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EARTH SCIENCES (470 journals)

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Journal Cover Soil Dynamics and Earthquake Engineering
  [SJR: 1.516]   [H-I: 56]   [14 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0267-7261
   Published by Elsevier Homepage  [3051 journals]
  • Experimental assessment of cyclic behavior of sand-fouled ballast mixed
           with tire derived aggregates
    • Authors: M. Esmaeili; P. Aela; A. Hosseini
      Pages: 1 - 11
      Abstract: Publication date: July 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 98
      Author(s): M. Esmaeili, P. Aela, A. Hosseini
      This study deals with the application of tire derived aggregate (TDA) mixed with ballast material as an approach for enhancing the ballasted track performance in the presence of sand fouling. In order to assess the TDA influence on sand-fouled ballast, a series of ballast box tests was conducted on various mixtures of TDA, ballast material with AREMA 4A gradation and the Tabas desert windy sand with particle size range of 0.075–4.75mm. A total number of 36 cyclic uniaxial tests were performed by considering four TDA weight percentages of 0%, 5%, 10% and 15% as well as three weight percentages of 0%, 50% and 100% for windy sand as the contaminant. The gradation of TDAs was similar to that of ballast particles so as not to disturb the ballast layer drainage. On the basis of the laboratory outputs, the settlement, ballast breakage and damping ratio of samples were discussed. The experimental results indicate that increasing the sand percentage decreases the damping ratio, while leading to an increase in the settlement and ballast breakage of samples. Alternatively, these parameters escalated with the increase of TDA percentage. Overall, the 5%-TDA sample was determined as the most suitable mixture in terms of breakage and stiffness, whereas the more TDAs continuously increased the damping ratio of samples. Three regression equations were also derived to evaluate these parameters as functions of the number of loading cycles, TDA and sand percentages.

      PubDate: 2017-04-10T23:14:28Z
      DOI: 10.1016/j.soildyn.2017.03.033
      Issue No: Vol. 98 (2017)
       
  • Experimental and numerical study on the seismic behavior of anchoring
           frame beam supporting soil slope on rock mass
    • Authors: Yu-liang Lin; Ying-xin Li; Guo-lin Yang; Yun Li
      Pages: 12 - 23
      Abstract: Publication date: July 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 98
      Author(s): Yu-liang Lin, Ying-xin Li, Guo-lin Yang, Yun Li
      The anchoring frame beam is a widely used supporting structure in slope engineering. In this work, the dynamic behavior of anchoring frame beam under earthquake loading was studied by means of shaking table test and dynamic numerical simulation. The results of numerical simulation were compared with the test results in terms of the horizontal acceleration amplification, the vertical acceleration amplification, and the time history of displacement response. The behavior of axial stress of anchor was mainly studied by dynamic numerical simulation. The numerical results are generally consistent with those apparent in shaking table test. The results show that the natural frequency of the supported soil slope presents a decreasing trend during the shaking table test. The soil slope performs an amplification effect on input horizontal acceleration in time domain, and the energy within a frequency range that is around the natural frequency of soil slope is also amplified. Both the horizontal and the vertical acceleration amplifications present an increasing trend with the increase in input acceleration. The acceleration amplification differs greatly under different seismic motions. The frame beam presents a translation displacement together with a rotation around the vertex of frame beam. The residual deformation of frame beam increases obviously with the increase of input acceleration. A larger value of axial stress is observed at the anchor located at the bottom of frame beam. The axial stress of anchor decreases rapidly in anchorage segment, and it tends to zero within a short length under Wenchuan shaking event. The distribution curve of axial stress along the length of anchor presents two peak values after earthquake loading, which is much different from that induced by the self-weight.

      PubDate: 2017-04-10T23:14:28Z
      DOI: 10.1016/j.soildyn.2017.04.008
      Issue No: Vol. 98 (2017)
       
  • Effects of duration and acceleration level of earthquake ground motion on
           the behavior of unreinforced and reinforced breakwater foundation
    • Authors: Babloo Chaudhary; Hemanta Hazarika; Kengo Nishimura
      Pages: 24 - 37
      Abstract: Publication date: July 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 98
      Author(s): Babloo Chaudhary, Hemanta Hazarika, Kengo Nishimura
      This paper describes an effective reinforcement technique for foundation of breakwater in order to provide resiliency to the breakwater against earthquake and tsunami related compound geo-disaster. As reinforcing measures, the technique uses gabions and sheet piles in the foundation of the breakwater. A series of shaking table tests were performed to evaluate the effectiveness of the technique under different earthquake loadings, and comparisons were made between conventional and reinforced foundation. The results of these tests reveal the advantages of the reinforcing foundation technique in terms of reduction in settlement and horizontal displacement of the breakwater during the earthquake loadings. Duration and level of acceleration of earthquake loadings had significant impacts on the settlement and horizontal displacement of the breakwater. It was found that one of the reasons of settlement of the breakwater is lateral flow of foundation soils during earthquake, and the sheet piles could reduce the lateral flow. The excess pore water pressures could be reduced significantly during earthquake due to the reinforcing technique. Numerical analyses were also performed to confirm the effectiveness of the technique, and to determine behavior of the reinforcement-soil-breakwater system during the earthquakes.

      PubDate: 2017-04-10T23:14:28Z
      DOI: 10.1016/j.soildyn.2017.04.006
      Issue No: Vol. 98 (2017)
       
  • Assessment of alternative simulation techniques in nonlinear time history
           analyses of multi-story frame buildings: A case study
    • Authors: Shaghayegh Karimzadeh; Aysegul Askan; Ahmet Yakut; Gabriele Ameri
      Pages: 38 - 53
      Abstract: Publication date: July 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 98
      Author(s): Shaghayegh Karimzadeh, Aysegul Askan, Ahmet Yakut, Gabriele Ameri
      In regions with sparse ground motion data, simulations provide alternative acceleration time series for evaluation of the dynamic response of a structure. Different ground motion simulation methods provide varying levels of goodness of fit between observed and synthetic data. Before using the seismologically acceptable synthetic records for engineering purposes, it is critical to investigate the efficiency of synthetics in predicting observed seismic responses of structures. For this purpose, in this study we present nonlinear time history analyses of multi-story reinforced concrete frames under observed and synthetic records of a particular earthquake. Synthetic records of 6 April 2009 L′Aquila (Italy) earthquake (Mw=6.3) are simulated using both the Hybrid Integral-Composite method and the Stochastic Finite-Fault method. Results of analyses from observed and the alternative synthetic records of this event are compared in terms of maximum displacement, acceleration and plastic beam rotation of each story level. Our results indicate that the match between the Fourier Amplitude Spectrum of the observed and synthetic records around the frequencies that correspond to the fundamental period of the structure (mainly within 0.2–1.2% of the fundamental period) governs the misfit between the observed and synthetic nonlinear responses. It is also shown that even for cases where nonlinear behavior is more likely, period-dependent SDOF indicators of goodness of fit between a particular observed and corresponding synthetic records represents the difference in MDOF behavior of frame structures due to these records. Finally, simulation of realistic amplitudes over the entire broadband frequency range of interest is found to be critical while using the synthetics for earthquake engineering purposes.

      PubDate: 2017-04-17T23:19:36Z
      DOI: 10.1016/j.soildyn.2017.04.004
      Issue No: Vol. 98 (2017)
       
  • Seismic microzoning of Štip in Macedonia
    • Authors: V.W. Lee; M.D. Trifunac; B.Đ. Bulajić; M.I. Manić; D. Herak; M. Herak; G. Dimov; V. Gičev
      Pages: 54 - 66
      Abstract: Publication date: July 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 98
      Author(s): V.W. Lee, M.D. Trifunac, B.Đ. Bulajić, M.I. Manić, D. Herak, M. Herak, G. Dimov, V. Gičev
      Seismic microzonation maps for Štip (Macedonia) and its surroundings are presented based on the uniform-hazard-spectrum (UHS) methodology. Such mapping satisfies the guidelines for performance-based design (PBD), which requires specification of two sets of spectral amplitudes—one for which the structure will remain essentially linear, and the other for which it will undergo a nonlinear response. The UHS method also enables us to include contributions from excitation by large distant earthquakes as well as the simultaneous effects of site geology and site soils. Thus, the maps we present include, in a balanced way, the effects of near and distant large earthquakes, spatial distribution of seismic activity, the site geology, and the site soil properties.

      PubDate: 2017-04-17T23:19:36Z
      DOI: 10.1016/j.soildyn.2017.04.003
      Issue No: Vol. 98 (2017)
       
  • A novel method for identifying surface waves in periodic structures
    • Authors: Xingbo Pu; Zhifei Shi
      Pages: 67 - 71
      Abstract: Publication date: July 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 98
      Author(s): Xingbo Pu, Zhifei Shi
      In this study, the propagation of surface waves in both one- and two-dimensional periodic structures is investigated. By combining finite element method, an energy distribution parameter is defined and a new method for identifying surface wave modes is suggested. The effectiveness of this new method is validated by comparing with some related studies. Furthermore, this method is used to study a two-dimensional periodic pile-soil system based on a three-dimensional numerical model and the dispersion curves of surface waves are easily obtained. To show the efficiency of attenuation zone, the responses of a finite periodic pile-soil system to a surface wave input are simulated. Results demonstrate that the region of excitation frequency in which vibration reduction occurs is fully consistent with the theoretical attenuation zone for surface waves. The advantage of this method is that it makes the study of surface waves more convenient and accurate.

      PubDate: 2017-04-17T23:19:36Z
      DOI: 10.1016/j.soildyn.2017.04.011
      Issue No: Vol. 98 (2017)
       
  • On correlations between “dynamic” (small-strain) and “static”
           (large-strain) stiffness moduli – An experimental investigation on 19
           sands and gravels
    • Authors: T. Wichtmann; I. Kimmig; T. Triantafyllidis
      Pages: 72 - 83
      Abstract: Publication date: July 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 98
      Author(s): T. Wichtmann, I. Kimmig, T. Triantafyllidis
      Correlations between “dynamic” (small-strain) and “static” (large-strain) stiffness moduli for sand are examined. Such correlations are often used for a simplified estimation of the dynamic stiffness based on static test data. The small-strain shear modulus G dyn = G max and the small-strain constrained modulus M dyn = M max have been measured in resonant column (RC) tests with additional P-wave measurements. Oedometric compression tests were performed in order to determine the large-strain constrained modulus M stat = M oedo , while the large-strain Young's modulus E stat = E 50 was obtained from the initial stage of the stress-strain-curves measured in drained monotonic triaxial tests, evaluated as a secant stiffness between deviatoric stress q=0 and q = q max / 2 . Experimental data for 19 sands or gravels with specially mixed grain size distribution curves, having different non-plastic fines contents, mean grain sizes and uniformity coefficients, were analyzed. Based on the present data, it is demonstrated that a correlation between M max and M oedo proposed in the literature underestimates the dynamic stiffness of coarse and well-graded granular materials. Consequently, modified correlation diagrams for the relationship M max ↔ M oedo are proposed in the present paper. Furthermore, correlations between G max and M oedo or E 50, respectively, have been also investigated. They enable a direct estimation of dynamic shear modulus based on static test data. In contrast to the correlation diagram currently in use, the range of applicability of the new correlations proposed in this paper is clearly defined.

      PubDate: 2017-04-17T23:19:36Z
      DOI: 10.1016/j.soildyn.2017.03.032
      Issue No: Vol. 98 (2017)
       
  • Applicability of the N2, extended N2 and modal pushover analysis methods
           for the seismic evaluation of base-isolated building frames with lead
           rubber bearings (LRBs)
    • Authors: Hossein Nakhostin Faal; Mehdi Poursha
      Pages: 84 - 100
      Abstract: Publication date: July 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 98
      Author(s): Hossein Nakhostin Faal, Mehdi Poursha
      In the recent investigations, the pushover analysis has been mainly used for the seismic evaluation of fixed-base structures, whereas a limited number of research investigations have focused on the applicability of pushover analysis to base-isolated buildings. Therefore, this study attempts to extend the modal pushover analysis (MPA) and the extended N2 (EN2) method to medium-rise base-isolated building frames to account for the effect of higher modes in predicting the seismic demands of these structures. Since the displacement at the isolation level and subsequently the effective stiffness of the isolation system are not predetermined at first, an iterative process was used to fulfill the MPA method for base-isolated frames. The original N2 method, which was recently extended to base-isolated buildings, was also implemented with three different lateral load distributions, i.e. the inverted triangular, the first mode and the PSC load patterns. For this purpose, two steel moment-resisting building frames including low-rise (3-storey) and medium-rise (12-storey) ones were considered. The structures were isolated with lead rubber bearing (LRB) isolation systems. Three types of isolators with different stiffnesses including the hard (H), normal (N) and soft (S) isolators were selected. It was observed that N2 method with the PSC load distribution, in most cases, gives better estimates of the seismic demands for low-rise base-isolated frames. Also, the MPA and the EN2 methods can result in accurate estimates of the seismic demands for medium-rise base-isolated frames with the hard type isolators, but their accuracy deteriorates with the increase in the damping and decrease in the stiffness of isolators.

      PubDate: 2017-04-17T23:19:36Z
      DOI: 10.1016/j.soildyn.2017.03.036
      Issue No: Vol. 98 (2017)
       
  • Experimental study on seismic response of soil-nailed walls with permanent
           facing
    • Authors: Majid Yazdandoust
      Pages: 101 - 119
      Abstract: Publication date: July 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 98
      Author(s): Majid Yazdandoust
      A series of 1-g shaking table tests were performed on five reduced-scale soil-nailed wall models to investigate the influence of peak acceleration, loading duration, and nail length on seismic response of the soil-nailed walls in terms of the distribution of shear modulus (G) and damping ratio (D) in soil-nailed mass, the axial force distribution along the nails and the distribution of dynamic lateral earth pressure behind the surface. It was found that the seismic response of walls highly depends on the length of nails and input motion parameters. By introducing a new non-dimensional parameter (G global ) for soil-nailed walls, it was observed that the values of G, G/G 0 , and D are strongly dependent of confining pressure, L/H ratio, and shear strain levels, so that the variation trend of these parameters with γ is well expressed as an exponential equation with a high correlation coefficient. Additionally, a proper convergence was found between T max /H.γ s .S V .S H and L/H ratio at different levels of acceleration and duration, so that T max /H.γ s .S V .S H can be defined as a function of L/H ratio and seismic parameters for different rows of nail. Also, It was discovered that the values of predicated earth pressure by conventional methods in static and seismic conditions are too conservative and these methods predict the location of the resultant lateral earth pressure higher than the actual point.

      PubDate: 2017-04-17T23:19:36Z
      DOI: 10.1016/j.soildyn.2017.04.009
      Issue No: Vol. 98 (2017)
       
  • Scattering of plane qP- and qSV-waves by a canyon in a multi-layered
           transversely isotropic half-space
    • Authors: Zhenning Ba; Vincent W. Lee; Jianwen Liang; Yang Yan
      Pages: 120 - 140
      Abstract: Publication date: July 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 98
      Author(s): Zhenning Ba, Vincent W. Lee, Jianwen Liang, Yang Yan
      An indirect boundary element method (IBEM) is developed to study the scattering and diffraction of plane qP- and qSV-waves by a canyon in a multi-layered transversely isotropic (TI) half-space. First, the exact dynamic stiffness matrix for in-plane motion is constructed to determine the free fields of the multi-layered TI half-space for incident plane qP- and qSV-waves. Dynamic Green's functions for uniformly distributed loads acting on an inclined line are then derived and the scattered fields are expressed as the summation of dynamic responses of a set of fictitious distributed loads applied on the canyon surface. Finally, the boundary condition is introduced to determine the densities of the distributed loads and the total dynamic responses are recovered by adding the free fields to the scattered fields. The proposed IBEM has the merits of distributed loads being directly applied on the real boundary of the irregularity without the problem of singularity, and the discretization effort being restricted to the surface of the canyon. Comparisons with existing numerical solutions for the isotropic (special) case are conducted to confirm the validity of the proposed formulations. And parametric studies are performed in both the frequency and time domains to investigate the influence of material anisotropy, frequency of excitation, incident angle and layering on the surface motions. Numerical results show that the surface motions for the TI medium can be significantly different from those of the isotropic case and that the responses are highly dependent on the TI parameters, especially for the layered TI half-space.

      PubDate: 2017-04-17T23:19:36Z
      DOI: 10.1016/j.soildyn.2017.04.005
      Issue No: Vol. 98 (2017)
       
  • Damage demand assessment of mainshock-damaged concrete gravity dams
           subjected to aftershocks
    • Authors: Gaohui Wang; Yongxiang Wang; Wenbo Lu; Peng Yan; Wei Zhou; Ming Chen
      Pages: 141 - 154
      Abstract: Publication date: July 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 98
      Author(s): Gaohui Wang, Yongxiang Wang, Wenbo Lu, Peng Yan, Wei Zhou, Ming Chen
      In China, the current seismic codes specify a single earthquake event as the design seismic load for concrete gravity dams. However, a large mainshock usually triggers numerous aftershocks in a short period. This paper assesses the effects of aftershocks on concrete gravity dam–reservoir–foundation systems and provides a quantitative description of the damage demands prior to and following the aftershocks. For this purpose, a set of 20 as-recorded mainshock–aftershock seismic sequences is considered in this study. The correlation between the ground motion characteristics of the as-recorded mainshocks and those of the aftershocks is examined. In order to identify the influence of the ground motion characteristics of aftershocks on the damage demands of the mainshock-damaged dams, the nonlinear behavior of the concrete gravity dams that are subjected to single seismic events and typical as-recorded seismic sequences is compared in terms of the structural damage, displacement response, and damage dissipated energy. A series of nonlinear dynamic analyses is performed to quantify the influence of aftershocks, which are selected by using different methods, on the damage demands of concrete gravity dam–reservoir–foundation systems in terms of the local and global damage indices. The results show that the aftershocks lead to an increase in the damage demands of the dam at the end of the seismic sequence when the concrete gravity dam is already damaged during the first individual seismic event and has not been repaired. In addition, the results also reveal that the repeated seismic sequences tend to underestimate the level of damage demands.

      PubDate: 2017-04-17T23:19:36Z
      DOI: 10.1016/j.soildyn.2017.03.034
      Issue No: Vol. 98 (2017)
       
  • Double wall barriers for the reduction of ground vibration transmission
    • Authors: C. Van hoorickx; M. Schevenels; G. Lombaert
      Pages: 1 - 13
      Abstract: Publication date: June 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 97
      Author(s): C. Van hoorickx, M. Schevenels, G. Lombaert
      Stiff wall barriers can be effective in reducing the transmission of environmental ground vibration. Up to now, single wall barriers have mostly been studied. In building acoustics, however, double walls are used in order to realize a high level of sound insulation. In this paper, the potential of using double walls in reducing ground vibration transmission is investigated by means of numerical simulations. Two cases are studied: jet-grout walls and concrete walls in a homogeneous soil with elastic properties representative of a sandy soil. For both cases, the three-dimensional free field response due to a point load is computed using a 2.5D finite element methodology. Subsequently, the free field response is computed for a simplified train load. Double jet-grout wall barriers are found to be slightly more effective than single wall barriers, in particular when the thickness of the walls and the intermediate soil matches a quarter Rayleigh wavelength. The largest increase in vibration reduction is found for the area closest to the vibration source, where the vibration levels have the highest values. The performance of concrete wall barriers, however, is mainly determined by the stiffness of the walls, and almost no difference in performance is found for single and double walls.

      PubDate: 2017-03-09T06:56:09Z
      DOI: 10.1016/j.soildyn.2017.02.006
      Issue No: Vol. 97 (2017)
       
  • Response of the Christchurch water distribution system to the 22 February
           2011 earthquake
    • Authors: D. Bouziou; T.D. O’Rourke
      Pages: 14 - 24
      Abstract: Publication date: June 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 97
      Author(s): D. Bouziou, T.D. O’Rourke
      The effects of transient and permanent ground deformations during the 22 February 2011 earthquake on the Christchurch water distribution system are investigated through geospatial analysis with the most detailed and accurate databases currently available. Using the most recent repair records, ground motion records, high resolution Light Detection and Ranging (LiDAR) data collected before and after the earthquake, and improved screening criteria, repair rates, expressed as repairs/km, for different types of pipeline are correlated with 1) peak ground velocity outside liquefaction areas, and 2) differential ground surface lateral and vertical movements in liquefaction areas. The substantial influence of LiDAR resolution on the relationship between pipeline damage and lateral ground strain indicates sensitivity of repair regressions to the degree of data resolution. Repair regressions of different pipelines show that polyvinyl chloride pipelines are markedly more resilient to earthquake effects than other types of segmental pipelines in the Christchurch system. The analytical process is described in detail for assistance in future investigations with data sets of similar size and complexity.

      PubDate: 2017-03-09T06:56:09Z
      DOI: 10.1016/j.soildyn.2017.01.035
      Issue No: Vol. 97 (2017)
       
  • Effect of initial relative density on the post-liquefaction behaviour of
           sand
    • Authors: Mehdi Rouholamin; Subhamoy Bhattacharya; Rolando P. Orense
      Pages: 25 - 36
      Abstract: Publication date: June 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 97
      Author(s): Mehdi Rouholamin, Subhamoy Bhattacharya, Rolando P. Orense
      Understanding the behaviour of soils under cyclic/dynamic loading has been one of the challenging topics in geotechnical engineering. The response of liquefiable soils has been well studied however, the post liquefaction behaviour of sands needs better understanding. In this paper, the post liquefaction behaviour of sands is investigated through several series of multi-stage soil element tests using a cyclic triaxial apparatus. Four types of sand were used where the sands were first liquefied and then monotonically sheared to obtain stress-strain curves. Results of the tests indicate that the stress-strain behaviour of sand in post liquefaction phase can be modelled as a bi-linear curve using three parameters: the initial shear modulus ( G 1 ), critical state shear modulus ( G 2 ), and post-dilation shear strain ( γ p o s t − d i l a t i o n ) which is the shear strain at the onset of dilation. It was found that the three parameters are dependent on the initial relative density of sands. Furthermore, it was observed that with the increase in the relative density both G 1 and G 2 increase and γ p o s t − d i l a t i o n decreases. The practical application of the results is to generate p-y curves for liquefied soil.

      PubDate: 2017-03-09T06:56:09Z
      DOI: 10.1016/j.soildyn.2017.02.007
      Issue No: Vol. 97 (2017)
       
  • Soil liquefaction in Kathmandu valley due to 25 April 2015 Gorkha, Nepal
           earthquake
    • Authors: Dipendra Gautam; Filippo Santucci de Magistris; Giovanni Fabbrocino
      Pages: 37 - 47
      Abstract: Publication date: June 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 97
      Author(s): Dipendra Gautam, Filippo Santucci de Magistris, Giovanni Fabbrocino
      The April 25, 2015 Gorkha earthquake (MW 7.8) affected central Nepal and neighboring areas. Kathmandu valley witnessed severe damage in terms of structural collapse and casualties. Apart from this, soil liquefaction in the form of sand blows and lateral spreading were observed in 12 locations. Soil liquefaction in Kathmandu valley during 1934 (MW 8.1) earthquake was believed to be one of the major cause of damage in structures and lifelines but detail records are not available. To fulfill the gap of documentation in case of strong earthquake events like the Gorkha earthquake, field reconnaissance and collection of samples from each sand blow location have been carried out. In addition to this, numerical analyses based on geotechnical investigation records for seven locations that manifested sand blows have been performed. Common approach of liquefaction susceptibility analysis based on standard penetration resistance is found to be consistent with the surface manifestations. Our comparison between existing susceptibility maps and results of numerical analyses as well as field evidence concludes that the existing susceptibility maps are unrepresentative.

      PubDate: 2017-03-09T06:56:09Z
      DOI: 10.1016/j.soildyn.2017.03.001
      Issue No: Vol. 97 (2017)
       
  • Effects of frequency contents of aftershock ground motions on reinforced
           concrete (RC) bridge columns
    • Authors: Moochul Shin; Byungmin Kim
      Pages: 48 - 59
      Abstract: Publication date: June 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 97
      Author(s): Moochul Shin, Byungmin Kim
      This study focuses on exploring effects of frequency contents of aftershock ground motions on seismic responses of reinforced concrete (RC) bridge columns. It has been well recognized that RC columns damaged by a sizeable main shock event become more vulnerable to following aftershocks. Therefore, it is essential to use proper main shock-aftershock sequential ground motions in seismic analyses to ensure the safety and integrity of infrastructure. Using frequency –invariant scaling factors, conventional methods were developed in the past. These methods combine sequential ground motions when performing a time history nonlinear analysis. However, these conventional methods neglect frequency contents of aftershock ground motions, which are usually different from those of main shock ground motions. This research demonstrates the importance of properly representing aftershock ground motions in estimating seismic responses of RC columns, and presents the differences in frequency contents between aftershock ground motions and the corresponding main shock ground motions. Time history seismic analyses using a finite element analysis program OpenSees are carried out. First, main shock motions recorded during the 1994 Northridge, California, the United States of America, the 1997 Umbria-Mache, Italy and the 1999 Chi-Chi, Taiwan earthquakes are used in this study. Then, the corresponding aftershock motions are selected or obtained: (1) from recordings during the seismic events, (2) by scaling main shock (which represents a traditional method), or (3) by spectrally matching main shock motions to the aftershock motions. The peak displacements and residual displacements of the RC columns using the spectrally matched motions are closer to those results using real aftershock motion records, as opposed to using the scaled motions. This demonstrates that the frequency contents of aftershock ground motions have significant impacts on the seismic responses of RC columns.

      PubDate: 2017-03-09T06:56:09Z
      DOI: 10.1016/j.soildyn.2017.02.012
      Issue No: Vol. 97 (2017)
       
  • Dynamic variability response functions for stochastic wave propagation in
           soils
    • Authors: Theofilos-Ioannis Manitaras; Vissarion Papadopoulos; Manolis Papadrakakis
      Pages: 60 - 73
      Abstract: Publication date: June 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 97
      Author(s): Theofilos-Ioannis Manitaras, Vissarion Papadopoulos, Manolis Papadrakakis
      In this paper, shear wave propagation in soils is examined in a stochastic context considering spatial variability of the shear modulus soil parameter. To this purpose, the recently established concept of dynamic mean and variability response functions (DMRF, DVRF) is reformulated in the framework of stochastic finite element analyses of shear wave propagation problems in order to efficiently calculate the response time history statistics of the soil surface. Similarly to the approximation formulas of classical VRFs, a fast Monte Carlo simulation procedure is implemented to numerically evaluate the above functions in the time domain. The main advantage of the proposed methodology lies on the independence of the DMRF and DVRF on the marginal probability density function and correlation structure of the stochastic system parameter, which in our case is assumed to be the inverse of the soil shear modulus 1 / G . By integrating the product of the spectral density of 1 / G with the DMRF and DVRF, the mean and variance of the ground response are obtained at each time step of the dynamic analysis. The method also allows for the estimation of time dependent but spectral and probability distribution free upper bounds of the response mean and variance. To illustrate the efficiency and applicability of the proposed approach, stochastic finite element analyses of wave propagation of a Ricker synthetic wavelet as well as a recorded earthquake motion in 1D and 2D soil domains are performed and a sensitivity analysis is carried out with respect to various correlation structures of the underlying random fields representing 1 / G . The accuracy of the proposed methodology is validated with comparison to direct Monte Carlo simulation. Useful conclusions regarding the sensitivity of the system response to the spectral characteristics of the underlying random fields representing 1 / G are drawn.

      PubDate: 2017-03-09T06:56:09Z
      DOI: 10.1016/j.soildyn.2017.02.004
      Issue No: Vol. 97 (2017)
       
  • Equivalent damping of bilinear hysteretic SDOF system considering the
           influence of initial elastic damping
    • Authors: Tao Liu; Bruno Briseghella; Qilin Zhang; Tobia Zordan
      Pages: 74 - 85
      Abstract: Publication date: June 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 97
      Author(s): Tao Liu, Bruno Briseghella, Qilin Zhang, Tobia Zordan
      The premise of equivalent linearization method is that the peak response of an inelastic system can be estimated as the peak response of a linear elastic system having reduced stiffness and increased damping. Different approaches have been used to determine the properties of the equivalent linear system, in particular the equivalent damping ratio. In general, equivalent damping is specified as the sum of elastic and hysteretic component, where the former is assumed to be constant, and the latter depends on the ductility and hysteresis model. It is found that, however, many studies only focus on the definition of hysteretic damping and omit the influence of elastic damping on the prediction accuracy of equivalent linearization method. Motivated by this limitation, comprehensive parametric analysis is performed in this paper based on bilinear hysteretic SDOF systems to identify the influence of elastic damping. Results show that elastic damping has significant influence on the estimation accuracy of equivalent linearization method. To improve the estimation accuracy of equivalent linearization method, improved method of equivalent damping is proposed by considering the influence of elastic damping. It is found that the proposed method is able to provide accurate and conservative values of equivalent damping for practical design of base isolation systems.

      PubDate: 2017-03-09T06:56:09Z
      DOI: 10.1016/j.soildyn.2017.01.017
      Issue No: Vol. 97 (2017)
       
  • Comparative study of 2D and 2.5D responses of long underground tunnels to
           moving train loads
    • Authors: Y.B. Yang; Xujie Liang; Hsiao-Hui Hung; Yuntian Wu
      Pages: 86 - 100
      Abstract: Publication date: June 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 97
      Author(s): Y.B. Yang, Xujie Liang, Hsiao-Hui Hung, Yuntian Wu
      A comparative study is conducted for the responses of soil-tunnel systems to moving train loads using the 2D and 2.5D finite/infinite element approaches, considering the effects of train speed, rail roughness and floating slab. Focus is placed on the wheel-rail interaction forces in the presence of rail roughness. The following are the major findings of this paper: (1) For all the cases studied, the 2D soil response is always higher than the 2.5D response. (2) The 2D result (with plane strain condition) is the limit of the 2.5D analysis with infinite train speed for smooth rails. (3) The 2D frequency response function (FRF) is contributed by frequencies of the whole range, being less sensitive to variation in roughness frequencies, while the 2.5D FRF is affected seriously by the frequencies of rail roughness. (4) With the floating slab tracks, the velocity and acceleration predicted of the soil are largely reduced for frequencies above the threshold using both approaches. But for frequencies below the threshold, the 2D approach shows higher amplified response. In short, the 2D approach saves tremendous computation time, as the system matrices is relatively smaller. But the 2.5D approach is more realistic, since it can account for various factors of the half space, including rail roughness and wave transmission along the tunnel axis.

      PubDate: 2017-03-16T00:22:39Z
      DOI: 10.1016/j.soildyn.2017.02.005
      Issue No: Vol. 97 (2017)
       
  • Inelastic design spectra based on the actual dissipative capacity of the
           hysteretic response
    • Authors: Enzo Martinelli; Roberto Falcone; Ciro Faella
      Pages: 101 - 116
      Abstract: Publication date: June 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 97
      Author(s): Enzo Martinelli, Roberto Falcone, Ciro Faella
      This work is intended at generalising the μd-T-Rμ relationships, currently available in the literature for defining inelastic design spectra, with the aim to take into account the actual dissipative capacity of structural systems. In fact, the inelastic spectra currently adopted in Nonlinear Static Analyses are generally based on an ideal elastic-perfectly plastic behaviour. Therefore, a more general hysteretic law is considered for parameterising the dissipative capacity of the structural systems under consideration. Non Linear Time History analyses are carried out for evaluating their dynamic response. A calibration of the aforementioned μd-T-Rμ relationships is proposed for enhancing the accuracy of inelastic seismic design spectra and, hence, the resulting relationships widely adopted in seismic analysis procedures, such as the N2 Method.

      PubDate: 2017-03-21T00:40:27Z
      DOI: 10.1016/j.soildyn.2017.03.006
      Issue No: Vol. 97 (2017)
       
  • A Multi-step approach to generate response-spectrum-compatible artificial
           earthquake accelerograms
    • Authors: Khaldoon A. Bani-Hani; Abdallah I. Malkawi
      Pages: 117 - 132
      Abstract: Publication date: June 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 97
      Author(s): Khaldoon A. Bani-Hani, Abdallah I. Malkawi
      Time history records are essential for nonlinear dynamic analysis to determine the response of structures. Considering lack of enough earthquake records, generation of artificial earthquake records and spectrum-matched records are the best method in this regard. This study is motivated by real life applications of designing new structures or evaluating the performance of current ones in Afghanistan where two structures are to be designed and built to withstand earthquakes. In this paper, design response spectrum and time history records are generated for two sites located within the city of Kabul, Afghanistan. The Probabilistic Seismic Hazard Assessment (PSHA) results are employed initially to produce the required parameters and data. Then, the generalized nonstationary Kanai-Tajimi model is applied to simulate the ground acceleration time history using the identified characteristics of the site from preliminary ARMA (Auto Regressive Moving Average) analysis and the site-specific analysis. The response spectrum is developed and iteratively compared to the ARMA model and the site-specific spectrum until a satisfactory match is achieved. Finally, the time domain description of the spectrum-compatible artificial earthquake record is developed exploiting inverse FFT of the design response spectrum. The total errors in spectral matching generated accelerograms are compared to results from a commercially available software. Results demonstrated the effectiveness and robustness of the adapted approach.

      PubDate: 2017-03-21T00:40:27Z
      DOI: 10.1016/j.soildyn.2017.03.012
      Issue No: Vol. 97 (2017)
       
  • Effect of silt on post-cyclic shear strength of sand
    • Authors: Reza Noorzad; Milad Shakeri
      Pages: 133 - 142
      Abstract: Publication date: June 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 97
      Author(s): Reza Noorzad, Milad Shakeri
      Adding non-plastic fines to sand can greatly change its behavior. Size difference between sand and silt particles is the main reason which causes this change. While post-cyclic and post-liquefaction behavior of clay and clean sand has been widely studied, silty sand is wrongly considered to behave like clean sand and researches usually do not focus on it. In silty sand, through low cohesion, applying cyclic load can displace particles and result in heterogeneity within the mixture. Even if liquefaction does not occur, rearrangement of soil particles can affect monotonic ultimate strength. This study, with a series of post-cyclic monotonic triaxial tests, has shown that in sand with a considerable amount of silt, cyclic loading can change the ultimate state strength. In sand with 15% silt it decreases and in sand with 30% silt it increase the ultimate state strength. Changes are negligible in clean sand or sand with 5% silt.

      PubDate: 2017-03-21T00:40:27Z
      DOI: 10.1016/j.soildyn.2017.03.013
      Issue No: Vol. 97 (2017)
       
  • Directional effects of tectonic fractures on ground motion site
           amplification from earthquake and ambient noise data: A case study in
           South Iceland
    • Authors: Francesco Panzera; Benedikt Halldorsson; Kristín Vogfjörð
      Pages: 143 - 154
      Abstract: Publication date: June 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 97
      Author(s): Francesco Panzera, Benedikt Halldorsson, Kristín Vogfjörð
      The geology of SW-Iceland is characterized by alternating basaltic lava units, hyaloclastite formations, postglacial sedimentary filled valleys and alluvial plains, as well as highly fractured bedrock within the Reykjanes Peninsula volcanic rift zone and the South-Iceland transform fault system. Historic earthquakes within this region reach magnitudes 6.5–7. Using earthquake and ambient noise recordings from 15 seismic stations within the rift and transform zones we compared wavefield polarization and seismic site response in order to assess characteristics of local amplification of ground motion. Ambient noise and earthquake ground motion spectral ratios are comparable in frequency and can qualitatively be subdivided into three groups: one with a spectral ratio characterized by a single predominant frequency of horizontal amplification, one with a bi- or multimodal and one characterized by a relatively constant amplitude across the frequency range. Seismic wavefield polarization within the transform zone has a prevailing direction of amplification towards 110°−150°N in the frequency range 1.0–3.0Hz, having a quasi-perpendicular relationship with mapped faults and fractures. Shear wave splitting results show that the wavefield polarization and fast S wave directions tend to be orthogonal, i.e. highly dependent on the anisotropy of the medium.

      PubDate: 2017-03-27T13:17:23Z
      DOI: 10.1016/j.soildyn.2017.03.024
      Issue No: Vol. 97 (2017)
       
  • Numerical modeling of dip-slip faulting through granular soils using DEM
    • Authors: Mohammad Hazeghian; Abbas Soroush
      Pages: 155 - 171
      Abstract: Publication date: June 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 97
      Author(s): Mohammad Hazeghian, Abbas Soroush
      A GPU-based DEM modeling methodology with rolling resistance is employed to study comprehensively dip-slip faulting through granular soils from both engineering and fundamental viewpoints. From engineering viewpoints, the results of engineering significances, including the ruptures path, the fault outcropping location, the ground surface distortion zone, the near surface stress path within the rupture and the fault outcropping strain are studied. From fundamental viewpoints, the orientation of the ruptures (shear bands) is discussed using the Roscoe theory. The analyses show that the fault ruptures deviate from the fault projection surfaces as propagating up toward the ground surface; the deviation depends on the faulting type, faulting angle and soil density. The reverse ruptures may deviate from the fault projection surfaces toward the hanging wall or foot wall, depending on the fault dip angle; however, both primary and secondary normal ruptures refract at the soil-bedrock interface, deviating toward the hanging wall. In addition, the analyses show that by increasing the fault dip angle, the slopes of the near surface stress paths within the reverse ruptures increase from about the slope of the biaxial compression stress path to about that of the p-constant stress path (compressional regime); conversely, these slopes within the normal ruptures decrease from about the slope of the biaxial extension stress path to about that of the p-constant stress path (extensional regime). Moreover, the analyses show that the fault outcropping strains of reverse faulting are comparatively higher than those of normal faulting. In addition, the fault outcropping strains are proportional to the soil ductility. From fundamental viewpoints, the analyses show that all of the reverse and normal fault ruptures through the denser and looser sands do propagate in parallel with zero-extension lines of the localized areas located along the ruptures paths, provided that the variations of the maximum principal strain directions and dilatancy rates along the ruptures are taken into account; this is in accord with the Roscoe theory.

      PubDate: 2017-03-27T13:17:23Z
      DOI: 10.1016/j.soildyn.2017.03.021
      Issue No: Vol. 97 (2017)
       
  • Automatic event detection and picking of P, S seismic phases for
           
    • Authors: Zijun Wang; Boming Zhao
      Pages: 172 - 181
      Abstract: Publication date: June 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 97
      Author(s): Zijun Wang, Boming Zhao
      We proposed a set of high-precision combination algorithms to detect and pick seismic phases for the earthquake early warning (EEW). First by the polarisation analysis of the three-component seismograms, we developed two filters to separate P and S waves for each record through a sliding time window. Then based on the short term average/long term average characteristic function on the polarised traces, an amplification coefficient, in terms of δ, was introduced to be multiplied by the original ratio to sensitively reflect the changes of signals’ amplitude and frequency, where a better detection of the phase arrival was achieved. Next according to the preliminary detections, we used the Akaike information criteria function combined with the higher order statistics to refine the signal and lock on the arrival time with a higher degree of accuracy. We tested our techniques to the main-shock and aftershocks of the M s 8.0 Wenchuan earthquake, where hundreds of three-component acceleration records over magnitudes of M s 5.0 were treated. In comparison to the analyst picks, the results of the proposed detection algorithms were shown to perform well and can be applied for the early warning of impending earthquakes occurred with diverse focal mechanisms, complicated propagation process and site effects.

      PubDate: 2017-03-27T13:17:23Z
      DOI: 10.1016/j.soildyn.2017.03.017
      Issue No: Vol. 97 (2017)
       
  • A trivial way to construct a tripartite response spectrum grid
    • Authors: Eduardo Kausel
      Pages: 182 - 183
      Abstract: Publication date: June 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 97
      Author(s): Eduardo Kausel
      We demonstrate in this note a disarmingly simple and elementary way to construct a tri-logarithmic response spectrum grid, albeit restricted to the metric system. The reason is that we rely herein on the very close approximations for the acceleration of gravity g ≈ π 2 as well as π 2 ≈ 10 , whereas scales in the US Customary system of units do not benefit from these near coincidences. It is believed that the method proposed may be useful not only in an engineering office, but even more so in the context of a course on Structural Dynamics and Earthquake Engineering.

      PubDate: 2017-03-27T13:17:23Z
      DOI: 10.1016/j.soildyn.2017.03.022
      Issue No: Vol. 97 (2017)
       
  • Centrifuge modeling of seismic foundation-soil-foundation interaction on
           liquefiable sand
    • Authors: Y. Jafarian; B. Mehrzad; C.J. Lee; A.H. Haddad
      Pages: 184 - 204
      Abstract: Publication date: June 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 97
      Author(s): Y. Jafarian, B. Mehrzad, C.J. Lee, A.H. Haddad
      Liquefaction-induced settlement and bearing capacity failure have been reported as leading causes of damages in shallow foundations during earthquakes. Previous studies of this problem have mainly focused on the performance of isolated shallow foundations. In urban areas, however, foundations are generally located in close proximity. In this study, three series of centrifuge tests were conducted to investigate the effect of foundation-soil-foundation interaction (FSFI) on the seismic and post-seismic settlement of shallow foundations on saturated sand. Two rigid foundations with different surcharge loads (as heavy and light foundations) were placed with different spacing. Multiple shaking events were applied to achieve different extents of soil liquefaction. The results indicate that significant part of foundation settlement occurred before soil reconsolidation. Furthermore, the time period after shaking, wherein excess pore water pressure sustains, plays an important role in the total settlement of foundations. The acceleration responses experienced by the foundations were significantly larger than those observed in the free-field. The heavy foundation fluctuated more strongly than the light one. Moreover, adjacency considerably affected the seismic response of foundations whereas stronger acceleration response on the ground level was observed for the closer cases. The Clear asymmetric settlement was observed for the adjacent foundations. It is demonstrated that settlement of foundations not only is dependent on foundations' proximity but also is a function of shaking intensity. Influence of foundations' spacing on the generation-dissipation mechanism of excess pore water pressure (EPWP) and liquefaction extent was described by the time-dependent contours plotted by interpolation of the recorded data.

      PubDate: 2017-03-27T13:17:23Z
      DOI: 10.1016/j.soildyn.2017.03.019
      Issue No: Vol. 97 (2017)
       
  • Effects of seismic sequences on structures with hysteretic or damped
           dissipative behaviour
    • Authors: Giovanni Rinaldin; Claudio Amadio; Massimo Fragiacomo
      Pages: 205 - 215
      Abstract: Publication date: June 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 97
      Author(s): Giovanni Rinaldin, Claudio Amadio, Massimo Fragiacomo
      Repeated seismic events strongly affect the building capacity in earthquake-prone regions, as its resilience, intended as the capacity of a system to quickly revert to a fully operational state after a damage due to a significant event, depends on the ability to withstand cumulated damage. This paper investigates the effects of repeated seismic sequences on structures characterized by different hysteretic behaviour. To this aim, non-linear single-degree-of-freedom (SDOF) systems were subjected to ten recorded seismic sequences taken from literature. The elasto-plastic and pivot hysteresis rules were analysed first, considering both hardening and softening behaviour. From each analysis, the inelastic spectrum of the seismic sequence was computed for different ductility levels, and the ductility demand was calculated and compared with the values for an only seismic event. It was shown that the effect of seismic sequences is quite significant, and a reduction of the behaviour factor from 15% for bilinear with hardening and pivot hysteretic rules to 35% for elasto-plastic systems with high ductility should be adopted in design to increase the seismic resilience. The use of linear and non-linear viscous dampers was also analysed in SDOF systems subjected to seismic sequences, demonstrating the effectiveness of this mitigation measure. Nonlinear viscous dampers with an initial friction force were found to dramatically reduce the acceleration and displacement demand, although it cannot avoid residual displacements at the end of the seismic events, and can be recommended for structures with short vibration periods. Nonlinear and linear dampers have the advantage of allowing full recentring of the structure at the end of the seismic events, thus significantly improving resilience.

      PubDate: 2017-03-27T13:17:23Z
      DOI: 10.1016/j.soildyn.2017.03.023
      Issue No: Vol. 97 (2017)
       
  • Investigation on the seismic performance of steel-strip reinforced-soil
           retaining walls using shaking table test
    • Authors: M. Yazdandoust
      Pages: 216 - 232
      Abstract: Publication date: June 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 97
      Author(s): M. Yazdandoust
      The widespread use of reinforced-soil walls, especially in seismic regions has led to extensive studies on seismic behavior of this structures. In this paper, to assess the behavior and performance of steel-strip reinforced-soil retaining walls during seismic loading, a series of 1-g shaking table tests were conducted on 0.9m high reinforced-soil wall models with different strip lengths. The physical models were subjected to variable-amplitude harmonic excitation at different peak accelerations and durations. It was found that the deformation mode of walls highly depends on the length of strips. The observed predominant mode of deformation was combination of bulging of the facing and rotation about the wall base without base sliding. The pattern of the observed failure mechanisms included a moving block which is delineated by a combination of a slant and reverse curve with certain intersection point. Irrespective of different steel strip lengths, the threshold acceleration corresponding to the onset of plastic displacements was similar and equal to 0.6g for all models and the threshold acceleration corresponding to the onset of the development of active wedge failure was dependent on strip length so that this critical acceleration increased with increasing the strip length. Also, a consistent range of ∆x/H' between 0.2% and 0.8% (or ∆x/H'=0.2–0.8%) representing a transitional state of the walls from quasi-elastic to plastic state and a consistent range of ∆x/H' between 4.5% and 4.9% (or ∆x/H'=4.5–4.9%) representing a transitional state of the walls from plastic to failure state were observed. On the other hand, according to the sudden increase in wall displacements caused by decreasing the nail length from 0.7H' to 0.5H', the L/H' ratio of 0.7 was presented as the critical ratio in seismic conditions.

      PubDate: 2017-03-27T13:17:23Z
      DOI: 10.1016/j.soildyn.2017.03.011
      Issue No: Vol. 97 (2017)
       
  • Extraction of the 1D Green's function in a layered medium by three
           interferometry techniques: Theory and a case study
    • Authors: Carlos O. Jiménez-González; Juan A. Vazquez-Feijoo; Guillermo Urriolagoitia Sosa; Beatriz Romero Angeles; Andrés Pech Pérez
      Pages: 233 - 240
      Abstract: Publication date: June 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 97
      Author(s): Carlos O. Jiménez-González, Juan A. Vazquez-Feijoo, Guillermo Urriolagoitia Sosa, Beatriz Romero Angeles, Andrés Pech Pérez
      This paper presents a comparison of three interferometry techniques; cross-correlation, deconvolution and cross-coherency, when applied on a theoretical model of a layered medium. Explicit equations for the interferometry wavefields are obtained from the equations that govern displacements in a single-layered medium under the incidence of a plane SH-wave. A propagation matrix is developed in order to calculate the deconvolved wavefield in a medium with N layers without the need to know the displacement equations. It is herein demonstrated that cross-coherency is equivalent to the sign function of deconvolution; applied on deconvolved wavefields the cross-coherency is obtained by using the propagation matrix. The interferometry response from seismic data in the Roma C borehole localized in the valley of Mexico is compared with the theoretical response generated with the geological profile of the borehole, by deconovolution and cross-coherency.

      PubDate: 2017-03-27T13:17:23Z
      DOI: 10.1016/j.soildyn.2017.03.007
      Issue No: Vol. 97 (2017)
       
  • Settlement evaluation of explosive compaction in saturated sands
    • Authors: Reza Daryaei; Abolfazl Eslami
      Pages: 241 - 250
      Abstract: Publication date: June 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 97
      Author(s): Reza Daryaei, Abolfazl Eslami
      Explosive Compaction (EC) or Blast Densification (BD) has been commonly used as one of the deep soil improvement techniques to densify loose, saturated granular soils. Soil is compacted due to huge compression force of explosion in several depths and the corresponding liquefaction. Among soil characteristics, settlement is important since it is a fast and easy indicator of layer compaction degree. To measure settlement instrumentation can be used but they are expensive and susceptible to damage due to explosion. Predicting settlement using empirical equations is also another method, however, they cannot consider soil complex behavior and are consequently inaccurate. In this study, numerical approach has been used to evaluate settlement and excess pore water pressure (PWP) during and after explosion, using finite element software PLAXIS3D, in which the UBCSAND soil model has been employed to represent saturated sand. This model is capable of calculating PWP buildup due to dynamic loads such as earthquake and explosion. This method was calibrated and compared, using well-known case histories in the literature. Results of settlement from these cases, were compared with both empirical equations and measured site values. Pulses of PWP due to shock wave were also calculated by the model as well as PWP buildup until reaching liquefaction zone. Predictions from this approach were more accurate than empirical equations. Moreover, it was revealed that the rate of settlement and PWP dissipation is proportionate to soil's permeability. Thus, numerical approach can be confidently implemented to evaluate soil characteristics.

      PubDate: 2017-03-27T13:17:23Z
      DOI: 10.1016/j.soildyn.2017.03.015
      Issue No: Vol. 97 (2017)
       
  • Dynamic soil structure interaction of bridge piers supported on well
           foundation
    • Authors: Indrajit Chowdhury; Ronkoyel Tarafdar; Ambarish Ghosh; Sambhu P. Dasgupta
      Pages: 251 - 265
      Abstract: Publication date: June 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 97
      Author(s): Indrajit Chowdhury, Ronkoyel Tarafdar, Ambarish Ghosh, Sambhu P. Dasgupta
      For both steel and RCC Bridges passing rivers or creeks, common practice in many countries is to provide concrete wells to support the bridge girders. For many bridges that are strategically important in terms of defense or trade, it is essential that they remain functional even after a strong earthquake hits the structure. The present state of the art for design of well foundation is still marred with a number of uncertainties where a simplistic pseudo static analysis of its response only prevails, though it is a well-known fact that loads from super structure, character of soil and its stiffness plays an important role in defining its dynamic characteristics. The present paper is thus an attempt to present a dynamic analysis model trying to cater to a number of such deficiencies as cited above and also provide a practical model (amenable to design office application) that can be used to estimate the pier, well and soil's dynamic interaction

      PubDate: 2017-03-27T13:17:23Z
      DOI: 10.1016/j.soildyn.2017.03.005
      Issue No: Vol. 97 (2017)
       
  • Influence of air injection on the liquefaction-induced deformation
           mechanisms beneath shallow foundations
    • Authors: A. Zeybek; S.P.G. Madabhushi
      Pages: 266 - 276
      Abstract: Publication date: June 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 97
      Author(s): A. Zeybek, S.P.G. Madabhushi
      Earthquake-induced liquefaction of soils frequently causes serious damage to structures with shallow foundations. Reducing the degree of saturation of liquefiable soils by air injection is offered as a cost-effective and reliable method of mitigating liquefaction hazards. Nevertheless, very little experimental research is available on the performance of this method. Particularly, the way that air injection influences the deformation mechanisms beneath shallow foundations is not well defined. Gaining a deeper insight into soil displacements during and after air injection can pave the way for developing effective guidelines for the use of this particular technique. For this purpose, a series of dynamic centrifuge tests are presented in this paper. The prevailing deformation mechanisms are identified in a novel way using displacement vector fields. The results indicate that air injection alters the deformation mechanisms that develop underneath and in the ground surrounding a shallow foundation, substantially reducing the average settlements.

      PubDate: 2017-03-27T13:17:23Z
      DOI: 10.1016/j.soildyn.2017.03.018
      Issue No: Vol. 97 (2017)
       
  • Simplified probabilistic seismic assessment of RC frames with added
           viscous dampers
    • Authors: Luca Landi; Cristina Vorabbi; Omar Fabbri; Pier Paolo Diotallevi
      Pages: 277 - 288
      Abstract: Publication date: June 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 97
      Author(s): Luca Landi, Cristina Vorabbi, Omar Fabbri, Pier Paolo Diotallevi
      The object of this paper is the study of simplified probabilistic procedures for the seismic assessment of nonlinear structures equipped with nonlinear fluid viscous dampers. The considered reference probabilistic approach is the SAC-FEMA method, which allows to obtain the probability of exceeding a given performance level. The specific purpose is to study the correlation between the results obtained through the probabilistic seismic assessment method for structures with and without dampers, with emphasis on these results in terms of dispersion. A wide set of recorded ground motions was therefore selected and applied to the considered RC frames. The study was performed without applying scaling factors to the earthquake records, but by selecting different sets of records for increasing values of seismic intensity. All the obtained results were examined considering different criteria, in order to determine the set of time-history analyses to be used for the probabilistic evaluation. Different methods were then applied to obtain the dispersion of the seismic demand. With reference to the application of the SAC-FEMA method, a sensitivity analysis was also performed, considering different procedures to interpolate the hazard curve. From the analyses, it was possible to derive the expressions that allow the results for structures with and without dampers to be correlated, as well as to offer suggestions for applying the SAC-FEMA method. A second purpose of the paper is to propose and apply, in the probabilistic assessment, a direct procedure. This procedure was recently presented by some of the authors as a method to be used for obtaining the response of nonlinear structures with nonlinear viscous dampers as an alternative to expensive nonlinear dynamic analyses.

      PubDate: 2017-03-27T13:17:23Z
      DOI: 10.1016/j.soildyn.2017.03.003
      Issue No: Vol. 97 (2017)
       
  • Near-field effects on site characterization using MASW technique
    • Authors: Narayan Roy; Ravi S. Jakka
      Pages: 289 - 303
      Abstract: Publication date: June 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 97
      Author(s): Narayan Roy, Ravi S. Jakka
      The application of Multichannel Analysis of Surface Wave (MASW) technique is increasing in geotechnical engineering to characterize near surface materials. The dispersion property of Rayleigh wave is utilized in MASW method. MASW often suffers from near-field effects which may result in either underestimation or overestimation of Rayleigh wave phase velocity due to the body waves contamination near to the source. In this paper, a detailed numerical study has been carried out to examine the near-field effects considering three different types of typical S-wave velocity models with four different impedance scenarios in each case. The study shows that the impedance contrast between the half-space and overlying soil layer is having a considerable effect on the underestimation of phase velocity. These near-field effects are also found to be influenced by the type of the S-wave velocity model as well as far and near offset distances. With the increase of impedance contrast, the level of underestimation seems to increase at lower normalized array centre distance due to mode jump. However, such jump can not be observed with limited far offset distances generally used in usual practice due to poor resolution in the dispersion spectra. Significant near-field effect are observed for lower far offset distances and inversely dispersive S-wave velocity models. Underestimation of Rayleigh wave phase velocity is quantified in terms of two normalized parameters. Finally, a field study is also conducted to verify our numerical findings.

      PubDate: 2017-03-27T13:17:23Z
      DOI: 10.1016/j.soildyn.2017.02.011
      Issue No: Vol. 97 (2017)
       
  • Centrifuge modeling of mitigation-soil-foundation-structure interaction on
           liquefiable ground
    • Authors: J. Olarte; B. Paramasivam; S. Dashti; A. Liel; J. Zannin
      Pages: 304 - 323
      Abstract: Publication date: June 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 97
      Author(s): J. Olarte, B. Paramasivam, S. Dashti, A. Liel, J. Zannin
      Significant progress has been made in recent years toward a better understanding of the liquefaction phenomena. Yet, the combined effects of excess pore pressure generation, permanent soil deformation, and ground shaking, with and without mitigation, on the performance of the soil-foundation-structure system remain poorly understood. Moreover, there is a lack of physical model studies incorporating these important effects for a range of conditions to validate numerical models. This paper presents an experimental study of the performance of 3-story structures with shallow foundations on a saturated soil profile including a thin liquefiable layer. The influence of three different mitigation techniques was evaluated: 1) ground densification; 2) enhanced drainage with prefabricated vertical drains (PVDs); and 3) reinforcement with in-ground structural walls. Densification was observed to slightly reduce excess pore pressures and permanent foundation settlement and tilt, but amplified the demand transferred to the superstructure. Use of PVDs reduced permanent foundation settlement and rotation by reducing the duration of large excess pore pressures, but amplified roof accelerations and flexural drift. The performance of the stiff structural wall depended on the properties of the earthquake motion. During more intense, longer-duration motions, confining the soil and inhibiting flow inside the structural wall led to liquefaction, larger settlements, and larger translational and rotational accelerations on the foundation. In this case, the dissipation of seismic energy through additional foundation movements reduced the moment-rotation demand on the columns. These experimental results emphasize the importance of evaluating the potential tradeoffs of liquefaction mitigation, which may reduce settlement and sometimes tilt, but result in larger transient drifts and damage to the superstructure.

      PubDate: 2017-03-27T13:17:23Z
      DOI: 10.1016/j.soildyn.2017.03.014
      Issue No: Vol. 97 (2017)
       
  • Track-ground vibrations induced by railway traffic: experimental
           validation of a 3D numerical model
    • Authors: N. Correia dos Santos; J. Barbosa; R. Calçada; R. Delgado
      Pages: 324 - 344
      Abstract: Publication date: June 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 97
      Author(s): N. Correia dos Santos, J. Barbosa, R. Calçada, R. Delgado
      This paper presents a numerical model that can be used to perform a fully three-dimensional analysis of problems involving vibrations induced by railway traffic, taking into account the dynamic interaction of the vehicle-structure-ground system. The structure and the vehicle are modelled with finite elements, while the behaviour of the ground is described by its Green's functions. It is a particular case of a FEM/BEM coupling, in the time domain, wherein the structure modelled with finite elements lays on the surface of the ground. The dynamic analysis of the system results from the direct and efficient calculation of a single system of equations. The validation of the proposed model is based on the results of an experimental campaign developed in a stretch of the Portuguese railway network. The vibrations generated by one passage of the Alfa Pendular train are analysed and a good agreement between measured and calculated responses is achieved.

      PubDate: 2017-03-27T13:17:23Z
      DOI: 10.1016/j.soildyn.2017.03.004
      Issue No: Vol. 97 (2017)
       
  • Safety evaluation of cored rockfill dams under high seismicity using
           dynamic centrifuge modeling
    • Authors: Dong Soon Park; Nam-Ryong Kim
      Pages: 345 - 363
      Abstract: Publication date: June 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 97
      Author(s): Dong Soon Park, Nam-Ryong Kim
      Dynamic centrifuge modeling was performed for inclined-core rockfill dams under high seismicity to assess their seismic safety and characterize the dynamic response of embankments. Latest techniques including two-stage generalized scaling, shell stiffness matching, and single target g-level shaking were adopted. The effect of rockfill material degradation on the seismic response was investigated. All the inclined-core rockfill dam models indicated that exceptionally strong shaking (0.7–1.0g) does not endanger structural safety although the less competent shell models undergo comparable deformation. Measured data indicated that a counterbalancing effect influences the seismic response of dam models: increased damping from shear strains (material nonlinearity) and amplification from material inhomogeneity. An irregular stiff foundation is believed to affect the attenuation characteristics of motion. The study results/data will contribute to the research of advanced physical modeling of large embankments under seismic areas and help to validate the procedures and results of numerical modeling.

      PubDate: 2017-03-27T13:17:23Z
      DOI: 10.1016/j.soildyn.2017.03.020
      Issue No: Vol. 97 (2017)
       
  • A completely explicit finite element method for solving dynamic u-p
           equations of fluid-saturated porous media
    • Authors: Chengshun Xu; Jia Song; Xiuli Du; Zilan Zhong
      Pages: 364 - 376
      Abstract: Publication date: June 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 97
      Author(s): Chengshun Xu, Jia Song, Xiuli Du, Zilan Zhong
      A completely explicit finite element method is developed to efficiently solve the dynamic u -p equations of fluid-saturated porous media (FSPM). In the spatial domain, a diagonalization method is applied to both the mass and the fluid compressibility matrices by neglecting the interactions between adjacent nodes in the finite element model of FSPM for the first time. In the time domain, an explicit-explicit algorithm consisting of the central and the unilateral difference methods is applied to solve the dynamic u-p equations. The stability and accuracy of the proposed explicit-explicit algorithm are discussed. Moreover, five numerical examples were presented in this paper. The good agreements between the results obtained from the proposed method and the existing explicit-implicit method indicate that the diagonalization method for the fluid compressibility matrix and the proposed completely explicit method are validity in solving the dynamic u -p equations of FSPM.

      PubDate: 2017-03-27T13:17:23Z
      DOI: 10.1016/j.soildyn.2017.03.016
      Issue No: Vol. 97 (2017)
       
  • A combined numerical/experimental prediction method for urban railway
           vibration
    • Authors: Georges Kouroussis; Konstantinos E. Vogiatzis; David P. Connolly
      Pages: 377 - 386
      Abstract: Publication date: June 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 97
      Author(s): Georges Kouroussis, Konstantinos E. Vogiatzis, David P. Connolly
      Railway-induced ground vibrations can cause negative effects to people/structures located in urban areas. One of the main sources of these vibrations is from the large vehicle forces generated when train wheels impact local defects (e.g. switches/crossings). The sole use of traditional in-field transfer-mobility approaches is well suited for plain-line assessments, however is more challenging when discontinuities are present, due to the generation of large magnitude impact forces. This paper presents a hybrid experimental-numerical approach that can predict ground-borne vibration levels in the presence of a variety of railroad artefacts such as transition zones, switches, crossings and rail joints on existing networks. Firstly, the experimental procedure is described, which consists of multiple single source transfer mobilities to determine the transmission characteristics between rail and nearby structures. This is then coupled with a combined multibody vehicle and track numerical model, which is capable of simulating vibration generation in the presence of railway discontinuities. The resulting model is advantageous over alternative approaches because it can account for complex railway discontinuities, while at the same time incorporating the large uncertainties associated with different soil configurations. It is used to analyse a case study, where it is shown that vibration levels are strongly dependent on vehicle speed, defect type and defect size.

      PubDate: 2017-04-03T23:03:46Z
      DOI: 10.1016/j.soildyn.2017.03.030
      Issue No: Vol. 97 (2017)
       
  • Dynamic impedance of a pipe pile in layered soils under vertical
           excitations
    • Authors: Zhi Yong Ai; Chun Lin Liu
      Pages: 387 - 394
      Abstract: Publication date: June 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 97
      Author(s): Zhi Yong Ai, Chun Lin Liu
      This paper investigates the dynamic impedance of a vertically loaded pipe pile embedded in layered soils. The dynamic response of pipe piles is governed by the 1D vibration theory, which is formulated as a series of matrix equations. Meanwhile, the dynamic solution for layered soils is achieved by the application of the stiffness matrix deduced from the analytical layer-element method. Based on the displacement compatibility and traction equilibrium at the interface between the pipe pile and both inner and outer soils, the dynamic pipe pile-soil interaction equations are established and solved efficiently. The validity and accuracy of the proposed method are demonstrated by the solutions of vertical impedances of a solid pile and a pipe pile embedded in a homogeneous half-space. Some numerical results are presented to explore the effects of wall thickness, length-radius ratio and layering of soils on the vertical impedances of pipe piles.

      PubDate: 2017-04-03T23:03:46Z
      DOI: 10.1016/j.soildyn.2017.03.029
      Issue No: Vol. 97 (2017)
       
  • Seismic microzoning of Belgrade
    • Authors: V.W. Lee; M.D. Trifunac; B.Đ. Bulajić; M.I. Manić; D. Herak; M. Herak
      Pages: 395 - 412
      Abstract: Publication date: June 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 97
      Author(s): V.W. Lee, M.D. Trifunac, B.Đ. Bulajić, M.I. Manić, D. Herak, M. Herak
      Seismic microzonation maps for Belgrade (Serbia) and its surroundings are presented based on the uniform-hazard-spectrum (UHS) methodology. Such mapping must satisfy the guidelines for performance-based design (PBD), which at present requires the specification of two sets of spectral amplitudes, one in which the structure would remain essentially linear, and one in which it would undergo nonlinear response. These requirements cannot be achieved by specifying the design spectra using only one (same) fixed spectral shape, and such spectra cannot be scaled by the peak ground acceleration alone. Another source of difficulties in the selection of the design amplitudes for PBD occurs when the standard spectrum shape is not capable of describing excitation by large, distant earthquakes. Furthermore, scaling the site dependent design ground motion only via soil site classification ignores the effects of site geology and thus leads to biased results. The maps we present in this paper avoid these shortcomings and include the effects of near and distant large earthquakes, spatial distribution of seismic activity, site geology, and site soil properties in a balanced way.

      PubDate: 2017-04-03T23:03:46Z
      DOI: 10.1016/j.soildyn.2017.02.002
      Issue No: Vol. 97 (2017)
       
  • Hypoelastic UR-free model for soils under cyclic loading
    • Authors: João Camões Lourenço; Jaime Alberto dos Santos; Pedro Pinto
      Pages: 413 - 423
      Abstract: Publication date: June 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 97
      Author(s): João Camões Lourenço, Jaime Alberto dos Santos, Pedro Pinto
      The study of problems that deal with soil behaviour under seismic loading conditions requires the use of a constitutive model able to reproduce the cyclic behaviour of soils from small strains to failure. Models commonly used when modelling soils at small to medium strain domain, for certain cyclic loading scenarios, are based on non-linear elasticity of the stress-strain relationship. These models have a group of rules to define first loading behaviour and to define unloading and reloading behaviour. Most models of this type rely on non-linear backbone functions and adopt Masing rule, having fixed formulas with a limited set of parameters, which are calibrated to adapt to experimental testing data. However, being these functions dependent on fixed formulas, makes them somewhat inflexible and hard to adapt to some experimental data. The objective of this work was the development of two simple but flexible non-linear elastic soil models that, given strain-dependent modulus and damping results from laboratory tests, could be easily calibrated: Hypoelastic spline based model and Hypoelastic UR-free model. The mathematical formulation is explained, the capability to describe peculiar soils behaviours is proved and an implementation in a FEM code is presented and discussed.

      PubDate: 2017-04-03T23:03:46Z
      DOI: 10.1016/j.soildyn.2017.03.009
      Issue No: Vol. 97 (2017)
       
  • An analytical solution for the rotational component of the Foundation
           Input Motion induced by a pile group
    • Authors: Raffaele Di Laora; Yado Grossi; Luca de Sanctis; Giulia M.B. Viggiani
      Pages: 424 - 438
      Abstract: Publication date: June 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 97
      Author(s): Raffaele Di Laora, Yado Grossi, Luca de Sanctis, Giulia M.B. Viggiani
      This work investigates the effect of the rotational component of input motion induced by the kinematic interaction between a pile group and the surrounding soil on the seismic behaviour of a structure. To this end, a simple analytical model is developed by deriving the pile group behaviour from the seismic response of a single pile, taking into account equilibrium and compatibility of displacements at piles’ heads. Closed-form solutions in the frequency domain are provided for both the translational and the rotational motion of a group of unevenly distributed identical piles, rigidly connected at the top and displaced by the surrounding soil, which is subjected to purely translational oscillations. The proposed solutions, applicable to any subsoil conditions, highlight that pile group layout is the crucial parameter governing the magnitude of the foundation rotation. Further, new transfer functions from the soil surface in free field conditions to the top of a SDOF system are introduced, which take into account the translational and/or rotational kinematic effects. An application of the above concepts to a case study is presented, highlighting that the rotational component of input motion may be important for tall structures on small pile groups.

      PubDate: 2017-04-10T23:14:28Z
      DOI: 10.1016/j.soildyn.2017.03.027
      Issue No: Vol. 97 (2017)
       
  • Deformation mechanisms for offshore monopile foundations accounting for
           cyclic mobility effects
    • Authors: A. Barari; M. Bagheri; M. Rouainia; L.B. Ibsen
      Pages: 439 - 453
      Abstract: Publication date: June 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 97
      Author(s): A. Barari, M. Bagheri, M. Rouainia, L.B. Ibsen
      There has been a huge surge in the construction of marine facilities (e.g., wind turbines) in Europe, despite the many unknowns regarding their long-term performance. This paper presents a new framework for design strategy based on performance measures for cyclic horizontally loaded monopile foundations located in saturated and dry dense sand, by considering pile deformations and pore pressure accumulation effects. A three-dimensional finite element model was developed to investigate the behavior of large-diameter piles. The model accounts for nonlinear dynamic interactions in offshore platforms under harsh combined moment and horizontal environmental loads, with emphasis on the cyclic mobility of the surrounding cohesionless subsoil and associated shear. The maximum moment applied in the cyclic analyses is varied from 18% to 47% of the ultimate resistance. The considered data reflect behavior at the expected load amplitudes and cycle numbers during the service life of operation. For low numbers of load cycles (<1000 cycles), there were no differences between the power law and logarithmic approaches in terms of describing the accumulated deformations; however, for high numbers of cycles (<10,000 cycles), the logarithmic law was less suited to describe the accumulation response. Magnitude of cyclic loads was found to cause a linear increase in the accumulated rotation. The results from short-term and long-term dynamic response of monopiles indicate that few load cycles with higher load levels are the main concerns in accumulation of pile rotation rather than thousands of load cycles with low amplitudes.

      PubDate: 2017-04-10T23:14:28Z
      DOI: 10.1016/j.soildyn.2017.03.008
      Issue No: Vol. 97 (2017)
       
  • Dynamic pile impedances for fixed-tip piles
    • Authors: George Anoyatis; Raffaele Di Laora; Anne Lemnitzer
      Pages: 454 - 467
      Abstract: Publication date: June 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 97
      Author(s): George Anoyatis, Raffaele Di Laora, Anne Lemnitzer
      The behavior of a laterally loaded pile with fixed-tip boundary condition (i.e., displacement and rotation, are perfectly restrained) is evaluated using a recently proposed, improved Tajimi-type model. The model performance in both, static and dynamic regime is first validated against rigorous finite element solutions and subsequently compared with Winkler model results for a selected range of pile-soil system parameters. In addition, pile impedances for fixed-tip piles are compared with previously proposed impedance expressions for hinged-tip piles. Results indicate that pile tip fixity has moderate impact on the pile stiffness in rotation but show stronger influence for pile stiffness in swaying and cross-swaying. The effect of tip fixity on pile impedances diminishes when piles are longer than approximately ten pile diameters. The proposed expressions for damping were evaluated across a wide range of frequencies, and damping was found to be most pronounced in rotation across the entire spectrum of pile-soil stiffness ratios examined. Winkler based formulations from literature almost exclusively over-predict damping for fixed tip piles.

      PubDate: 2017-04-10T23:14:28Z
      DOI: 10.1016/j.soildyn.2017.03.025
      Issue No: Vol. 97 (2017)
       
  • Approximate solution for seismic earth pressures on rigid walls retaining
           inhomogeneous elastic soil
    • Authors: Scott J. Brandenberg; George Mylonakis; Jonathan P. Stewart
      Pages: 468 - 477
      Abstract: Publication date: June 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 97
      Author(s): Scott J. Brandenberg, George Mylonakis, Jonathan P. Stewart
      An approximate elasto-dynamic solution is developed for computing seismic earth pressures acting on rigid walls retaining continuously inhomogeneous elastic material and excited by vertically propagating shear waves. The shear modulus of the soil is represented as a nonlinear function of depth, in a manner that is consistent with established analytical and empirical relationships, while mass density and Poisson's ratio are assumed constant. Solutions are presented for a single wall and for a pair of walls spaced at a finite distance. A shape function characterizing the vertical variation of horizontal displacement of the soil column in the free-field is assigned, and simplifying assumptions regarding the dynamic vertical stresses and the vertical-to-horizontal displacement gradient are made to facilitate closed-form expressions for horizontal displacement and stress fields. These solutions are used to compute the distribution of dynamic horizontal earth pressure acting on the wall. A Winkler stiffness intensity relationship is then derived such that the proposed method can be extended beyond the boundary conditions considered herein. These solutions agree well with exact analytical elasto-dynamic solutions for inhomogeneous soil that are considerably more complicated to implement. Causes of differences between the solutions are discussed.

      PubDate: 2017-04-10T23:14:28Z
      DOI: 10.1016/j.soildyn.2017.03.028
      Issue No: Vol. 97 (2017)
       
  • A practical method for construction of p-y curves for liquefiable soils
    • Authors: Suresh Dash; Mehdi Rouholamin; Domenico Lombardi; Subhamoy Bhattacharya
      Pages: 478 - 481
      Abstract: Publication date: June 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 97
      Author(s): Suresh Dash, Mehdi Rouholamin, Domenico Lombardi, Subhamoy Bhattacharya
      In practice, the analysis of laterally loaded piles is often carried out using a “Beam on Non-linear Winkler Foundation method” whereby the lateral pile-soil interaction is modelled as a set of non-linear springs (also known as p-y curves). During seismic liquefaction, the saturated sandy soil changes its state from a solid to a viscous fluid like material, which in turn alters the shape of the p-y curve. Typically, p-y curves for non-liquefied soil looks like a convex curve with an initial stiff slope that reduces with increasing pile-soil relative displacement (y) i.e., elasto-plastic softening response. However, recent research conclusively showed that p-y curve for liquefied soil has a different shape, i.e., upward concave with practically-zero initial stiffness (due to the loss of particle to particle contact) up to a certain displacement, beyond which the stiffness increases due to reengaging of the sand particles. This paper presents a practical method for construction of the newly proposed p-y curves along with an example.

      PubDate: 2017-04-10T23:14:28Z
      DOI: 10.1016/j.soildyn.2017.03.002
      Issue No: Vol. 97 (2017)
       
  • A nonlinear approach for the three-dimensional polyhedron scaled boundary
           finite element method and its verification using Koyna gravity dam
    • Authors: Kai Chen; Degao Zou; Xianjing Kong
      Pages: 1 - 12
      Abstract: Publication date: May 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 96
      Author(s): Kai Chen, Degao Zou, Xianjing Kong
      Since it was presented, the scaled boundary finite element method (SBFEM) has been shown to be versatile and has been widely applied in structural numerical simulations. However, as it is analytical in the radial direction, nonlinearity inside elements cannot be considered, limiting its application in elastic fields. In this paper, a nonlinear approach for the three-dimensional polyhedron scaled boundary finite element (NPSBFEM3D) is proposed for elasto-plastic analysis to remove this restriction. In NPSBFEM3D, conforming shape functions are constructed using the semi-analytical solution derived from elastic surface elements, while the integrations are accomplished using internal Gauss points in the radial direction instead of integrating on the boundary surface elements. Eventually, the proposed approach can be as conveniently used in elasto-plastic analysis as FEM. This method permits an arbitrary number of faces, which offers a promising adaptive capacity for modelling. Three simulations are conducted to verify the robustness of the presented method.

      PubDate: 2017-02-17T02:23:08Z
      DOI: 10.1016/j.soildyn.2017.01.028
      Issue No: Vol. 96 (2017)
       
  • Editorial Board / Aims and Scope
    • Abstract: Publication date: May 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 96


      PubDate: 2017-03-27T13:17:23Z
       
 
 
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