliable predictions of the superstructure displacements and stress resultants.

      PubDate: 2016-10-23T18:06:44Z
      DOI: 10.1016/j.soildyn.2016.10.005
      Issue No: Vol. 92 (2016)
       
  • Flow deformation and cyclic resistance of saturated loose sand considering
           initial static shear effect
    • Authors: Z.X. Yang; K. Pan
      Pages: 68 - 78
      Abstract: Publication date: January 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 92
      Author(s): Z.X. Yang, K. Pan
      In practical engineering, a driving stress often exists and acts on the soil elements, and this stress may have a significant effect on the deformational characteristics and liquefaction resistance of sand when the sand is subjected to seismic loadings. This paper presents a systematic experimental investigation into the undrained cyclic behavior of saturated loose sand with the static shear under both triaxial compression and extension conditions. Various combinations of the magnitude of static stresses and cyclic stresses were considered in the triaxial tests. The results indicate that different static shear stress conditions lead to two distinct failure modes, namely, flow liquefaction and residual deformation failure. The required number of loading cycles for the onset of flow deformation and failure are both related to two stress parameters, i.e., cyclic stress ratio (CSR) and static stress ratio (SSR). In viewing the failure envelope established against the two stress variables CSR and SSR, a critical SSR that identifies the role of the presence of initial static shear stress is obtained: when SSR is less than that critical value, the resistance may increase, whereas the resistance may decrease as SSR becomes larger. In addition, the triggering conditions of flow deformation under cyclic loading can be interpreted with the instability response of sand under monotonic loading. Combined with the observation on the cyclic deviatoric strains developed during and after the flow deformation, a unified interpretation is made to quantify the effects of both the SSR and CSR on the cyclic resistance of loose sand.

      PubDate: 2016-10-23T18:06:44Z
      DOI: 10.1016/j.soildyn.2016.09.002
      Issue No: Vol. 92 (2016)
       
  • Evaluation of power substation equipment seismic vulnerability by
           multivariate fragility analysis: A case study on a 420kV circuit breaker
    • Authors: Seyed Alireza Zareei; Mahmood Hosseini; Mohsen Ghafory-Ashtiany
      Pages: 79 - 94
      Abstract: Publication date: January 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 92
      Author(s): Seyed Alireza Zareei, Mahmood Hosseini, Mohsen Ghafory-Ashtiany
      Recent earthquakes have shown that Electrical Power Substations apparatuses are seismically vulnerable. This causes to disrupt the power supply in many cases, and therefore their seismic evaluation with high reliability is significantly important. Using fragility curves is a common practice for assessing seismic vulnerability. In general, fragility curves are based on only one intensity measure (IM), such as peak ground acceleration (PGA). This study has attempted to propose multivariate fragility analysis. One of the major advantages of this developed multivariate fragility analysis is to more reliably determine the seismic vulnerability of a region. A 420kV circuit breaker (CB) was modeled and analyzed by using finite element technique. The results show that by adding another IM as peak ground velocity (PGV) the dispersion of the created data decreases to a great extent and therefore, the developed fragility surfaces helps conducting the seismic risk evaluation of electric power system components with higher level of reliability. Based on the obtained numerical results it can be expressed that for moderate damage state the fragility values are not much dependent on the PGV variation, while for severe damage state the dependence of fragility values on PGV is noticeable, particularly for PGA values in range of 0.1–0.7g.

      PubDate: 2016-10-23T18:06:44Z
      DOI: 10.1016/j.soildyn.2016.09.026
      Issue No: Vol. 92 (2016)
       
  • A modal shear-based pushover procedure for estimating the seismic demands
           of tall building structures
    • Authors: Mohammad Hossein Vafaee; Hamed Saffari
      Pages: 95 - 108
      Abstract: Publication date: January 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 92
      Author(s): Mohammad Hossein Vafaee, Hamed Saffari
      Non-linear static procedure (NSP) has been considered as a popular method to predict seismic force and deformation demands for performance evaluation of the structures, in recent years. However, this evaluation tool is restricted to low-rise and regular buildings in which the fundamental vibration mode dominates the structural behavior. Recently, some advanced procedures have been presented to oversee these conventional procedure deficiencies. In the current study, a new nonlinear static procedure considering the effects of higher modes in structural responses is presented. This approach assigns a contribution factor for each mode based on modal shear distribution. The offered contribution factor can be applied for determining the importance of each mode in lateral load pattern formation. In order to verify the results, some other types of pushover-based analysis are also performed and the responses obtained from each NSP are compared with those of rigorous non-linear response history analysis (NL-RHA). Results demonstrated the efficiency of the proposed method in accurate prediction of the seismic demands of high-rise buildings.

      PubDate: 2016-10-23T18:06:44Z
      DOI: 10.1016/j.soildyn.2016.09.033
      Issue No: Vol. 92 (2016)
       
  • System identification and modal analysis of an arch dam based on
           earthquake response records
    • Authors: Jian Yang; Feng Jin; Jin-Ting Wang; Li-Hang Kou
      Pages: 109 - 121
      Abstract: Publication date: January 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 92
      Author(s): Jian Yang, Feng Jin, Jin-Ting Wang, Li-Hang Kou
      The true dynamic characteristics of dams, namely, natural frequencies, damping ratios, and mode shapes, are important to earthquake-resistant design. Thus, system identification based on in-site measurements is useful for numerical analysis and health monitoring. The well-instrumented strong motion array on an arch dam in Southwestern China recorded some seismic response data. The dynamic properties of the dam are identified from records of the top five strongest earthquake motions using power spectral density functions, transfer functions, and the ARX model. The identified modal parameters of the different seismic events are compared, and the stability of the stiffness of the dam system from 2002 to 2008 and the nonuniformity in the input ground motion are indicated. A linear finite element model of the dam and a nonlinear model that considers contraction joints are constructed and calibrated to reproduce the frequencies determined from the system identification. The modal analysis highlights potential information about the dynamic characteristics of the dam. The comparison of the results of the system identification and calibration shows that the use of the nonlinear model may be reasonable in simulating the dynamic response of the Ertan Dam.

      PubDate: 2016-10-23T18:06:44Z
      DOI: 10.1016/j.soildyn.2016.09.039
      Issue No: Vol. 92 (2016)
       
  • Design of monopiles for offshore wind turbines in 10 steps
    • Authors: Laszlo Arany; S. Bhattacharya; John Macdonald; S.J. Hogan
      Pages: 126 - 152
      Abstract: Publication date: January 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 92
      Author(s): Laszlo Arany, S. Bhattacharya, John Macdonald, S.J. Hogan
      A simplified design procedure for foundations of offshore wind turbines is often useful as it can provide the types and sizes of foundation required to carry out financial viability analysis of a project and can also be used for tender design. This paper presents a simplified way of carrying out the design of monopiles based on necessary data (i.e. the least amount of data), namely site characteristics (wind speed at reference height, wind turbulence intensity, water depth, wave height and wave period), turbine characteristics (rated power, rated wind speed, rotor diameter, cut-in and cut-out speed, mass of the rotor-nacelle-assembly) and ground profile (soil stiffness variation with depth and soil stiffness at one diameter depth). Other data that may be required for final detailed design are also discussed. A flowchart of the design process is also presented for visualisation of the rather complex multi-disciplinary analysis. Where possible, validation of the proposed method is carried out based on field data and references/guidance are also drawn from codes of practice and certification bodies. The calculation procedures that are required can be easily carried out either through a series of spreadsheets or simple hand calculations. An example problem emulating the design of foundations for London Array wind farm is taken to demonstrate the proposed calculation procedure. The data used for the calculations are obtained from publicly available sources and the example shows that the simplified method arrives at a similar foundation to the one actually used in the project.

      PubDate: 2016-10-23T18:06:44Z
      DOI: 10.1016/j.soildyn.2016.09.024
      Issue No: Vol. 92 (2016)
       
  • Liquefaction assessments at shallow foundation building sites in the
           Central Business District of Christchurch, New Zealand
    • Authors: Jonathan D. Bray; Christopher S. Markham; Misko Cubrinovski
      Pages: 153 - 164
      Abstract: Publication date: January 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 92
      Author(s): Jonathan D. Bray, Christopher S. Markham, Misko Cubrinovski
      The 2010–2011 Canterbury earthquake sequence provides an exceptional opportunity to investigate the effects of varying degrees of liquefaction on the built environment. Significant ground settlements and building damage in the Central Business District (CBD) were observed for the Christchurch earthquake. The results of CPTs and soil index tests from exploratory borings performed in the CBD are combined with cyclic triaxial (CTX) test results to characterize the soil deposits at several buildings sites. Conventional one-dimensional liquefaction-induced ground settlement procedures do not capture shear-induced deformation mechanisms and the effects of ground loss due to sediment ejecta. Improved procedures are required. Nonlinear effective stress analyses using robust soil constitutive models calibrated through CTX tests provide a means for developing these procedures. The CTX tests estimate generally consistent cyclic resistances as the CPT-based methods for medium dense sands and silty sands; however, the CTX tests provide useful insights regarding pore water pressure response and strain development. Correlations and CTX tests performed on loose clean sands indicate that these specimens were disturbed by the sampling process. Interim findings from this ongoing study are presented, and preliminary recommendations for evaluating the seismic performance of buildings with shallow foundations at sites with liquefiable soils are provided.

      PubDate: 2016-10-23T18:06:44Z
      DOI: 10.1016/j.soildyn.2016.09.049
      Issue No: Vol. 92 (2016)
       
  • A model for estimating horizontal aftershock ground motions for active
           crustal regions
    • Authors: Byungmin Kim; Moochul Shin
      Pages: 165 - 175
      Abstract: Publication date: January 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 92
      Author(s): Byungmin Kim, Moochul Shin
      Inconsistent observations on the characteristics of ground motions from aftershocks have been found, while there is increasing attention to effects of aftershock ground motions on structural behaviors. This study examines differences in ground motions from main shock and aftershock earthquakes using the NGA-West2 database, and propose an empirical model to estimate the average horizontal components of peak ground acceleration (PGA), and peak ground velocity (PGV), and 5% damped pseudo spectral acceleration (PSA) at various spectral periods of aftershock earthquakes for tectonically active crustal regions, as a function of aftershock to main shock magnitude ratio, distance ratio, and time-averaged shear-wave velocity in the upper 30m of soil deposits (V S30). Spectral accelerations from aftershock earthquakes are smaller than those from main shock earthquakes given the same magnitude, especially at short periods. Performance of the proposed model is evaluated using a mixed-effects residuals analysis. Period-dependent standard deviation of residuals is also presented.

      PubDate: 2016-10-23T18:06:44Z
      DOI: 10.1016/j.soildyn.2016.09.040
      Issue No: Vol. 92 (2016)
       
  • A fast and accurate method to compute dispersion spectra for layered media
           using a modified Kausel-Roësset stiffness matrix approach
    • Authors: Jyant Kumar; Tarun Naskar
      Pages: 176 - 182
      Abstract: Publication date: January 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 92
      Author(s): Jyant Kumar, Tarun Naskar
      This brief article presents a simple modification to the widely-used Kausel-Roësset Stiffness Matrix Method (SMM), and in particular to its implementation in the context of the Thin-Layer Method (TLM). This modification allows making fast and accurate computations of wavenumber spectra even for layered media underlain by infinitely deep half-spaces. As is well known, the TLM uses a finite element expansion in the depth direction, which in principle disallows exact representations of infinitely deep media other than through Paraxial Approximations or Perfectly Matched Layers. However, with the modification presented herein, that obstacle is removed. The very simple method is first presented and then demonstrated by means of examples involving layered half-spaces.

      PubDate: 2016-10-23T18:06:44Z
      DOI: 10.1016/j.soildyn.2016.09.042
      Issue No: Vol. 92 (2016)
       
  • Effect of ground motion filtering on the dynamic response of a seismically
           isolated bridge with and without fault crossing considerations
    • Authors: Shuo Yang; George P. Mavroeidis; Alper Ucak; Panos Tsopelas
      Pages: 183 - 191
      Abstract: Publication date: January 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 92
      Author(s): Shuo Yang, George P. Mavroeidis, Alper Ucak, Panos Tsopelas
      High-pass filtering not only removes the low-frequency noise from the near-fault ground motion records, but also eliminates the permanent ground displacement and reduces the dynamic ground displacement. This may considerably influence the calculated seismic response of a spatially extended engineering structure crossing a fault rupture zone. To demonstrate the importance of incorporating permanent ground displacements in the analysis and design of extended structures under specific fault crossing conditions, the dynamic response of a seismically isolated bridge located in the vicinity of a surface fault rupture (“Case A”) or crossing a fault rupture zone (“Case B”) is calculated by utilizing a near-fault ground motion record processed with and without a displacement offset. The seismically isolated bridge considered in this study is a 10-span continuous structure supported by 11 piers, resembling a typical segment of the 2.3km long Bolu Viaduct 1 located in west-central Turkey. The Lucerne Valley record from the 1992 M w 7.2 Landers earthquake, which preserves a permanent ground displacement in the fault-parallel direction and exhibits a large velocity pulse in the fault-normal direction, is used as the basis for investigating the effect of high-pass filtering on the dynamic response of the bridge. For the seismically isolated bridge located in the vicinity of the surface fault rupture (“Case A”), the utilization of the high-pass filtered ground motion leads to underestimating the demands of pier top, pier bottom and deck displacements. However, the demands of isolation displacement, isolation permanent displacement and pier drift are almost identical for both the unfiltered and filtered versions of the ground motion record. On the other hand, for the seismically isolated bridge traversed by a fault rupture zone (“Case B”), all response quantities are significantly underestimated when the high-pass filtered ground motion is used. These results, though limited to a single bridge structure and a single ground motion input, clearly indicate the importance of permanent ground displacement on the dynamic response of spatially extended engineering structures crossing fault rupture zones.

      PubDate: 2016-10-23T18:06:44Z
      DOI: 10.1016/j.soildyn.2016.10.001
      Issue No: Vol. 92 (2016)
       
  • Modal and nodal impedance functions for truncated semi-infinite soil
           domains
    • Authors: E. Esmaeilzadeh Seylabi; C. Jeong; E. Taciroglu
      Pages: 192 - 202
      Abstract: Publication date: January 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 92
      Author(s): E. Esmaeilzadeh Seylabi, C. Jeong, E. Taciroglu
      A general methodology for numerically extracting the impedance functions of flexible soil-foundation interfaces (SFIs) in both physical (nodal) and modal domains is provided, which can also be applied to any truncated semi-infinite elastic media. A recently developed finite element method that features perfectly matched layers as absorbing boundary conditions is used to compute the wave responses within the semi-infinite soil domain. Using this tool, the impedance functions are obtained by prescribing the known nodal or modal displacement along the SFI and computing the corresponding reactions. The modal approach has the advantage of only computing the impedance functions for the most important mode shapes that control the behavior of the interface with a reduced computational cost. The accuracy of the proposed method is investigated through forced-vibration analysis of a strip foundation on surface of an elastic half-space. It is found that reduced-order modal impedance matrices can be as accurate as their nodal counterparts as long as a set of appropriate mode shapes is retained. Moreover, depending on the type of the applied loading and its frequency content, higher (flexible) mode shapes will be activated, and therefore, the substructure methods that are based on rigid or winkler-type impedance functions may predict the actual response of the foundation poorly.

      PubDate: 2016-10-23T18:06:44Z
      DOI: 10.1016/j.soildyn.2016.09.037
      Issue No: Vol. 92 (2016)
       
  • Ductility demands of MRF structures on soft soils considering
           soil-structure interaction
    • Authors: M. Ghandil; F. Behnamfar
      Pages: 203 - 214
      Abstract: Publication date: January 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 92
      Author(s): M. Ghandil, F. Behnamfar
      The problem of nonlinear response of moment resisting frames on nonlinear soft soils is investigated. The soil-structure interaction (SSI) is considered using the direct method. The direct method consists of concurrent modeling of structure and its supporting soil to the bedrock. The soil medium is usually modeled using the equivalent linear method where the shear modulus and damping ratio of soil are replaced with values representative of the nonlinear soil behavior. A correction of this method with regard to very large strains of soil at and around foundations is proposed in this study. The nonlinear behavior of the frame elements of structure is assumed to be concentrated at plastic hinges at the ends of members. Drifts, shear forces and ductility demands of stories of the studied buildings are calculated once assuming a rigid base and then a soft supporting soil for the structure with nonlinear time-history analysis. It is shown that SSI increases the drifts and ductility demands of the lower stories. Interim modification factors being ratios of ductility demands with SSI to those without SSI (fixed-base cases) are presented as checking tools for when SSI is important for nonlinear dynamic response calculation of structures.

      PubDate: 2016-10-23T18:06:44Z
      DOI: 10.1016/j.soildyn.2016.09.051
      Issue No: Vol. 92 (2016)
       
  • Identification of soil dynamic properties of sites subjected to
           bi-directional excitation
    • Authors: Vicente Mercado; Waleed El-Sekelly; Mourad Zeghal; Tarek Abdoun
      Pages: 215 - 228
      Abstract: Publication date: January 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 92
      Author(s): Vicente Mercado, Waleed El-Sekelly, Mourad Zeghal, Tarek Abdoun
      Accurate evaluation of soil dynamic properties is essential for seismic response analyses of sites. In a number of studies, site properties have been identified using one-dimensional analyses. Such analyses uncouple the two-dimensional (horizontal) response of soil deposits, which is inherently coupled. This paper presents a system identification technique that takes into account the coupled two-directional response of soil deposits. The technique employs non-parametric estimates of the shear stresses derived from acceleration records provided by a vertical (downhole) array. A multi-yield surface plasticity approach is used to model the multi-dimensional stress-strain relation. The identification technique is first verified using finite elements computational simulations. This technique was then used to assess the coupled response of the Wildlife liquefaction research site (Imperial Valley, California). The identified shear moduli and shear wave velocities were found to be in a very good agreement with those measured in the field using crosshole seismic testing.

      PubDate: 2016-10-23T18:06:44Z
      DOI: 10.1016/j.soildyn.2016.09.038
      Issue No: Vol. 92 (2016)
       
  • A modified dynamic shear modulus model for rockfill materials under a wide
           range of shear strain amplitudes
    • Authors: Wei Zhou; Yuan Chen; Gang Ma; Lifu Yang; Xiaolin Chang
      Pages: 229 - 238
      Abstract: Publication date: January 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 92
      Author(s): Wei Zhou, Yuan Chen, Gang Ma, Lifu Yang, Xiaolin Chang
      High rockfill dams experience a wide range of shear strain amplitudes during earthquakes. To provide more reliable material property descriptions for earthquake response analysis of high rockfill dams, this study investigates the dynamic properties of rockfill materials in a wide strain range by large-scale cyclic triaxial testing with a high-sensitivity laser sensor. The results reveal the considerable increase of shear modulus and decrease of damping ratio with increasing confining pressure for a given initial stress ratio and the significant effect of the initial stress ratio on the small-strain shear modulus and normalized shear modulus. Previously proposed equations were found to imprecisely depict the variation of the dynamic shear modulus of rockfill materials for a wide strain range. Furthermore, the dynamic shear modulus is dependent on the Initial stress ratio in the anisotropic stress condition. Based on the existing hyperbolic model, a modified model for rockfill materials is suggested to accurately estimate the nonlinear behavior. The applicability of the modified model and previous studies for rockfill materials are assessed in the estimation of the normalized shear modulus. The results provide a reference for evaluating the accurate shear modulus in a wide strain range for strong earthquake motions.

      PubDate: 2016-10-30T21:54:39Z
      DOI: 10.1016/j.soildyn.2016.10.027
      Issue No: Vol. 92 (2016)
       
  • 3D integrated numerical model for Fluid-Structures-Seabed Interaction
           (FSSI): Loosely deposited seabed foundation
    • Authors: Jianhong Ye; D.-S. Jeng; A.H.C. Chan; R. Wang; Q.C. Zhu
      Pages: 239 - 252
      Abstract: Publication date: January 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 92
      Author(s): Jianhong Ye, D.-S. Jeng, A.H.C. Chan, R. Wang, Q.C. Zhu
      In the past several decades, a great number of offshore structures have been constructed on loosely deposited seabed foundation because sometimes there would be no a dense seabed floor could be chosen in planned sites, for example, the breakwaters and oil platforms in the Yellow River estunary area, China. Wave-induced residual liquefaction is easy to occur in loosely deposited seabed, which brings great risk to the stability of offshore structures. In this study, we focus our attention on the 3D interaction mechanism between ocean wave, a caisson breakwater and its loosely deposited seabed foundation. A three-dimensional integrated numerical model FSSI-CAS 3D is taken as the computational tool; and the soil constitutive model: Pastor-Zienkiewicz Mark III (PZIII) proposed by Pastor et al. [16] is adopted to describe the wave-induced dynamic behavior of loose seabed soil. The numerical results indicate that the developed integrated numerical model FSSI-CAS 3D is capable of capturing a series of nonlinear phenomena, such as tilting, subsiding of breakwater, as well as residual liquefaction in loose seabed foundation etc., in the interaction process between ocean wave, a caisson breakwater and its loose seabed foundation. The purpose of this study is to provide coastal engineers with comprehensive understanding of FSSI problme involving loosely deposited seabed soil; and propose a reliable computational method to engineers involved in the design of offshore structures on loose seabed foundation.

      PubDate: 2016-11-21T01:52:47Z
      DOI: 10.1016/j.soildyn.2016.10.026
      Issue No: Vol. 92 (2016)
       
  • Optimal Caughey series representation of classical damping matrices
    • Authors: J. Enrique Luco; Armando Lanzi
      Pages: 253 - 265
      Abstract: Publication date: January 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 92
      Author(s): J. Enrique Luco, Armando Lanzi
      A least squares approach to determine the coefficients in a Caughey series representation of a classical damping matrix is presented. Instead of solving an ill-conditioned Vandermonde system of equations involving the modal damping ratios at a set of pivots, the procedure uses a least squares fit between the polynomial representing the damping ratios and the assumed known frequency dependence of the damping ratios. The proposed approach eliminates the large fluctuations of the damping ratios associated with the standard approach. Three alternative procedures are presented: (i) analytical application of the least squares approach for an expansion into power series, (ii) numerical solution of the least squares equations for a dense set of pivots, and (iii) expansion of the damping matrix into series of Legendre polynomials of matrices. In each alternative, the cases of series including or excluding the mass-proportional term are considered separately.

      PubDate: 2016-11-06T22:13:55Z
      DOI: 10.1016/j.soildyn.2016.10.028
      Issue No: Vol. 92 (2016)
       
  • Estimation method for ground deformation of granular soils caused by
           dynamic compaction
    • Authors: Wei Wang; Jin-Jian Chen; Jian-Hua Wang
      Pages: 266 - 278
      Abstract: Publication date: January 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 92
      Author(s): Wei Wang, Jin-Jian Chen, Jian-Hua Wang
      A numerical investigation into the performance of ground deformation due to dynamic compaction (DC), and a developed method of estimating ground deformation of granular soils caused by DC are presented. Firstly, a 2D numerical model is created in LS-DYNA and the result is verified by variables measured in a real field case using DC treatment. A simplified model for describing ground deformation is presented. Five deformation variables, δ v m , d δ v =0 , d δ u m , δ u m , d δ u =0.01% W t H , are defined to describe characteristics of ground surface deformation. An extensive parametric study is then conducted to investigate the effect of each parameter on the five deformation variables. Finally, based on the results obtained, a forecast model is produced to describe ground deformation under DC. The applicability of the proposed procedure is then illustrated by comparing its predictions with a case of DC applied in the field. The results of this comparison indicate that the predictions using the developed method are reasonably realistic. This suggested method can provide some easy and convenient guidelines to determine ground deformation of granular soils due to dynamic compaction.

      PubDate: 2016-11-06T22:13:55Z
      DOI: 10.1016/j.soildyn.2016.09.015
      Issue No: Vol. 92 (2016)
       
  • Dynamic pile impedances for laterally–loaded piles using improved Tajimi
           and Winkler formulations
    • Authors: George Anoyatis; Anne Lemnitzer
      Pages: 279 - 297
      Abstract: Publication date: January 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 92
      Author(s): George Anoyatis, Anne Lemnitzer
      Lateral dynamic soil–pile interaction is investigated through an improved Tajimi type solution. The soil is treated as a continuum with hysteretic material damping as previously proposed by the authors, and the pile is modelled as beam using traditional strength-of-materials solutions. Following the pioneering work of Novak and Nogami, a more accurate analytical model for the static and harmonic response of a pile in a soil layer overlying rock is proposed, and closed form expressions for pile head stiffness are derived. Results are validated through comparisons against rigorous solutions from literature. Hereafter, the Winkler model was considered as a simple alternative for predicting pile head stiffness and damping. An extensive review of available Winkler moduli demonstrated that the Winkler model performance strongly depends on the selection of the respective moduli but found to be satisfactory in static conditions. Most existing expressions for dynamic Winkler moduli were found to render the model incapable of capturing resonant effects. Consequently, a new expression for a dynamic Winkler modulus is derived based on a modification of the classic dynamic plane strain modulus of Baranov–Novak. Implemented in the Winkler model this expression is capable of accurately computing dynamic stiffness attenuation and damping increase for frequencies up to the first resonance over a wide range of pile slenderness ratios.

      PubDate: 2016-11-06T22:13:55Z
      DOI: 10.1016/j.soildyn.2016.09.020
      Issue No: Vol. 92 (2016)
       
  • Damage-based strength reduction factor for nonlinear structures subjected
           to sequence-type ground motions
    • Authors: Yongqun Zhang; Jun Chen; Chaoxu Sun
      Pages: 298 - 311
      Abstract: Publication date: January 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 92
      Author(s): Yongqun Zhang, Jun Chen, Chaoxu Sun
      This paper investigates the strength reduction factor of single-degree-of-freedom (SDOF) system subjected to the mainshock–aftershock sequence-type ground motions. Both displacement ductility and cumulative damage are considered in the reduction factor. Records of mainshock-aftershock earthquakes were collected and classified according to site properties. The aftershock ground motions in sequence are scaled to five relative intensity levels. Based on the nonlinear time-history analysis of inelastic SDOF systems, the effects of natural period, ductility factor, damage index and aftershock have been studied statistically. The results indicate that the aftershock ground motion has significant influences on strength reduction factors, and the damage-based strength reduction factor is about 0.6–0.9 times of the ductility-based strength reduction factor. Finally, an empirical expression for strength reduction factor was established by regression analysis.

      PubDate: 2016-11-06T22:13:55Z
      DOI: 10.1016/j.soildyn.2016.10.002
      Issue No: Vol. 92 (2016)
       
  • A study on a MR damping system with lumped mass for a two-span bridge to
           diminish its earthquake-induced longitudinal vibration
    • Authors: G. Heo; C. Kim; S. Jeon; C. Lee; S. Seo
      Pages: 312 - 329
      Abstract: Publication date: January 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 92
      Author(s): G. Heo, C. Kim, S. Jeon, C. Lee, S. Seo
      This paper examines the effectiveness of a MR damping system with lumped mass for a longitudinal vibration control of two-span bridge, preventing spans from pounding each other and mitigating its seismic responses when earthquake-induced load is inflicted. The MR damping system with lumped mass proposed in this study it was constituted by three components: a MR damper (30kN) which connected two spans of a bridge and two spans themselves made different mass and stiffness. Its function was designed to impose an effective check on relative displacement and pounding. In order to prove its effectiveness, a two-span bridge (8.3m long) was constructed with a MR damper installed beneath the two spans. First, a mathematical model of the bridge was derived; also, a model of the MR damper was verified through a separate test on its performance. Next, shaking table tests were carried out by inflicting 150% of El-centro earthquake and 60% of Kobe earthquake to see how effective the system would be in mitigating seismic responses. All the tests were done under various conditions (un-control, passive off, passive on, Lyapunov control, and Clipped-optional control) in order to closely examine and analyze under which condition mitigation could be maximized and how mitigation could be effected. As a result of the tests, it was found that the MR damping system with lumped mass was effective in preventing two spans from pounding each other and its active performance decreased the relative displacement of the bridge structure. Therefore, it was proven to be effective in attenuating the seismic responses of two-span bridge in longitudinal direction.

      PubDate: 2016-11-06T22:13:55Z
      DOI: 10.1016/j.soildyn.2016.10.004
      Issue No: Vol. 92 (2016)
       
  • Determination of seismic compression of sand subjected to two horizontal
           components of earthquake ground motions
    • Authors: Chun-Xiao Nie; Qing-Sheng Chen; Guang-Yun Gao; Jun Yang
      Pages: 330 - 333
      Abstract: Publication date: January 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 92
      Author(s): Chun-Xiao Nie, Qing-Sheng Chen, Guang-Yun Gao, Jun Yang
      The objective of this Technical Note is to investigate the ratio of seismic compression of sand subjected to two mutually perpendicular horizontal components of earthquake ground motions simultaneously to its counterpart for single component of horizontal motions. By using a verified, fully coupled and inelastic finite element procedure, sand specimens with various relative densities (Dr=45%, 60% and 100%) are subjected to each of the horizontal components of motion separately, and then simultaneously, with the vertical strains and corresponding ratio computed for each case. In total, 296 shallow crustal horizontal motions (i.e. 148 sets of horizontal motions) with various earthquake magnitudes, site to source distances, durations, and site conditions recorded in active tectonic regions are used in the analyses. The results showed that the ratio generally ranges from 1.52 to 2.32, and it increases with earthquake magnitude and relative density of sand but decreases with epicentral distance. These results can be used in conjunction with seismic compression correlations for single component of motion to estimate its counterpart for multiple components of motion, thereby increasing the accuracy in predicting the severity of seismic compression under multi-directional seismic motions.

      PubDate: 2016-11-06T22:13:55Z
      DOI: 10.1016/j.soildyn.2016.10.007
      Issue No: Vol. 92 (2016)
       
  • Local amplification and subsoil structure at a difficult site:
           Understanding site effects from different measurements
    • Authors: Francisco J. Chávez-García; Dimitris Raptakis
      Pages: 334 - 344
      Abstract: Publication date: January 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 92
      Author(s): Francisco J. Chávez-García, Dimitris Raptakis
      We present a detailed site effects study at a site (TYF) close to the Thermaikos gulf coast in Thessaloniki, northern Greece. Different types of data recorded by different instruments are analyzed. Empirical amplification is estimated using spectral ratios relative to a reference station (SSR) and horizontal to vertical spectral ratios (HVSR) using earthquake data. In addition, seismic noise records from different arrays were analyzed using HVSR. Our results show that earthquake data SSR fails for our data. The reason is the poor signal to noise ratio of our records. Better results were obtained using HVSR for earthquake data. Seismic noise HVSR were not useful due to the particular soil profile at TYF, with the exception of HVSR of seismic noise recorded in one of our arrays that were able to reflect a significant change in the coast line at our site. Although amplification at site TYF is relatively small, it is large enough to originate a difference of one intensity unit relative to firm ground motion. Amplification at TYF is caused by a deep soil structure (over 350m in depth) and therefore cannot be captured using measures like Vs30.

      PubDate: 2016-11-06T22:13:55Z
      DOI: 10.1016/j.soildyn.2016.10.008
      Issue No: Vol. 92 (2016)
       
  • Evaluation of the seismic earth pressure for inverted T-shape stiff
           retaining wall in cohesionless soils via dynamic centrifuge
    • Authors: Seong-Bae Jo; Jeong-Gon Ha; Jin-Sun Lee; Dong-Soo Kim
      Pages: 345 - 357
      Abstract: Publication date: January 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 92
      Author(s): Seong-Bae Jo, Jeong-Gon Ha, Jin-Sun Lee, Dong-Soo Kim
      In the design procedure of a retaining wall, the pseudo-static method has been extensively used and the dynamic earth pressure has been calculated based on force equilibrium using the Mononobe–Okabe method that is an extension of the Coulomb's earth pressure theory. According to the Mononobe–Okabe method, the resultant total dynamic thrust would act at a height of 0.33H. The Seed and Whitman method that is a modification of the Mononobe–Okabe method, suggests that the dynamic thrust would be applied at 0.6H above the base. There is no clear empirical basis for the distribution of the dynamic earth pressure, and recent experimental research studies have shown that the dynamic earth pressure has a triangular shape, and that the dynamic thrust is applied at 0.33H above the base. Moreover, pseudo-static methods do not consider the effects of the inertial force of the wall itself on the structural behavior. Two dynamic centrifuge tests were designed and conducted to evaluate the magnitude and distribution of the dynamic earth pressure and the inertial effect of the wall itself on an inverted, T-shape, stiff retaining wall with a dry medium sand backfill. Results from two sets of dynamic centrifuge experiments show that the dynamic earth pressure has a triangular shape for critical states during the earthquake, and that the inertial force of the wall significantly influences the structural moment. Moreover, the deformation pattern, the rigidity of the retaining wall, and the frequency contents of the input motions cause the phase difference between the wall and the soil. Correspondingly, this phase difference influences the dynamic earth pressure.

      PubDate: 2016-11-06T22:13:55Z
      DOI: 10.1016/j.soildyn.2016.10.009
      Issue No: Vol. 92 (2016)
       
  • Recorded seismic response of the Samoa Channel Bridge-foundation system
           and adjacent downhole array
    • Authors: Ning Wang; Ahmed Elgamal; Thomas Shantz
      Pages: 358 - 376
      Abstract: Publication date: January 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 92
      Author(s): Ning Wang, Ahmed Elgamal, Thomas Shantz
      A large set of earthquake records from the highly instrumented Samoa Channel bridge-ground system has been compiled and made available by the California Geological Survey. During six seismic events, more than 30 data channels have been documenting the seismic response of the bridge, abutments, and adjacent ground surface. Of special interest is the response of one of the bridge piers with records at the deck level, pile cap and within the underlying pile foundation. Response of this pile foundation is compared to that of the ground as documented by the nearby Eureka geotechnical downhole array. In this paper, records from the strongest to date 2010 Ferndale earthquake (PGA of about 0.16g), along with other available low-amplitude events (2007–2014) are employed to evaluate the ground, pile foundation, and overall bridge seismic response. Spatial variation of the recorded motions is examined. Linear and nonlinear response of the ground and the bridge are assessed using system identification techniques. During the strong shaking phase of the 2010 Ferndale Earthquake, a clear and significant stiffness reduction was observed in the column as well as in the foundation of the instrumented pier.

      PubDate: 2016-11-06T22:13:55Z
      DOI: 10.1016/j.soildyn.2016.09.034
      Issue No: Vol. 92 (2016)
       
  • Numerical modelling method for inelastic and frequency-dependent behavior
           of shallow foundations
    • Authors: Seok hyeon Chai; Amir Reza Ghaemmaghami; Oh-Sung Kwon
      Pages: 377 - 387
      Abstract: Publication date: January 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 92
      Author(s): Seok hyeon Chai, Amir Reza Ghaemmaghami, Oh-Sung Kwon
      This paper presents a novel framework with which the inelastic behavior and the frequency-dependent dynamic characteristics of soil-foundation system can be represented with a computationally efficient numerical model. The inelastic behavior of soil in the vicinity of a shallow foundation is represented with a macro-element which is based on the classical plasticity theory. The frequency-dependent property of soil-foundation system is represented with a recursive parameter model. The framework allows integration of both models such that both the inelastic behavior and the frequency-dependent characteristics can be captured. The proposed method is verified against FE analysis of a shallow foundation in the two dimensional parametric space of frequency and inelasticity. The verification shows that the model using the proposed framework can fully represent the inelastic cyclic behavior at low frequency excitation and the dynamic response at high frequency excitation. The method provides an approximate solution for the cases in-between, e.g. a foundation subjected large amplitude high-frequency excitation. As an application example, the method is applied to an analysis of a bridge pier subjected to earthquake loading.

      PubDate: 2016-11-06T22:13:55Z
      DOI: 10.1016/j.soildyn.2016.10.030
      Issue No: Vol. 92 (2016)
       
  • Liquefaction characteristics of gravelly soil under cyclic loading with
           constant strain amplitude by experimental and numerical investigations
    • Authors: Yong Wang; Yan-Li Wang
      Pages: 388 - 396
      Abstract: Publication date: January 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 92
      Author(s): Yong Wang, Yan-Li Wang
      In order to investigate the liquefaction behavior and meso-mechanism of gravelly soil under cyclic loading with constant strain amplitude, the undrained dynamic triaxial test, CT scan test and numerical simulations by discrete element method (DEM) are performed. Effects of gravel content and the evolution of liquefaction nmeso-mechanism are analyzed respectively. Test Results show that the liquefaction resistance of gravelly soil increases considerably with the increasing gravel content due to growing in number of gravel-to-gravel contact. DEM simulations reflect the macro mechanical property of saturated gravelly soil in the cyclic triaxial test, and show anisotropy is the most important mechanical properties of gravelly soil liquefaction under cyclic loading with constant strain amplitude. In process of the liquefaction, the backbone force-chain is gradually destroyed, and magnitude of normal contact force decreases to zero until initial liquefaction. Both of the fabric and force-chain evolution demonstrate a consistent deflection of the principal stress axis.

      PubDate: 2016-11-06T22:13:55Z
      DOI: 10.1016/j.soildyn.2016.10.029
      Issue No: Vol. 92 (2016)
       
  • Reliability assessment on earthquake early warning: A case study from
           Taiwan
    • Authors: Yun Xu; J.P. Wang; Yih-Min Wu; Hao Kuo-Chen
      Pages: 397 - 407
      Abstract: Publication date: January 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 92
      Author(s): Yun Xu, J.P. Wang, Yih-Min Wu, Hao Kuo-Chen
      Earthquake early warning (EEW) has been implemented in several regions around the world. However, because of natural randomness and uncertainty, false alarm and missed alarm can be expected in EEW. The key scope of this study is to evaluate the reliability of an on-site EEW in Taiwan, by testing the system's algorithm with 17,836 earthquake data from 1999 to 2013. The analysis shows that the on-site EEW system, empirically speaking, should have a false-alarm probability of 2.5%, and a missed-alarm probability of 14.1%. Considering missed alarm should be more critical to EEW, a new algorithm that could reduce the system's missed-alarm occurrences to 6% is also discussed in this paper.

      PubDate: 2016-11-06T22:13:55Z
      DOI: 10.1016/j.soildyn.2016.10.015
      Issue No: Vol. 92 (2016)
       
  • Anti-plane response caused by interactions between a dike and the
           surrounding soil
    • Authors: Wen-Shinn Shyu; Tsung-Jen Teng; Chuen-Shii Chou
      Pages: 408 - 418
      Abstract: Publication date: January 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 92
      Author(s): Wen-Shinn Shyu, Tsung-Jen Teng, Chuen-Shii Chou
      This paper proposes a novel strategy for the investigation of displacement amplitude ( u y ) near and along symmetric dikes comprising a trapezoidal structure with a circular-arc foundation when subjected to shear horizontal (SH) waves. Materials in the half-space dealt with two types of dike: (1) soft dikes, and (2) hard dikes. Modified transfinite interpolation (MTFI) was used to obtain the coordinates of nodes and determine the sequence of node numbering in the inner finite region, which included a dike and a semi-circular-arc annulus. MTFI was shown to overcome the difficulties involved in the meshing of irregularity. The proposed hybrid method, comprising finite element method and a Lamb series, was applied in conjunction with MTFI in order to study the effects of dike material, the incident angle of SH waves ( θ ), and a dimensionless frequency ( η ) on u y . We briefly describe a closed-form solution to the problem of rigid semi-cylindrical foundations proposed in a previous study and then conducted a comparison of theoretical solutions and numerical results obtained using the proposed hybrid method. In the case of soft dikes, the natural fixed-base frequency of the foundation was close to the quasi-resonance frequency (QRF), which resulted in a maximum value of u y ( u y max ) at the top of the trapezoidal structure for various η . However, in the case of hard dikes, the u y max at the top of trapezoidal structure and in the dike foundation appeared at various QRF due to the fact that the movement of a hard dike is close to a rigid body motion. Energy absorption in a soft dike was shown to be superior to that of a hard dike, based on the fact that the shape of the deformed soft dike was more complex than that of the hard dike, and a number of displacement peaks observed inside the soft dike may be indications of damage within the dike that must be taken into account. Interestingly, the proposed hybrid method with MTFI provides a better understanding of the soil-structure interaction, compared with results obtained in previous studies.
      Graphical abstract image

      PubDate: 2016-11-06T22:13:55Z
      DOI: 10.1016/j.soildyn.2016.10.014
      Issue No: Vol. 92 (2016)
       
  • Evaluation of the risk of sudden failure of a cohesive soil subjected to
           cyclic loading
    • Authors: Eliana Martínez; Hernán Patiño; Rubén Galindo
      Pages: 419 - 432
      Abstract: Publication date: January 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 92
      Author(s): Eliana Martínez, Hernán Patiño, Rubén Galindo
      This paper presents a proposed methodology to evaluate the risk of sudden failure experienced by a soft cohesive soil when acted upon by combined static and dynamic loading. The research is based on the results of a comprehensive experimental study in which 155 cyclic simple shear tests were performed on undisturbed specimens recovered at the port of Barcelona, Spain. The proposed experimental program is described in detail in addition to the systematic process of analysis to properly study and interpret the results obtained for samples subjected to cyclic loading. In general, the results indicate that the combination of monotonic and cyclic stresses governs pore water pressure generation, the pore water pressure generated during cyclic loading controls the risk of sudden failure, and by means of simple correlations among the stiffness modulus, the effective stresses, the cyclic strains and the number of cycles, it is possible to combine families of curves to allow for an evaluation of the risk of sudden failure.

      PubDate: 2016-11-06T22:13:55Z
      DOI: 10.1016/j.soildyn.2016.10.017
      Issue No: Vol. 92 (2016)
       
  • Characterization of the shear wave velocity in the metropolitan area of
           Málaga (S Spain) using the H/V technique
    • Authors: S. Rosa-Cintas; D. Clavero; J. Delgado; C. López-Casado; J.J. Galiana-Merino; J. Garrido
      Pages: 433 - 442
      Abstract: Publication date: January 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 92
      Author(s): S. Rosa-Cintas, D. Clavero, J. Delgado, C. López-Casado, J.J. Galiana-Merino, J. Garrido
      The H/V technique is used throughout this research to characterize the soil column at different locations of the metropolitan area of Málaga (Southern Spain). This region stands as a good example of a continuously growing zone, mostly developed on soft alluvial sediments, with moderate to low seismicity. The H/V analysis of the noise measurements reveals frequency peak values ranging from 3 to 4Hz on the NE of the study area, where the basin basement outcrops, to 0.3Hz in the Guadalhorce River alluvial plain. We correlate the presence of the main H/V peak with the appearance of the basin basement materials in the sedimentary column; whereas secondary peaks obtained in some measurement points may be related to Quaternary and Pliocene sedimentary fill. Shear wave velocity profiles, inverted from the experimental H/V curves, data available from previous boreholes and superficial geology information are all integrated to provide four characteristic 2D cross-sections of the basin. In the ground model described here we distinguish four layers: a shallow layer that is probably linked to the recent Quaternary sediments (Vs from 100 to 500m/s); an intermediate layer that is related to the presence of late Pliocene materials (Vs from 300 to 1000m/s); a deep layer associated with early Pliocene materials filling the trough formed by the basin basement (Vs from 700 to 1600m/s); and finally the basement formation that shows stable velocity at around 2000m/s.

      PubDate: 2016-11-06T22:13:55Z
      DOI: 10.1016/j.soildyn.2016.10.016
      Issue No: Vol. 92 (2016)
       
  • Metaheuristic based optimization of tuned mass dampers under earthquake
           excitation by considering soil-structure interaction
    • Authors: Gebrail Bekdaş; Sinan Melih Nigdeli
      Pages: 443 - 461
      Abstract: Publication date: January 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 92
      Author(s): Gebrail Bekdaş, Sinan Melih Nigdeli
      The aim of the study is to propose an optimization approach for optimum design of tuned mass dampers (TMDs) implemented to seismic structures considering soil-structure interaction (SSI). In the methodology, two metaheuristic algorithms such as harmony search algorithm and bat algorithm were employed. The present approaches evaluate time domain analyses of structure and consider the responses under several earthquake records. The optimum design variables defined as mass, period and damping ratio of TMD were searched for the optimization objective (minimization of the maximum displacement of structure) and the design constraint (limitation of the scaled stroke of TMD). The proposed methods were presented by using single degree of freedom structures for different soil characteristics, main structure periods and damping ratios. Also, a 40-story high-rise structure was investigated. For the 40-story structure, the optimally tuned TMDs are effective to reduce the critical displacement up to 25%. The proposed methodologies are both effective and feasible, but bat algorithm has advantages on the minimization of the optimization objective and finding a precise optimum value.

      PubDate: 2016-11-14T06:36:32Z
      DOI: 10.1016/j.soildyn.2016.10.019
      Issue No: Vol. 92 (2016)
       
  • Reduction of dynamic earth loads on flexible cantilever retaining walls by
           deformable geofoam panels
    • Authors: Ozgur L. Ertugrul; Aurelian C. Trandafir; M. Yener Ozkan
      Pages: 462 - 471
      Abstract: Publication date: January 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 92
      Author(s): Ozgur L. Ertugrul, Aurelian C. Trandafir, M. Yener Ozkan
      The potential application of geofoam in reducing the dynamic earth forces on flexible cantilever earth retaining walls was investigated through small-scale physical model tests. Tests were carried out using a state-of-the-art laminar container and a uniaxial shaking table. Deformable geofoam panels of low stiffness made from expanded polystyrene (EPS) and extruded polystyrene (XPS) geofoam were utilized as compressible inclusions in the present study. The dynamic stress-strain properties of these geomaterials are discussed based on results from laboratory cyclic triaxial tests. Lateral dynamic earth pressures and wall displacements at different elevations within the backfill were monitored during the application of various base excitations. The test results revealed that the presence of a deformable geofoam panel of low stiffness behind the flexible retaining wall will result in a reduction of the dynamic wall pressures and displacements. The geofoam efficiency in terms of load and displacement reduction decreases as the flexibility ratio of the model wall increases. On the other hand, load reduction efficiency of the geofoam increases as the amplitude and frequency ratio of the excitation increases. Load reduction efficiencies achieved in the tests were compared to those of the previous physical and numerical modeling studies available in the literature. Comparisons indicate that there is an agreement with the data presented in the previous modeling studies for low acceleration amplitudes and wall flexibility values, however, this agreement diminishes as wall flexibility begins to play role in reducing the earth pressures. Application point of the maximum dynamic thrust varies between 0.4 H to 0.6 H depending on the inclusion type, flexibility ratio of the wall and the characteristics of the harmonic motion applied to the base of the models.
      Graphical abstract image

      PubDate: 2016-11-14T06:36:32Z
      DOI: 10.1016/j.soildyn.2016.10.011
      Issue No: Vol. 92 (2016)
       
  • Estimation of floor response spectra using modified modal pushover
           analysis
    • Authors: Xiaolan Pan; Zhi Zheng; Zhenyu Wang
      Pages: 472 - 487
      Abstract: Publication date: January 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 92
      Author(s): Xiaolan Pan, Zhi Zheng, Zhenyu Wang
      A common approach to designing nonstructural components against seismic excitations involves the use of floor response spectra (FRS). FRS can be accurately computed only through a nonlinear time-history analysis of the structure subjected to a specific earthquake ground motion. However, for multi-storey structures, which are usually modeled as multi-degree-of-freedom (MDOF) systems, this analysis becomes computation-intensive and time-consuming and is not suitable for adopting in seismic design guidelines. An alternative method of estimating FRS on MDOF systems is presented here. The proposed method uses multiple ‘generalized’ or ‘equivalent’ single degree of freedom (ESDOF) systems to estimate FRS on a MDOF system within the context of a ‘modal pushover analysis (MPA)’. This is a modified version of the previous MPA procedure as it considers the contribution of the first mode to yielding of higher modes when obtaining multiple ESDOF systems. FRS values for each mode are obtained through nonlinear dynamic analysis of each ESDOF system and then the total FRS values are calculated for the considered modes according to the SRSS combination rule. The efficiency of the modified procedure is tested by comparing FRS based on this method with results from nonlinear dynamic analyses of MDOF systems, as well as estimates based on ESDOF systems built from the traditional MPA method, for several ground motion scenarios. Three steel moment frame structures, of 3-, 9-, and 20-storey configurations, are selected for this comparison. Bias statistics that show the effectiveness of the modified method are presented.

      PubDate: 2016-11-14T06:36:32Z
      DOI: 10.1016/j.soildyn.2016.10.024
      Issue No: Vol. 92 (2016)
       
  • Seismic response of pile-raft-clay system subjected to a long-duration
           earthquake: centrifuge test and finite element analysis
    • Authors: Lei Zhang; Siang Huat Goh; Huabei Liu
      Pages: 488 - 502
      Abstract: Publication date: January 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 92
      Author(s): Lei Zhang, Siang Huat Goh, Huabei Liu
      A series of seismic centrifuge model tests were performed to study the behavior of pile groups in soft kaolin clay. Several small-scale pile-raft models were fabricated, ranging from a 2×1 to a 4×3 pile group. Pile and raft were made of aluminum, rigidly connected each other at the pile head via a through bolt system. The excited long-duration ground motion of about 200s strong motion was employed to represent a far-field earthquake arising from Sunda Subduction Trench. Experimental investigation into the influence of group size on both raft acceleration and pile bending moment response was conducted. It was found that both acceleration and pile bending moment response were influenced by stiffness-to-mass ratio of the pile-raft system; while pile spacing had no evident influence on acceleration response but significantly influenced the pile bending moment response. Besides, pile bending moment was also influenced by the row location of pile in the 4×3 pile group. Furthermore, by employing a hyperbolic-hysteretic soil constitutive model to model the kaolin clay, a series of three-dimensional finite element analyses were carried out to compare with the seismic centrifuge tests. Reasonably well comparisons between centrifuge test and numerical computed results were obtained, which suggest that the 3D finite element modelling procedure with a hyperbolic-hysteretic soil constitutive model can be extended to complement seismic centrifuge tests.

      PubDate: 2016-11-14T06:36:32Z
      DOI: 10.1016/j.soildyn.2016.10.018
      Issue No: Vol. 92 (2016)
       
  • Seismic wave amplification by topographic features: A parametric study
    • Authors: Babak Poursartip; Arash Fathi; Loukas F. Kallivokas
      Pages: 503 - 527
      Abstract: Publication date: January 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 92
      Author(s): Babak Poursartip, Arash Fathi, Loukas F. Kallivokas
      Despite the ever increasing adoption of wave motion simulations for assessing seismic hazard, most assessment/simulations are still based on a flat surface earth model. The purpose of this paper is to quantify the effect of topographic irregularities on the ground motion and local site response by means of parametric investigations in the frequency-domain of typical two-dimensional features. To this end, we deploy best-practice tools for simulating seismic events in arbitrarily heterogeneous formations; these include: a forward wave simulator based on a hybrid formulation encompassing perfectly-matched-layers (PMLs); unstructured spectral elements for spatial discretization; and the Domain-Reduction-Method that permits placement of the seismic source within the computational domain, thus allowing consideration of realistic seismic scenarios. Of particular interest to this development is the study of the effects that various idealized topographic features have on the surface motion when compared against the response that is based on a flat-surface assumption. We report the results of parametric studies for various parameters, which show motion amplification that depends, as expected, on the relation between the topographic feature's characteristics and the dominant wavelength. More interestingly, we also report motion de-amplification patterns.

      PubDate: 2016-11-14T06:36:32Z
      DOI: 10.1016/j.soildyn.2016.10.031
      Issue No: Vol. 92 (2016)
       
  • Vertical vibration of a massless flexible strip footing bonded to a
           transversely isotropic multilayered half-plane
    • Authors: Zhi Yong Ai; Hai Tao Li; Yi Fan Zhang
      Pages: 528 - 536
      Abstract: Publication date: January 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 92
      Author(s): Zhi Yong Ai, Hai Tao Li, Yi Fan Zhang
      A rigorous analytical method is developed to analyze the vertical vibration of a massless flexible strip footing bonded to a transversely isotropic multilayered half-plane. The analytical layer-element solution for a transversely isotropic multilayered half-plane in the Fourier transform domain is first introduced for the later derivation. A pair of dual integral equations of contact stress and deflection is derived by virtue of the preceding solution and the mixed boundary conditions. By means of the classic plate theory and Jacobi orthogonal polynomials, the dual integral equations are further converted to a system of linear equations. Comparisons with existed solutions confirm the accuracy of the proposed method. More examples are given to illustrate the influence of relative rigidity ratio, transversely isotropy, double-layered characters and stratification on the vertical impedance and the contact stress.

      PubDate: 2016-11-14T06:36:32Z
      DOI: 10.1016/j.soildyn.2016.10.023
      Issue No: Vol. 92 (2016)
       
  • Evaluation of the seismic performance of a caisson and an L-type quay
           wall
    • Authors: Y. Yuksel; Z.T. Yuksel; E. Cevik; K. Orhan; M. Berilgen
      Pages: 537 - 550
      Abstract: Publication date: January 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 92
      Author(s): Y. Yuksel, Z.T. Yuksel, E. Cevik, K. Orhan, M. Berilgen
      The damage caused by earthquakes in the past twenty years has revealed a generally high vulnerability of port structures. This fact, together with consideration of the economic importance of port structures, indicates the need for better seismic design approaches for berth structures and cargo handling facilities. In the recent decades, there have been many incidences of failure of gravity quay walls. These failures have stimulated great progress in the development of performance-based design methods. In this paper, several of these design approaches were studied experimentally and analytically. A series of shaking tank 1 g tests was performed using 1/15 scaled a caisson and an L-type quay wall with two different gravel backfill materials on firm sea bed conditions without liquefaction under different sinusoidal seismic loads. 1 g shaking tank tests were executed to verify the applicability of the sliding block concept and to estimate the performances of these quay wall types The shaking tank tests provided insight into the wall displacements and the dynamic thrusts by analyzing force components at the contact surface between the saturated gravel backfill soil and the wall.

      PubDate: 2016-11-14T06:36:32Z
      DOI: 10.1016/j.soildyn.2016.10.013
      Issue No: Vol. 92 (2016)
       
  • “Site response analysis considering strain compatible site
           period”
    • Authors: Hoss Hayati; Robb E.S. Moss
      Pages: 551 - 560
      Abstract: Publication date: January 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 92
      Author(s): Hoss Hayati, Robb E.S. Moss
      In practice it is common to estimate site effects using a single proxy, or single variable such as 30m shear wave velocity (V S30 ) or site period. Many studies have investigated merits of proposed proxies with contradicting recommendations. Yet, most studies indicate the single proxy approach is less than ideal, resulting in large uncertainty. To provide a better understanding of components that drive site response, we performed a parameterized study on 19 shallow soil profiles with V S ranging from 150m/s to 400m/s. We propagated 74 input motions through each soil column using one-dimensional equivalent-linear method to produce 1406 site response analyses. The resulting amplification factors (the ratio of surface to base motion) were then analyzed statistically to identify trends. The mean amplification factor, averaged from 74 records, was used to isolate and quantify the effects of V S on site response. Based on analysis of record-to-record trends, we identified two separate mechanisms through which nonlinearity affects site response including “damping increase” and “site period shift”. The interaction of these two mechanisms makes amplification-shaking intensity models highly depth-dependent. The residual standard deviation of amplification factor based on depth-independent models was found to be up to three times larger than the corresponding standard deviation based on depth-specific models. We found strain compatible site period a promising site parameter that complements the predictive information obtained from V S . Finally, a simplified procedure providing a five-point estimate of site transfer function is outlined. The proposed procedure can fill the gap in current practice for an intermediate solution between the numerically rigorous solution and the single proxy approach. Implementation of this procedure is demonstrated in an example.

      PubDate: 2016-11-14T06:36:32Z
      DOI: 10.1016/j.soildyn.2016.10.010
      Issue No: Vol. 92 (2016)
       
  • Estimation of strong motion parameters in the coastal region of gujarat
           using geotechnical data
    • Authors: Kapil Mohan; B.K. Rastogi; Vasu Pancholi; B. Sairam
      Pages: 561 - 572
      Abstract: Publication date: January 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 92
      Author(s): Kapil Mohan, B.K. Rastogi, Vasu Pancholi, B. Sairam
      Seven boreholes are drilled in the coastal region of Gujarat; three in Kachchh (at Jangi, Mandvi and Mundra), one in Saurashtra (Jodiya) and three in mainland Gujarat(Dahej, Kamboi and Dholera) to depth of 27–80m for estimating the surface strong ground motion parameters. These parameters are required for seismic resistant design of structures in the areas. The adopted methodology comprises of three parts: (i) soil modeling and estimation of depth to Engineering Bed Layer (EBL) (a prominent subsurface soil layer with shear wave velocity of 450m/s to 760m/s with SPT N value of more than 80) (ii) Estimation of the ground motion at EBL (iii) estimation of ground motion at the surface by 1D ground response analysis using SHAKE program. The soil models are prepared from borehole data and shear wave velocity/ N-values. The ground motion at EBL is estimated using Stochastic Finite Fault source Modeling Technique by considering scenario earthquakes along two major faults of Kachchh (Kachchh Mainland Fault (Mw7.6) and Katrol Hill Fault (Mw7.5)), one of Saurashtra (North Kathiawar Fault (Mw 6.5)) and one of Mainland Gujarat (West Cambay Fault (Mw 6.0)). The surface ground motion is estimated by passing ground motion simulated at EBL through prepared soil models of each site using SHAKE program. The surface peak ground acceleration from 0.076g to 0.396g and peak spectral acceleration from 0.24g to 1.4g are estimated at seven coastal sites. Spectral accelerations are found higher than Bureau of Indian Standard (BIS) suggested values at Jangi (between 0.1 and 0.3s & 0.8–1.4s), Jodiya (0.1–0.3s), Mundra (0.3–0.6s) and Dholera (0.1–0.4s) sites, where the importance factor of 1.5 needs to be considered. The study suggests taking BIS values at Dahej, Kamboi and Mandvi coastal sites.

      PubDate: 2016-11-14T06:36:32Z
      DOI: 10.1016/j.soildyn.2016.10.021
      Issue No: Vol. 92 (2016)
       
  • Finite element modeling of soil-pile response subjected to
           liquefaction-induced lateral spreading in a large-scale shake table
           experiment
    • Authors: Gangjin Li; Ramin Motamed
      Pages: 573 - 584
      Abstract: Publication date: January 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 92
      Author(s): Gangjin Li, Ramin Motamed
      This paper presents two-dimensional (2D) nonlinear dynamic finite element (FE) modeling of a large-scale shake table test conducted at the E-Defense shake table facility in Japan. This study explores the efficiency of 2D effective stress analyses to predict the behavior of soil-pile systems subjected to liquefaction and lateral spreading using the library of existing constitutive models and the prescribed parameters. The coupled soil-water FE model was developed in OpenSees and the analysis results are compared with measured data from the shake table experiment with the main emphasis on the response of liquefied soil and the demand applied to the piles as well as the sheet-pile quay wall. By examining the numerical analysis results, it is demonstrated that the FE model was able to reproduce the shake table model behavior with reasonable accuracy. Lastly, a mitigation strategy was modeled to investigate its effectiveness to reduce the demand on the soil-pile system.

      PubDate: 2016-11-14T06:36:32Z
      DOI: 10.1016/j.soildyn.2016.11.001
      Issue No: Vol. 92 (2016)
       
  • In-plane soil-structure interaction in layered, fluid-saturated,
           poroelastic half-space II: Pore pressure and volumetric strain
    • Authors: Jianwen Liang; Jia Fu; Maria I. Todorovska; Mihailo D. Trifunac
      Pages: 585 - 595
      Abstract: Publication date: January 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 92
      Author(s): Jianwen Liang, Jia Fu, Maria I. Todorovska, Mihailo D. Trifunac
      Parts I and II of this paper present a study of linear in-plane soil-structure interaction in fluid-saturated, poroelastic, layered half-space using the Indirect Boundary Element Method (IBEM). The structure is a shear wall supported by a rigid embedded foundation. Part I presented the methodology and results for the foundation and structure responses. Part II (this paper) presents a parametric study in the frequency domain of the pore pressure, and of the volumetric strain in the solid frame and the pore fluid (water in this case) along the soil-foundation interface and the ground surface. The presented results are for the special case of a single soil layer over bedrock, semi-circular foundation and zero seepage force. The analysis of peaks in the pore pressure response versus dimensionless frequency suggests that they occur near the system frequencies and near the soil layer resonant frequencies, to a degree that depends on the incident wave. For example, for vertically incident SV wave, they occur mostly near the system frequencies, while, for incident P wave, they occur also near the soil layer resonant frequencies. The results of this linear model may be useful for better understanding of how the soil-structure interaction contributes to pore pressure buildup near foundations of structures, which may eventually lead to soil liquefaction and severe consequences in the stability of the structure.

      PubDate: 2016-11-14T06:36:32Z
      DOI: 10.1016/j.soildyn.2016.10.012
      Issue No: Vol. 92 (2016)
       
  • Comparative analysis on spatiotemporal pore pressure evolution under
           surface–wave perturbations
    • Authors: Yu Zhang; Ping Ping; Shuangxi Zhang; Pan Deng
      Pages: 596 - 603
      Abstract: Publication date: January 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 92
      Author(s): Yu Zhang, Ping Ping, Shuangxi Zhang, Pan Deng
      The near surface spatiotemporal pore pressure fluctuations in a porous half space induced by seismic surface–wave perturbations in different poroelastic regimes are analytically compared. The results for the pore pressure in the space–time domain are derived by inverse transforms of the fundamental solutions of dynamic poroelasticity in the frequency–wavenumber domain. Different poroelastic regimes depend on the different low frequency approximation for Biot's multi wave mode physical behaviors. In low seismic frequency band, whereas the fast wave mode inference can generate surface wave along the interface, fluid pressure is also significantly perturbated as in solid phase, but behaves as a slow P2 mode reflected by the R surface wave. It is also shown that the amount of induced pore pressure fluctuations are different by P2 diffusivity (dispersion–difusivity regime, DD and non–dispersion–diffusivity regime, NDD) and P2 wave (full–wave regime, FW). The strong solid and fluid coupling on the interface generates the transferred RP2 mode. Therefore, the decoupled viscoleastic approximation (VA) does not represent these near surface fluid characteristics. The results can be applied to predict near surface pore pressure responses under seismic perturbations, or as a benchmark for other numerical approaches for pressure solutions in a dynamic poroelastic half space, and also favor a potential interpretation for near surface soil liquefaction failure.

      PubDate: 2016-11-14T06:36:32Z
      DOI: 10.1016/j.soildyn.2016.10.032
      Issue No: Vol. 92 (2016)
       
  • Seismic performance of reinforced concrete frame buildings in Bhutan based
           on fuzzy probability analysis
    • Authors: K. Thinley; H. Hao
      Pages: 604 - 620
      Abstract: Publication date: January 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 92
      Author(s): K. Thinley, H. Hao
      Seismic performance of reinforced concrete (RC) frame buildings is mostly assessed based on the distinct interstorey drift limits defined by many existing guidelines. In reality, damage of a structure is a continuous process under the action of the load and also depends on a number of factors. Therefore damage can be more logically defined with a fuzzy performance level than a distinct interstorey drift limit. In this paper, probability and fuzzy set theory are used to estimate the realistic failure probabilities of the RC buildings in Bhutan by considering randomness in material and geometrical parameters and fuzziness in the damage criteria. Three typical RC frame buildings in Thimphu, Bhutan and the ground motions predicted at the generic soil sites in Thimphu are used for the structural response prediction. Rosenbluth Point Estimate Method is used for modelling the statistical variation of the input parameters and the computer program Perform 3D is used for carrying out the dynamic nonlinear analysis of the buildings. Monte Carlo Simulation is employed to validate the accuracy of the Rosenbluth Point Estimate Method and determine the statistical distribution of the response quantities. Soil structure interaction (SSI) is considered at the soft soil site using the uncoupled spring model. Based on the mean and standard deviation of the intersotrey drifts obtained from the analyses, the fuzzy failure probabilities of the buildings are estimated. It is found that under the 475 year return period ground motions, typical buildings experience a high probability of irreparable and severe damages, while the high probability of severe damage and complete collapse are predicted under the 2475 year return period ground motions. SSI is found to be detrimental to the 3 storey building, while no significant effect is observed to the 6 storey building.

      PubDate: 2016-11-14T06:36:32Z
      DOI: 10.1016/j.soildyn.2016.11.004
      Issue No: Vol. 92 (2016)
       
  • Nonlinear seismic response of a gravity dam under near-fault ground
           motions and equivalent pulses
    • Authors: Y. Yazdani; M. Alembagheri
      Pages: 621 - 632
      Abstract: Publication date: January 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 92
      Author(s): Y. Yazdani, M. Alembagheri
      In this paper, the nonlinear seismic response of gravity dams to forward-directivity and ordinary (non forward-directivity) near-fault earthquake ground motions is investigated. Considering Pine Flat dam as case study, it is numerically modeled along with its full reservoir using the finite element method. Two sources of nonlinearity are considered in the analysis: (1) the material nonlinearity of dam concrete, and (2) the geometric nonlinearity by inserting a joint at the base of the dam. Seventy-five forward-directivity and sixty ordinary near-fault ground motions are used to obtain statistically significant results. The equivalent representative pulses of the selected forward-directivity ground motions are extracted using a well-known methodology. The dam-reservoir model is analyzed under the equivalent pulses as well to identify the cases for which the equivalent pulses can capture the structural response to the actual forward-directivity ground motions. Finally, the effects of pulse period, amplitude and energy on the seismic response of the dam-reservoir system are studied.

      PubDate: 2016-11-14T06:36:32Z
      DOI: 10.1016/j.soildyn.2016.11.003
      Issue No: Vol. 92 (2016)
       
 
 
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