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Journal Cover Soil Dynamics and Earthquake Engineering
  [SJR: 1.482]   [H-I: 45]   [7 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0267-7261
   Published by Elsevier Homepage  [2817 journals]
  • Preliminary empirical scaling of pseudo relative velocity spectra in
           Serbia from the Vrancea earthquakes
    • Abstract: Publication date: July 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 86
      Author(s): V.W. Lee, M.D. Trifunac, B.Đ. Bulajić, M.I. Manić
      First frequency-dependent empirical scaling equations of pseudo-relative velocity spectral amplitudes (PSV) of strong earthquake ground motions in the former Yugoslavia were introduced in the mid-1990s by Lee and Trifunac (1990) [15]. This followed the development of the Fourier spectral amplitudes (FS) scaling equations by Lee and Trifunac (1993) [17] in terms of earthquake source parameters, and the region-specific frequency dependent attenuation function given by Lee and Trifunac (1992) [16]. More recently, a new frequency-dependent attenuation function was developed for central and eastern Serbia for earthquakes of intermediate and large magnitudes and for large epicentral distances—exceeding 300km—suggested by Lee et al. (2016) [19] that occur in the Vrancea source region in Romania. In this paper we use this frequency-dependent attenuation function to develop empirical scaling equations for PSV spectral amplitudes in Serbia. These scaling equations will form a basis for macro- and micro-zoning earthquake hazard studies in Serbia.


      PubDate: 2016-04-29T13:14:02Z
       
  • Small-strain shear modulus of volcanic granular soil: An experimental
           investigation
    • Abstract: Publication date: July 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 86
      Author(s): Xin Liu, Jun Yang, Gonghui Wang, Longzhu Chen
      While volcanic soils exist in many places around the world, their mechanical behavior is however less extensively studied as compared to the conventional soil type such as quartz sand and clay. This paper presents an experimental study investigating the small-strain shear modulus (G 0) and associated shear wave velocity (V s) of a volcanic granular soil collected from the northeast of Japan that was affected by the devastating 2011 Tohoku earthquake. Reconstituted soil specimens were tested at different packing densities and confining stress levels by using the resonant column technique, and the pressure and density dependence of shear modulus was established for the soil. The study showed that under otherwise similar conditions, the G 0 value of the volcanic soil was markedly lower than that of clean quartz sands, but it tended to increase significantly when the fine particles in the soil were removed. This finding suggests that the presence of fines plays an important role in the mechanical behavior of volcanic soils. A practical model accounting for the influence of fines and the pressure and density dependence is proposed and it is shown to provide reasonable estimates of G 0 for both volcanic soils and clean quartz sands studied.


      PubDate: 2016-04-29T13:14:02Z
       
  • An analytical model for vibration prediction of a tunnel embedded in a
           saturated full-space to a harmonic point load
    • Abstract: Publication date: July 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 86
      Author(s): Zonghao Yuan, Yuanqiang Cai, Zhigang Cao
      The dynamic response of a tunnel embedded in a saturated poroelastic full-space under a vertical harmonic load was investigated by a semi-analytical method. The tunnel was modeled as a thin cylindrical shell surrounded by soil of infinite radial extent. The soil was modeled as a saturated poroelastic full-space. Biot's theory was applied to characterize the soil medium, taking the solid skeleton-pore fluid coupling effects into account. Combined with the boundary conditions at tunnel–soil interface, the coupled equations of the system were solved in the frequency domain with the aid of Fourier decomposition and Fourier transform in the circumferential and longitudinal direction, respectively. Dynamic responses of the tunnel and soil generated by a unit harmonic load applied at the tunnel invert are presented. It is found that the soil permeability and the load frequency have significant influence on the displacements, the stresses and the pore pressure in the saturated soil. In the free field, an increase of the soil permeability leads to a decrease of the soil displacement and pore pressure response. An equivalent single-phase material was used to model the saturated soil and it is found only applicable for soil with lower permeability.


      PubDate: 2016-04-29T13:14:02Z
       
  • Experimental and finite element study of the reverse faulting effects on
           buried continuous steel gas pipelines
    • Abstract: Publication date: July 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 86
      Author(s): Himan Hojat Jalali, Fayaz Rahimzadeh Rofooei, Nader Khajeh Ahmad Attari, Masoud Samadian
      Permanent ground displacement (PGD) caused by surface faulting is considered as one of the most significant hazards affecting buried pipelines. Pipelines crossing reverse-slip faults are subjected to compressive actions (stresses and strains) which can result in buckling of the pipe. In current work, the results obtained from the full-scale laboratory testing and finite element analyses of 4″ (114.3mm) and 6″ (168.3mm) steel gas pipes (without internal pressure) buried inside a split box and subjected to a reverse faulting of 0.6m (pure dip-slip) are presented. These pipes are commonly used in gas distribution lines and networks. The experimental setup, procedure and instrumentation as well as the finite element (FE) modeling of the problem are described in detail. It is observed that the soil failure in the moving part of the split-box occurs along vertical surfaces extending from the sides of the pipe to the ground surface. The experimental results indicate that both pipes exhibit an S-shape deformation with two local buckling sections where the excessive yielding and plastic deformations of the pipes could lead to rupture failure. Both pipes exhibited “diamond-shape” buckled sections. The buckled sections of the pipes in the fixed and moving parts of the split box were unsymmetrical with respect to the fault plane. Using the factor of ovality to measure the pipe cross-section distortion, it is found that the cross-section distortion is more severe for the buckled section of the pipe in the moving part of the split box in comparison to its fixed part. Also, the distance between the buckled sections increases by increasing the pipe diameter, while the distortion of the pipe cross-section increases by increasing the pipe diameter over thickness ratio. Using the FE models that were validated utilizing the experimental results, the maximum equivalent soil–pipe interaction forces and their distribution along the pipes were determined and the results were compared with that of American Lifeline Alliance Guidelines for the Design of Buried Steel Pipe (ALA, 2005) [33]. The obtained maximum bearing force is less than the suggested values by ALA, while the maximum uplift force slightly exceeds those of ALA. The results indicate that for the considered cases, the uplift force is sensitive to the pipe diameter and its relative stiffness, while the ALA (2005, [33]) suggests a constant force for the burial depths considered in this study.


      PubDate: 2016-04-29T13:14:02Z
       
  • Analysis of the effect of groundwater level on the seismic behavior of an
           unsaturated embankment on clayey ground
    • Abstract: Publication date: June 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 85
      Author(s): Takahiro Yoshikawa, Toshihiro Noda, Takeshi Kodaka, Toshihiro Takaine
      Numerous river levees on clayey soil grounds were damaged by the 2011 off the Pacific coast of Tohoku Earthquake. In order to investigate such damage, the behavior of an unsaturated embankment on clayey ground was simulated during its construction, during an earthquake and after the earthquake. The simulation was carried out using a soil–water–air coupled finite deformation analysis code, with attention being focused on the effect of groundwater level. The results indicated that if the groundwater level is high, a saturated area (settlement-induced saturation area) is formed at the base of the embankment due to penetrative settlement during/after construction. In addition, the mean skeleton stress is low compared with the low groundwater level. As a consequence, in the embankment on ground with the high groundwater level, the co-seismic deformation is greater and the mean skeleton stress decreases sharply, particularly in the settlement-induced saturation area during the earthquake. It was also shown that after the earthquake, the groundwater level rises because water flows toward the unsaturated embankment from the settlement-induced saturation area and/or the saturated clayey ground. If the groundwater level is high, in particular, a phreatic line is formed temporarily within the embankment.


      PubDate: 2016-04-24T12:56:51Z
       
  • A Discussion of the paper: “Ant colony optimization of tuned mass
           dampers for earthquake oscillations of high-rise structures including
           soil–structure interaction” [Soil Dyn. Earthq. Eng. 51 (2013)
           14–22]
    • Abstract: Publication date: Available online 18 April 2016
      Source:Soil Dynamics and Earthquake Engineering
      Author(s): Ali Reza Rahai, Hossein Saberi, Hassan Saberi
      This discussion is based on the paper by Farshidianfar and Soheili [1]. In this paper, the authors consider Soil–Structure Interaction effects (SSI) and optimize parameters of Tuned Mass Dampers (TMD) to decrease the earthquake vibrations of tall buildings. They also develop a mathematical model based on the time domain analysis. In this discussion we show that the offered model is not accurate enough and we rectify the model.


      PubDate: 2016-04-19T17:26:06Z
       
  • Seismic response of underground reservoir structures in sand: Evaluation
           of Class-C and C1 numerical simulations using centrifuge experiments
    • Abstract: Publication date: June 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 85
      Author(s): Y.H. Deng, S. Dashti, A. Hushmand, C. Davis, B. Hushmand
      Centrifuge experiments were conducted to investigate the seismic response of stiff-unyielding buried reservoir structures with varying stiffness in medium-dense, dry sand. The results of these tests were used to evaluate the predictive capabilities of Class-C and C1, nonlinear, finite element analyses of the seismic response of these relatively stiff buried structures. All simulations were performed in two dimensions using the pressure-dependent, multi-yield-surface, plasticity-based soil constitutive model (PDMY02) implemented in OpenSees. For Class-C simulations, model parameters were calibrated based on the available cyclic simple shear tests on the test soil. For Class-C1 simulations, the same soil model was used along with user-defined modulus reduction curves that were corrected for soil's implied shear strength. The use of shear modulus reduction curves, which modeled a softer soil response compared to PDMY02, generally improved the prediction of site response in the far-field as well as seismic racking deformations, earth pressures, and bending strains on the structures. Experimentally, the dynamic thrust, racking, and bending strains on or of the model structures were shown to primarily peak near the strain-dependent fundamental frequency of the site, regardless of the fundamental frequency of the structure itself. This influence in addition to other important response parameters were captured reasonably well by Class-C1 simulations, with residuals ranging from −0.25 to 0.2.


      PubDate: 2016-04-19T17:26:06Z
       
  • On the seismic stability and critical slip surface of reinforced slopes
    • Abstract: Publication date: June 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 85
      Author(s): M. Khosravizadeh, M. Dehestani, F. Kalantary
      Seismic stability of reinforced slopes is investigated using Horizontal Slice Method within the framework of the pseudo-static force. These introduced by constant horizontal or vertical inertial forces and the equilibrium equations for all forces applied to each horizontal slice are considered. A new procedure is introduced which could determine the location and shape of failure surface. The slip surface is a multiplanar surface consisting of a number of inclined linear segments interconnected with various lengths and angles in a plane. The amount of reinforcement forces is used as the objective function in the optimization procedure to determine the shape and location of the critical slip surface. This approach is relatively simple and yields results which are in good agreement with previous findings. Final results revealed that with increase in horizontal seismic acceleration, the reinforcements force increases. With increase in slope angle, the failure surface changes from curve to planar shape.


      PubDate: 2016-04-19T17:26:06Z
       
  • A refined analytical model for earthquake-induced sloshing in
           half–full deformable horizontal cylindrical liquid containers
    • Abstract: Publication date: June 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 85
      Author(s): Spyros A. Karamanos, Angeliki Kouka
      The coupled response of elastic deformable liquid containers of horizontal-cylindrical shape under external seismic excitation is examined, through an analytical methodology, assuming inviscid-incompressible fluid and irrotational-flow conditions. In particular, the case of a half–full horizontal-cylindrical deformable container is examined, considering an analytical series-type solution for the velocity potential function that describes the liquid motion under external excitation. This mathematical analysis extends the solution methodology presented in previous publications of the senior author, taking into account full coupling between sloshing and wall deformation in a rigorous manner, where wall deformation is considered through a sinusoidal assumed-shape function. In the mathematical formulation, the velocity potential is decomposed into three parts: (a) a first part, which represents liquid motion that follows the external excitation, (b) a “convective part”, representing liquid motion associated with free surface elevation (sloshing), and (c) a third part caused by the wall deformation. Using an elegant mathematical manipulation, the coupled transient overall response of the liquid-container system is obtained in an efficient manner. Numerical results are presented in terms of the principal natural frequencies of the coupled system, as well as the system response under strong seismic input, and emphasize on the effects of container aspect ratio on the dynamic behavior of the system. The mathematical formulation for the case of long cylinders results in a simplified model, identical to the simplified “physical model” presented in a previous publication.


      PubDate: 2016-04-19T17:26:06Z
       
  • A spatial correlation model of peak ground acceleration and response
           spectra based on data of the Istanbul Earthquake Rapid Response and Early
           Warning System
    • Abstract: Publication date: June 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 85
      Author(s): Thomas Wagener, Katsuichiro Goda, Mustafa Erdik, James Daniell, Friedemann Wenzel
      Ground motion intensity measures such as the peak ground acceleration (PGA) and the pseudo-spectral acceleration (PSA) at two sites due to the same seismic event are correlated. The spatial correlation needs to be considered when modeling ground-motion fields for seismic loss assessments, since it can have a significant influence on the statistical moments and probability distribution of aggregated seismic loss of a building portfolio. Empirical models of spatial correlation of ground motion intensity measures exist only for a few seismic regions in the world such as Japan, Taiwan and California, since for this purpose a dense observation network of earthquake ground motion is required. The Istanbul Earthquake Rapid Response and Early Warning System (IERREWS) provides one such dense array with station spacing of typically 2km in the urban area of Istanbul. Based on the records of eight small to moderate (M w3.5–M w5.1) events, which occurred since 2003 in the Marmara region, we establish a model of intra-event spatial correlation for PGA and PSA up to the natural period of 1.0s. The results indicate that the correlation coefficients of PGA and short-period PSA decay rapidly with increasing interstation distance, resulting in correlation lengths of approximately 3–4km, while correlation lengths at longer natural periods (above 0.5s) exceed 6km. Finally, we implement the correlation model in a Monte Carlo simulation to evaluate economic loss in Istanbul's district Zeytinburnu due to a M w7.2 scenario earthquake.


      PubDate: 2016-04-19T17:26:06Z
       
  • PGA-PGV/Vs considered as a stress–strain proxy for predicting
           nonlinear soil response
    • Abstract: Publication date: June 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 85
      Author(s): Johanes Chandra, Philippe Guéguen, Luis Fabian Bonilla
      In this paper, a relationship proxy for predicting the nonlinear soil responses is proposed by mean of monitoring the variation of shear wave velocity along vertical array. The recent seismic interferometry by deconvolution method is applied to extract the shear-wave velocity profile throughout the soil column. Using synthetic modeling, this method is shown to be a relevant and an efficient solution for assessing the Vs profile along a vertical seismic array. The ratio between particle velocity and the equivalent linear shear-wave velocity, v*/Vs*, is computed between two successive sensors, and is assumed to be a proxy for strain. The particle acceleration, a*, versus v*/Vs* is proposed as a stress–strain representation for nonlinear analysis of soil response. Using centrifuge tests, v*/Vs* is shown to be a good representation for soil strain, and analysis of the variation of v*/Vs* as a function of a* allows the nonlinear soil response to be determined in an earthquake situation. These relationship proxies are finally applied to the Japanese K-NET and KiK-net in-situ data, where Vs 30 is used instead of Vs* for practical purposes related to site classification recommendations.


      PubDate: 2016-04-19T17:26:06Z
       
  • A numerical and experimental study of hollow steel pile in layered soil
           subjected to vertical dynamic loading
    • Abstract: Publication date: June 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 85
      Author(s): D. Bhowmik, D.K. Baidya, S.P. Dasgupta
      This paper presents an investigation of the nonlinear behaviour of single piles subjected to varying levels of vertical dynamic load. A good number of tests are performed for the understanding of the dynamic behaviour of single hollow steel piles embedded in layered soil. Experimental results are validated with results obtained from a nonlinear numerical analysis using commercially available Finite Element Method (FEM) based software. The results of numerical analysis and experimental investigations showed that the length of pile has significant influence on resonant frequency and amplitude of the pile foundation. It has also been found that the slippage of pile from the surrounding soil considerably affects the resonance frequency and amplitude of the soil–pile foundation system.


      PubDate: 2016-04-19T17:26:06Z
       
  • Corrigendum to "Limit sliding-block seismic displacement for landslide
           triggering along slip surfaces consisting of saturated sand". Soil
           Dynamics and Earthquake Engineering 79 (2015) 265–277
    • Abstract: Publication date: Available online 7 April 2016
      Source:Soil Dynamics and Earthquake Engineering
      Author(s): Constantine A. Stamatopoulos



      PubDate: 2016-04-08T22:23:32Z
       
  • Rocking vibration of a rigid disc embedded in any depth of a coupled
           seawater-visco-poro-elastic seabed half-space
    • Abstract: Publication date: June 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 85
      Author(s): Rui He
      This paper models the rocking vibration of a rigid disc embedded in a visco-poro-elastic seabed, covered by a compressible inviscid seawater half-space. The behavior of water and soil are governed by Euler equations and the Biot׳s theory, respectively. The contact surface of the disc with the soil is smooth. The coupled rocking vibration problem is formulated using Helmholtz potentials combined with boundary conditions at the seawater–seabed interface and plane passing through the disc. With the help of integral transforms, the governing dual integral equations are changed to Fredholm integral equations of the second kind. The dynamic impedances for both permeable and impermeable discs are obtained with different embedded depths, soil conditions, and frequencies of excitation. It is found that when the embedded depth is larger than the diameter of the disc, increasing the embedment depth will not increase the rocking impedances any more.


      PubDate: 2016-04-08T22:23:32Z
       
  • Multi-step prediction of strong earthquake ground motions and seismic
           responses of SDOF systems based on EMD-ELM method
    • Abstract: Publication date: June 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 85
      Author(s): Dixiong Yang, Kaisheng Yang
      This paper proposes a new multi-step prediction method of EMD-ELM (empirical mode decomposition-extreme learning machine) to achieve the short-term prediction of strong earthquake ground motions. Firstly, the acceleration time histories of near-fault ground motions with nonstationary property are decomposed into several components of intrinsic mode functions (IMFs) with different characteristic scales by the technique of EMD. Subsequently, the ELM method is utilized to predict the IMF components. Moreover, the predicted values of each IMF component are superimposed, and the short-term prediction of ground motions is attained with low error. The predicted results of near-fault acceleration records demonstrate that the EMD-ELM method can realize multi-step prediction of acceleration records with relatively high accuracy. Finally, the elastic and inelastic acceleration, velocity and displacement responses of single degree of freedom (SDOF) systems are also predicted with satisfactory accuracy by EMD-ELM method.


      PubDate: 2016-04-08T22:23:32Z
       
  • Non-linear modeling of seismic isolation systems made of recycled
           tire-rubber
    • Abstract: Publication date: June 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 85
      Author(s): Santiago Brunet, Juan Carlos de la Llera, Eduardo Kausel
      This article considers the effectiveness of a seismic isolation system composed of a shallow layer of soil mixed with sand and rubber from shredded tires. A thorough review of past work is first provided, which is then followed by an evaluation of the constitutive properties of sand-rubber soil mixtures when these undergo large states of deformation and slip. Finally, a comprehensive set of simulations that involve a structure underlain by a strongly non-linear, seismic isolating layer when subjected to a variety of actual earthquakes scaled to various peak accelerations, are considered in detail. It is shown that the concept of using soil-rubber mixtures for the purposes of seismic isolation appears promising. A thickness for the rubber–soil mixture of just 2–3m is likely to be enough to achieve good levels of reductions in the seismic response of the structure. This suggests the desirability of following these analyses with large-scale experimental verifications, not only to fully validate the concept, but also to quantify and assess the numerical predictions with our simple even if non-linear mechanical models, and verify the large-strain constitutive properties of the soil mixtures inferred from laboratory analyses.


      PubDate: 2016-04-08T22:23:32Z
       
  • Geospatial modelling of shear-wave velocity and fundamental site period of
           Quaternary marine and glacial sediments in the Ottawa and St. Lawrence
           Valleys, Canada
    • Abstract: Publication date: June 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 85
      Author(s): Miroslav Nastev, Michel Parent, Martin Ross, Danielle Howlett, Nicolas Benoit
      The shear wave velocity of surficial sediments (V S) and the fundamental site period (T O) are important parameters for analysis of the free-field seismic response. Their spatial distribution in the Ottawa and St. Lawrence Valleys, Canada, was determined applying a standardized method consisting of (i) updating the Quaternary geology; (ii) classifying the surficial units with similar physical properties into three broad categories: upper sandy sediments, intermediate clayey sediments and basal glacial and non-glacial deposits; (iii) delineating the spatial thickness of each category by way of 3D geologic modelling; (iv) sorting of available geophysical data with respect to each individual category and assigning representative VS relationships: a power velocity-depth function for sand and clay units combined, V S=119+8.1 Depth0.5 (m/s), and a constant interval V S equal to the observed geometric mean velocity for glacial and non-glacial deposits, V S=385 (m/s). The respective T O values were computed as the ratio between the soil thickness and the average V S from ground surface to the bedrock. Validation of model results was conducted with V S and T O field data and available T O estimates from detailed urban-scale seismic zonation studies. The analyses of the uncertainty originating from the variation of the V S measurements showed that the standard deviations were roughly one-third of the modelled V S and T O values.


      PubDate: 2016-04-08T22:23:32Z
       
  • Mutual seismic assessment and isolation of different art objects
    • Abstract: Publication date: June 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 85
      Author(s): Stefano Sorace, Gloria Terenzi, Camilla Bitossi, Elena Mori
      New developments of a research programme dedicated to the seismic performance assessment and base isolation protection of art objects are presented in this paper. The investigation field has been extended from massive marble statues, considered at first step of this study, to slender free-standing columns, and bronze statues with highly vulnerable geometrical portions. A semicircular marble column and an equestrian bronze sculpture located in the main hall of the Restoration Laboratories of the Opificio delle Pietre Dure Institute in Florence are examined as representative case studies of the two classes, respectively. Rocking and sliding effects are simulated in the time-history assessment analyses of both artefacts, carried out by introducing all simultaneous components of seismic action as input. The results show an overturning-related near-collapse response of the column, and a plasticization-induced collapse of the statue, at the maximum considered earthquake level. In view of the different material and structural characteristics of the two artworks and several other art objects and equipments situated in the same hall, a mutual advanced seismic protection strategy is adopted, consisting in the base isolation of the floor by means of double curved surface sliders. This retrofit measure guarantees completely undamaged response conditions of the column and the statue, without requiring direct interventions on the two artworks. At the same time, the base-isolated floor constitutes a highly protective support for the hi-tech equipments housed in the Laboratories, as well as for any other artefact to be placed on it in the future.


      PubDate: 2016-04-08T22:23:32Z
       
  • Using elastic bridge bearings to reduce train-induced ground vibrations:
           An experimental and numerical study
    • Abstract: Publication date: June 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 85
      Author(s): Xiaozhen Li, Zhijun Zhang, Xun Zhang
      In order to investigate the influences of elastic bearings on ground vibrations induced by trains traversing a bridge, a numerical model was established based on the combination of train/track/bridge and pier/pile/soil subsystems. The elastic bearings in the train/track/bridge subsystem were simulated by a spring-dashpot element. The two subsystems were linked by the bearing reaction forces, and the whole model was calculated in the time domain. The numerically computed ground vibrations were compared with measured ones to validate the model. On this basis, the influences of elastic bearings on train, bridge and ground responses were discussed. Results show that the dynamic responses of the train are hardly affected, while the dynamic responses at the pier top and on the ground are clearly attenuated in the frequency band above 40Hz. Some increments in the frequency range 8–30Hz can be observed around the eigenfrequency of the main girder-elastic bearing system. The laws of bearing stiffness influences on ground vibrations were similar for different stiffnesses of the elastic bearings. Within a distance of 15m from the bridge, elastic bearings with stiffnesses of 2400, 2000 and 1600MN/m can reduce ground vibrations. However, at locations more than 22.5m from the bridge, ground vibrations may be close to or even a little larger than those of the rigid bearing case. When the elastic bearing has a stiffness of 1200MN/m, ground vibrations are clearly decreased at all locations.


      PubDate: 2016-03-31T09:30:02Z
       
  • A new analytical approach to reconstruct the acceleration time history at
           the bedrock base from the free surface signal records
    • Abstract: Publication date: June 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 85
      Author(s): V.R. Feldgun, Y.S. Karinski, D.Z. Yankelevsky, A.V. Kochetkov
      Acceleration time histories of earthquake events are typically measured in seismic stations that are placed close to the soil top surface. These acceleration records are often used as input data for seismic analysis. It may be used for base excitation in seismic analysis of above ground structures with shallow foundations.. However it may not be used for seismic analysis of underground structures, or even for above ground buildings with deep foundations and several underground stories. The required base excitation data of the latter should have been measured below the top surface, at a level that may be determined according to the specific analyzed building geometry or at the bedrock below. If the acceleration time history at the bedrock would have been known, the seismic wave propagation through the soil medium, from the bedrock towards the top surface, could have been carried out and the base excitation of the buried structure could be determined. Since there is no data on the acceleration time history at the bedrock, and the only given data is the acceleration records at the top surface, the goal of this paper is to provide an exact reverse analysis procedure to determine the unknown acceleration time history at the bedrock that would exactly produce the measured acceleration time history at the top surface. Once this goal is achieved, seismic analysis of buried structures may be carried out with the determined acceleration record at the bedrock as input. This paper presents an analytical exact solution of the inverse problem for determination of the acceleration, velocity and displacement time histories at the bedrock base of a layered geological medium that are compatible with the given acceleration record at the soil top surface. This new proposed method is based on analytical solutions of the initial-boundary value problems of the linear wave equation in the case of a layered medium. The relationship between waves in one layer and waves in another adjacent layer is derived considering the continuity of stresses and displacements at the common interface between the layers. The efficiency and accuracy of the proposed method is demonstrated through several examples involving the nonstationary response of the free surface. The case of the San Fernando Earthquake is studied. Excellent agreement is achieved between the recorded free surface time history and the reconstructed signal. This excellent agreement is obtained due to the exact analytical method used in deriving the inverse problem solution. This exact analytical method allows one to obtain an acceleration (velocity/displacement) distribution along all the layers at any time.


      PubDate: 2016-03-25T05:41:52Z
       
  • Seismic analysis of underground tunnels by the 2.5D finite/infinite
           element approach
    • Abstract: Publication date: June 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 85
      Author(s): K.C. Lin, H.H. Hung, Judy P. Yang, Y.B. Yang
      A procedure for the seismic analysis of underground tunnels using recorded free-field earthquakes based on the 2.5D finite/infinite element approach is presented. The near and far fields of the half space are modeled by finite and infinite elements, respectively. Using the 1D wave theory, the nodal force and displacement on the near-field boundary are computed for each spectral frequency of the earthquake. Then, equivalent seismic forces are computed for the near-field boundary for the earthquake spectrum. By assuming the soil-tunnel system to be uniform along the tunnel axis, the 2.5D approach can account for the wave transmission along the tunnel axis, which reduces to the 2D case for infinite transmission velocity. The horizontal and vertical components of the 1999 Chi-Chi Earthquake (TCU068) are adopted as the free-field motions in the numerical analysis. The maximal stresses and distribution patterns of the tunnel section under the P- and SV-waves are thoroughly studied by the 2.5D and 2D approaches, which should prove useful to the design of underground tunnels.


      PubDate: 2016-03-25T05:41:52Z
       
  • Seismic ground response at Lotung: Hysteretic elasto-plastic-based 3D
           analyses
    • Abstract: Publication date: June 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 85
      Author(s): A. Amorosi, D. Boldini, A. di Lernia
      This paper presents a non-linear finite element study to back-interpret the free field seismic response recorded at the Lotung Large-Scale Seismic Test site. The study is carried out in the time domain by the Finite Element (FE) code PLAXIS 3D, considering the vertical wave propagation of both the horizontal components of motion. The non-linear soil behaviour is simulated through a constitutive model, the Hardening Soil model with Small-Strain Stiffness (HSsmall), capable of describing the cyclic response of the material at different strain levels. In the paper, the constitutive response of the HSsmall model is firstly investigated through numerical simulations of strain-controlled cyclic shear tests under single and multi-directional conditions at low strain levels. Then, it is adopted to back-analyse the recorded free field seismic response, comparing the FE numerical results to the in-situ down-hole and surface signals recorded during two earthquakes occurred on May 20th and July 17th 1986, characterized by different peak ground accelerations.


      PubDate: 2016-03-25T05:41:52Z
       
  • On planar seismic wavefront modeling for estimating rotational ground
           motions: Case of 2-D SH line-source
    • Abstract: Publication date: June 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 85
      Author(s): Varun K. Singla, Vinay K. Gupta
      At large hypocentral distances, it is convenient to approximate the curved transient seismic wavefronts as planar to estimate rotational ground motions from the single-station recordings of translational ground motions. In this paper, we investigate whether and when this approximation, referred to as the ‘plane-wave’ approximation, can be considered adequate close to the source. For this, we consider a simplistic source model comprising a two-dimensional, kinematic shear dislocation SH line-source buried in a homogenous, elastic half-space and assume this to be an equivalent representation of a finite-sized fault. The ‘plane-wave’ rotational motion is then synthesized from the exact translational motion solution to the assumed model and compared with the exact rotational motion solution for this model. The comparison between the two sets of rotational amplitudes in frequency domain suggests that the plane-wave approximation may be adequate, when the wavelengths of the seismic waves are much smaller than the source depth. When this is not true, the plane-wave approximation is seen to underestimate the Fourier amplitudes close to the source by several orders, particularly when the fault planes are vertically oriented. A similar comparison in the time domain indicates that a severe underestimation may also occur when the source rise time is longer than the shear-wave arrival time at the epicenter. Significant discrepancies are also observed between the waveforms of the exact and plane-wave rotational motions.


      PubDate: 2016-03-25T05:41:52Z
       
  • Liquefaction potential analysis of the Kashmir valley alluvium, NW
           Himalaya
    • Abstract: Publication date: June 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 85
      Author(s): Hamid Sana, Sankar Kumar Nath
      We present the liquefaction potential analysis of Kashmir valley alluvium in general with special emphasis to four benchmark localities. The synthetic ground motions from the site response analysis of the valley during the 8 October 2005 Kashmir earthquake of Mw 7.6 are used as input motions. To determine the dynamic properties of soil, 64 SPT (Standard Penetration Test) boreholes spread across the valley were used. The analysis shows that the northwestern part of the Kashmir valley has very high, central part very high to high and southeastern part low to very low liquefaction potential, as measured on the Liquefaction Potential Index (LPI) scale. These results are complemented by the field investigations carried out after the earthquake wherein liquefaction features were observed in the northwestern part of the valley. At the benchmark sites, the soil profiles of Baramulla (Ahtishampora) and Kupwara are unsafe, showing a tendency to liquefy, while as in Anantnag (Khanabal) and Srinagar (Mehjoor Nagar) shallow layers are safe but the deeper layers are unsafe. As far as liquefaction potential is concerned, Baramulla (Ahtishampora) and Kupwara soil profiles show very high LPI values, Srinagar (Mehjoor Nagar) portrays high LPI, but Anantnag (Khanabal) exhibits low liquefaction potential.


      PubDate: 2016-03-25T05:41:52Z
       
  • Challenges associated with site response analyses for soft soils subjected
           to high-intensity input ground motions
    • Abstract: Publication date: June 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 85
      Author(s): Shawn C. Griffiths, Brady R. Cox, Ellen M. Rathje
      Nonlinear site response analyses are generally preferred over equivalent linear analyses for soft soil sites subjected to high-intensity input ground motions. However, both nonlinear (NL) and equivalent linear (EQL) analyses often result in large shear strain estimates (3–10%) at soft sites, and these large strains may generate unusual characteristics in the predicted surface ground motions, such as irregular time histories and atypical spectral shapes. One source of unusual ground motion predictions may be attributed to unrealistically low shear strengths implied by commonly used modulus reduction curves. Therefore, modulus reduction and damping curves can be modified at shear strains greater than approximately 0.1% to provide a more realistic soil model for site response. However, even after these modifications, nonlinear and equivalent linear site response analyses still may generate unusual surface acceleration time histories and Fourier amplitude spectra at soft soil sites when subjected to high-intensity input ground motions. In this study, we use equivalent linear and nonlinear 1D site response analyses for the well-known Treasure Island site to demonstrate challenges associated with accurately modeling large shear strains, and subsequent surface response, at soft soil sites.


      PubDate: 2016-03-21T09:09:31Z
       
  • Influences of stress magnitude and loading frequency on cyclic behavior of
           K0-consolidated marine clay involving principal stress rotation
    • Abstract: Publication date: May 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 84
      Author(s): Lin Guo, Jinmei Chen, Jun Wang, Yuanqiang Cai, Peng Deng
      Traffic load causes the change of magnitude and the rotation of principal stress and leads to a heart-shaped stress path in deviatoric stress space. To study the undrained behavior of natural clay under traffic load, a series of cyclic torsional shear tests were performed on Wenzhou marine clay. The specimens were first K 0-consolidated and then sheared and compressed under different cyclic stress magnitudes and loading frequencies. Experimental results show that both the stress magnitude and loading frequency have significant effects on accumulations of pore water pressure and strain development. Larger cyclic stress magnitude causes higher pore water pressure and larger vertical strain. The soft clay specimen reaches failure when the cyclic stress magnitude increases to a certain value. However, a decrease in loading frequency leads to an increase of pore water pore and vertical strain. When applied stress is small, hysteresis loop is almost closed. With the increase of the stress magnitude, the opening of hysteresis loop becomes clear, which means the increase of plastic strain. The higher the frequency is, the smaller the vertical elastic deformation is produced. Compared to cyclic stress magnitude, the impact of frequency on resilience behavior is not that significant.


      PubDate: 2016-03-06T09:03:26Z
       
  • Seismic hazard assessments for the Ordos Block and its periphery in China
    • Abstract: Publication date: May 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 84
      Author(s): Jingwei Liu, Furen Xie, Yuejun Lv
      Seismic hazards in the Ordos Block and its periphery were estimated based on 500 years of intensity observations. Firstly, historical intensity observations were collected, the completeness of the earthquake catalog was tested, and aftershocks were deleted. Secondly, the intensity data were digitized and placed in a geographic information system (GIS). Finally, the digitized intensity data were analyzed to determine the frequency–intensity relationship (i.e., seismic hazard curve) for each cell. The seismic hazards were quantified by the intensity and return period in a site or an area. Assuming a Poisson distribution for the earthquake occurrence in time, a probability of I≥VII, VIII, or IX in 50 years was quantified. We also estimated the corresponding intensities with 10% probability of exceedance in 50 years. The results show that the periphery of Ordos Block faces significant seismic hazards. Our study also suggests that the current designed peak ground acceleration or intensity for Ordos Block may not be adequate.


      PubDate: 2016-02-24T13:40:15Z
       
  • Efficacy of a sheet pile wall as a wave barrier for railway induced ground
           vibration
    • Abstract: Publication date: May 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 84
      Author(s): A. Dijckmans, A. Ekblad, A. Smekal, G. Degrande, G. Lombaert
      This paper investigates the effectiveness of a sheet pile wall to reduce railway induced vibration transmission by means of field measurements and numerical simulations. At Furet, Sweden, a sheet pile wall has been installed in the soil near the track to reduce train induced vibrations in houses close to the track. The depth of the sheet piles is 12 m with every fourth pile extended to 18 m . The efficacy of the wall is determined from in situ measurements of free field vibrations during train passages before and after installation of the sheet pile wall. The field test shows that the sheet pile wall reduces vibrations from 4 Hz upwards. Up till 16–20Hz, the performance generally increases with frequency and typically decreases with increasing distance behind the wall. The performance is further studied by means of two-and-a-half-dimensional coupled finite element–boundary element models. The sheet pile wall is modelled as an orthotropic plate using finite elements, while the soil is modelled as a layered halfspace using boundary elements. The sheet pile wall acts as a stiff wave barrier and the efficacy is determined by the depth and the stiffness contrast with soil. The reduction of vibration levels is entirely due to the relatively high axial stiffness and plate bending stiffness with respect to the horizontal axis of the sheet pile wall; the plate bending stiffness with respect to the vertical axis is too low to affect the transmission of vibrations. Therefore, it is important to take into account the orthotropic behaviour of the sheet pile wall. It is concluded that a sheet pile wall can effectively act as a wave barrier in soft soil conditions provided that the wall is sufficiently deep.


      PubDate: 2016-02-24T13:40:15Z
       
  • Editorial Board / Aims and Scope
    • Abstract: Publication date: April 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 83




      PubDate: 2016-02-24T13:40:15Z
       
  • Seismic stability analysis of slope reinforced with a row of piles
    • Abstract: Publication date: May 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 84
      Author(s): Ting-Kai Nian, Jing-Cai Jiang, Fa-Wu Wang, Qing Yang, Mao-Tian Luan
      In this paper, the seismic stability of a slope reinforced with a row of piles is analyzed within the framework of the pseudo-static approach. Calculations are conducted by using a technique integrated the kinematic theorem of limit analysis with strength reduction concept. The log-spiral failure surface is considered, analytical expressions are derived that enable one to readily calculate the yield acceleration coefficient for the slope subjected to seismic loading, and the lateral stabilizing force provided by piles which is required to increase the slope safety factor to a design value. Numerical results for typical example are presented and the reasonableness of the procedure is verified. Furthermore, discussions are made in order to illustrate the influence of horizontal seismic coefficients on the lateral stabilizing forces and the optimal position of the pile in seismic area.


      PubDate: 2016-02-24T13:40:15Z
       
  • Response of the Fatih Sultan Mehmet Suspension Bridge under spatially
           varying multi-point earthquake excitations
    • Abstract: Publication date: May 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 84
      Author(s): Nurdan Memisoglu Apaydin, Selcuk Bas, Ebru Harmandar
      The study aims at investigating the structural behavior of the Fatih Sultan Mehmet Suspension Bridge, i.e. the second Bosphorus Bridge in Turkey, under multi-point earthquake excitations, and determining the earthquake performance of the bridge based on the results obtained from this analysis. For this objective, spatially varying ground motions in triple direction were produced for each support of the bridge considering the Mw=7.4 scenario earthquakes on the main Marmara Fault. In order to simulate the ground motions, modified stochastic finite-fault technique was utilized. Taking the ground motions into account, non-linear time-history analysis was carried out, and the results obtained from the analysis were compared to those from uniform support earthquake excitation to identify the effects of multi-point earthquake excitations on the seismic performance of the bridge. From the analysis, it was determined that modal response of the towers and the deck was mostly effective on dynamic response of the entire bridge rather than other structural elements, such as cable and approach viaduct. Compared to the results obtained from simple-point earthquake excitation, noticeable axial force increase in the cable elements was obtained under multi-point earthquake excitation. The changes at the main cable and the side span cable were determined as 21% and 18%, respectively. This much increase in the cable elements led to increase in axial force at the towers and in shear force at the base section of the tower column. These changes in the structural elements were closely related to response of the deck and the towers since they had considerable contribution to response of the entire bridge. Based on the findings from the study, spatially varying ground motions has to be considered for long span suspension bridges, and the multi-support earthquake analysis should be carried out for better understanding and obtaining reliable results necessary for retrofitting and performance evaluation.


      PubDate: 2016-02-24T13:40:15Z
       
  • Theoretical basis and numerical simulation of parallel seismic test for
           existing piles using flexural wave
    • Abstract: Publication date: May 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 84
      Author(s): Jing-Yi Zhang, Long-Zhu Chen, Jinying Zhu
      This paper presents theoretical analysis of the parallel seismic (PS) method for evaluating existing piles using the flexural mode wave exited by a horizontal impact on the lateral surface of a pile. A simplified theoretical model of the flexural wave for PS method was established to elaborate the theoretical basis. A correction factor was then obtained and proposed to correct the pile depth obtained from the PS method, thus providing a more accurate estimation. A three dimension (3-D) finite element (FE) model was developed and the existence of the flexural waves on branch F(1, 1) in the pile shaft has been verified. Two time domain methods were used to calculate the flexural wave velocity in the pile. One was based on the pile tip reflection signal using a model where pile head reflection was minimized, and another method used the slope of the upper fitted line in the PS test. The flexural wave velocities from both methods match well with the predicted flexural wave group velocity determined from the dispersion curve of a 1-D rod embedded in the soil. The accuracy in estimation of pile tip depth is improved by applying the correction factor. A series of parametric studies were carried out to demonstrate the effectiveness of using flexural wave for PS test and the correction factor proposed in this study.


      PubDate: 2016-02-17T12:04:46Z
       
  • Static vulnerability of an existing r.c. structure and seismic
           retrofitting by CFRP and base-isolation: A case study
    • Abstract: Publication date: May 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 84
      Author(s): Fabio Mazza, Daniela Pucci
      The assessment of the static vulnerability under gravity loads of existing reinforced concrete (r.c.) framed buildings is a serious problem that requires the use of reliable methodologies to evaluate ductile and brittle mechanisms. The present work compares alternative formulations of member chord rotation and section and joint shear strength, proposed by Italian and European seismic codes and guidelines and other expressions available in the scientific literature. To this end, a r.c. framed building built sixty years ago with bi-directional (perimeter) and mono-directional (interior) plane frames, originally designed for five storeys then elevated to six during construction, is studied. A full characterization of the structure and its materials is carried out by means of destructive and non-destructive methods. Then, retrofitting based on the use of both innovative material, such as carbon fibre reinforced polymers (CFRP), and technology, such as base-isolation, are adopted to improve the static and seismic performances of the original structure. Finally, nonlinear analyses are carried out on a three-dimensional fibre model of the original and retrofitted structures, where an elastic linear law idealizes the behaviour of the CFRP up to tension failure and viscoelastic linear and bilinear models are used to idealize the behaviour of the elastomeric and sliding bearings, respectively.


      PubDate: 2016-02-17T12:04:46Z
       
  • Consideration of the rupture model uncertainties in the probabilistic
           seismic hazard analysis
    • Abstract: Publication date: April 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 83
      Author(s): Ali Farhadi, Mehdi Mousavi
      The uncertainties associated with the fault rupture model, i.e. down dip rupture width, subsurface rupture length and fault’s dip angle are not considered in the conventional probabilistic seismic hazard analyses (PSHA). The dip angle as an epistemic uncertainty is commonly assumed as a fixed value for a specific fault. Additionally, down dip rupture width and subsurface rupture length are determined from empirical relations. The main hypothesis of this paper was that the results of PSHA may be significantly influenced by considering the rupture model parameters as random variables instead of fixed values. The Monte Carlo simulation, as a powerful tool for uncertainty propagation analysis, was used for this objective. The NGA-West 2 database, as well as the Wells and Coppersmith (1994) [4] study was applied to describe the rupture model parameters in a stochastic manner. The results confirmed that hazard values derived from the Monte Carlo simulation method are significantly different from those derived from the classical approach. Depending on the attenuation relation and the style of faulting, theses differences leads to over/underestimation of hazard, especially at shorter periods in a characteristic band of region.


      PubDate: 2016-02-17T12:04:46Z
       
  • Factors influencing soil surface seismic hazard curves
    • Abstract: Publication date: April 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 83
      Author(s): Menzer Pehlivan, Ellen M. Rathje, Robert B. Gilbert
      Performance-based seismic design of important structures requires design ground motions from probabilistic seismic hazard analysis (PSHA) that incorporate the effects of local site conditions. Seismic hazard curves incorporating site-specific soil conditions can be generated through the convolution of rock hazard curves with statistical models for site-specific ground motion amplification factors ( AF ). The AF relationships are developed from a series of site response analyses. The goal of this study is to evaluate how the AF relationships and the resulting surface hazard curves are influenced by different approaches in the site response analysis, specifically the time series (TS) vs. random vibration theory (RVT) approaches, and by different levels of shear wave velocity variability introduced in the site response analysis. The results show that the median AF relationships derived from TS and RVT analyses are similar, except at periods near the site period, where RVT analysis may predict larger AF . Including the effect of shear wave velocity variability reduces the median AF and increases the standard deviation associated with the AF relationship ( σ ln AF ). Generally, the soil hazard curve derived by the AF relationship with the largest σ ln AF generates the largest ground motions, and this effect is most significant at small annual frequencies of exceedance. The effect of σ ln AF on soil hazard curves is larger than the effect of different median AF relationships. The value of σ ln AF is influenced significantly by the variability in the shear wave velocity and therefore proper specification of this variability is critical when developing soil hazard curves.


      PubDate: 2016-02-17T12:04:46Z
       
  • FEM-based parametric analysis of a typical gravity dam considering input
           excitation mechanism
    • Abstract: Publication date: May 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 84
      Author(s): M.A. Hariri-Ardebili, S.M. Seyed-Kolbadi, M.R. Kianoush
      This paper studies computer-aided parametric analysis on the finite element model of a typical concrete gravity dam. The coupled dam–foundation–reservoir system is modeled based on Lagrangian–Eulerian approach. The nonlinearity in the dam is originated from a developed rotating smeared crack model. Different types of input ground motions are used for excitation of the structural system, i.e. near-fault vs. far-field, real vs. artificial, and uniform vs. non-uniform. The spatial varying ground motions and endurance time acceleration functions are generated based on a non-stationary random process. Finally, results are presented in terms of displacement and crack propagation. Relative importance of different parameters is compared and an optimum numerical model is suggested for potential applications.


      PubDate: 2016-02-17T12:04:46Z
       
  • Cyclic resistance and liquefaction behavior of silt and sandy silt soils
    • Abstract: Publication date: April 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 83
      Author(s): Ali El Takch, Abouzar Sadrekarimi, Hesham El Naggar
      The liquefaction behavior and cyclic resistance ratio (CRR) of reconstituted samples of non-plastic silt and sandy silts with 50% and 75% silt content are examined using constant-volume cyclic and monotonic ring shear tests along with bender element shear wave velocity (V s) measurements. Liquefaction occurred at excess pore water pressure ratios (r u) between 0.6 and 0.7 associated with cumulative cyclic shear strains (γ) of 4% to 7%, after which cyclic liquefaction ensued with very large shear strains and excess pore water pressure ratio (r u>0.8). The cyclic ring shear tests demonstrate that cyclic resistance ratio of silt and sandy silts decreases with increasing void ratio, or with decreasing silt content at a certain void ratio. The results also show good agreement with those from cyclic direct simple shear tests on silts and sandy silts. A unique correlation is developed for estimating CRR of silts and sandy silts (with more than 50% silt content) from stress-normalized shear wave velocity measurements (V s1) with negligible effect of silt content. The results indicate that the existing CRR–V s1 correlations would underestimate the liquefaction resistance of silts and sandy silt soils.


      PubDate: 2016-02-12T11:57:08Z
       
  • Dynamic response of axisymmetric transversely isotropic viscoelastic
           continuously nonhomogeneous half-space
    • Abstract: Publication date: April 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 83
      Author(s): Saeed Cheshmehkani, Morteza Eskandari-Ghadi
      An analytical derivation is presented for dynamic response of axisymmetric transversely isotropic linear viscoelastic continuously nonhomogeneous half-space subjected to vertical either point or circular patch load. The material coefficients are considered to vary in terms of depth as bounded exponentially functions, and the mass density is assumed to be constant. Hankel integral transforms accompanied with Frobenius series method are applied to solve the boundary value problem. The unknown constants are determined by satisfying boundary conditions and regularity conditions at infinity, after which the displacement and stress fields are specified in Hankel space. The inverse Hankel integral transforms are utilized to specify the displacements and stresses in real domain. It is shown that inhomogeneity parameters affect the dynamic response of the half-space considerably, especially at the vicinity of the free-surface. Moreover, viscoelastic behavior of the half-space is parametrically studied assuming several damping ratios, and it is seen that it can considerably change the dynamic responses especially for long horizontal distances from the excitation point.


      PubDate: 2016-02-12T11:57:08Z
       
  • Influence of fines content on the undrained cyclic shear strength of
           sand–clay mixtures
    • Abstract: Publication date: April 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 83
      Author(s): Ukgie Kim, Dongwook Kim, Li Zhuang
      A series of undrained cyclic triaxial tests were performed on sand–clay mixtures with various sand–clay mixing ratios. Prior to the primary tests, the threshold fines content was examined by consistency tests, which was found to be approximately 20%. For sand–clay mixtures with a sand-matrix (fines content less than the threshold fines content), the cyclic shear strength of low-density mixtures increases and that of high-density mixtures decreases with increasing fines content. However, for sand–clay mixtures with a fines-matrix (fines content greater than the threshold fines content), there exists a unique correlation between the cyclic shear strength and global void ratio for different fines content. The equivalent granular void ratio is introduced in this paper to account for the contribution ratio of the fines to soil skeleton. As a result, a unique relationship between cyclic shear strength and equivalent granular void ratio was observed for pure sand and sand–clay mixtures with a sand-matrix.


      PubDate: 2016-02-12T11:57:08Z
       
  • An analytical method for evaluating highway embankment responses with
           consideration of dynamic wheel–pavement interactions
    • Abstract: Publication date: April 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 83
      Author(s): Zheng Lu, Zhi Hu, Hailin Yao, Jie Liu, Yongxiang Zhan
      In this paper, a more realistic vehicle-road-ground coupling model is proposed to evaluate the dynamic responses of highway embankment with consideration of dynamic wheel–pavement interactions. The vehicle is modelled as a multi-degrees-of-freedom (MDOF) system, and the pavement and embankment are treated as two elastic layers resting on a poroelastic half-space soil medium. The dynamic wheel–pavement force is considered by introducing a Hertzian contact spring between the wheel and the pavement. The vehicles and the road-ground subsystem are coupled by displacement compatibility at the wheel–pavement contact area. The dynamic stiffness matrix method is developed to address the road-ground system, and priority is given to a simple formulation based on the principle of spatial Fourier transforms that are compatible with good numerical efficiency and provide quick solutions. Using a FFT (Fast Fourier Transform) algorithm, the numerical results are derived by introducing two typical vehicles. The results show that two peaks of the vertical responses can be observed with increases in the vehicle speed and the wavelength of the pavement unevenness because of resonance in the coupling system. The dynamic wheel–pavement force makes an important contribution to the responses of the embankment, and the influences of the pavement unevenness parameters and pavement rigidity on the dynamic response of the embankment are also significant.


      PubDate: 2016-02-12T11:57:08Z
       
  • Structural health assessment and restoration procedure of an old riveted
           steel arch bridge
    • Abstract: Publication date: April 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 83
      Author(s): Alemdar Bayraktar, Ahmet Can Altunişik, Temel Türker
      Structural health assessment of the old bridges is very important because of the fact that some bridges have been damaged or destroyed in the world every year. The paper presents the structural health monitoring, safety identification and restoration proposals for an old riveted arch steel bridge. The selected bridge is named as Borçka Steel Arch Bridge and it is located in Artvin, Turkey. Firstly, in-situ structural investigations on the bridge are presented. Then ambient vibration test are carried out on the Bridge in order to determine the experimental dynamic characteristics called as the natural frequencies, mode shapes and modal damping ratios. The measurement is performed under the environmental effects of pedestrian movement and wind-induced vibration by using uniaxial seismic accelerometers. The accelerometers are placed to the bridge deck in both the vertical and horizontal directions. The initial finite element model developed according to the building survey data is updated by using the dynamic test results. The updated finite element model is analyzed for the different load cases including dead, moving, wind and earthquake loads. Restoration recommendations are made according to the results from site investigations and analysis. The existing and restorated models of the bridge are checked to the design criteria in AISC-ASD 89 (1989).


      PubDate: 2016-02-12T11:57:08Z
       
  • A preliminary empirical model for frequency-dependent attenuation of
           Fourier amplitude spectra In Serbia from the Vrancea earthquakes
    • Abstract: Publication date: April 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 83
      Author(s): V.W. Lee, M.D. Trifunac, B. Bulajić, M. Manić
      We present the frequency-dependent attenuation model for Fourier amplitude spectra of strong earthquake ground motion in Serbia from intermediate depth earthquakes in the Vrancea source zone in Romania. The development of this type of scaling is the essential first step toward developing the corresponding attenuation and scaling equations for pseudo relative velocity spectra (PSV), which are necessary for seismic macro- and microzoning in the territory of Serbia. Such scaling is necessary because the Vrancea source zone produces large earthquakes with shaking that attenuates differently from the local earthquakes in Serbia. Development of such a scaling model is associated with several difficulties, the principal one being the lack of recorded strong motion accelerograms at epicentral distances exceeding 300km. To reduce uncertainties with such scaling, we require our preliminary scaling equations to be consistent with independent estimates of seismic moment, stress drop, and radiated wave energy. In the future, when the recorded strong motion data from Vrancea earthquakes increases several-fold of what it is today, it will become possible to perform this analysis again, thus leading to more reliable and permanent scaling estimates.


      PubDate: 2016-02-12T11:57:08Z
       
  • Dynamic analysis of a transversely isotropic multilayered half-plane
           subjected to a moving load
    • Abstract: Publication date: April 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 83
      Author(s): Zhi Yong Ai, Guang Peng Ren
      In this paper, the analytical layer-element method is utilized to analyze the plane strain dynamic response of a transversely isotropic multilayered half-plane due to a moving load. We assume that the studied system moves synchronously with the moving load, then the moving load relative to the moving system is considered to be motionless. Therefore, the vertical stress and the vertical displacement under the moving load need not update for the variation of the load position. Based on the governing equations of motion in the moving system, the analytical layer-element solutions for a finite layer and a half-plane in the Fourier transform domain are derived by using the algebraic operations in Ref. [7]. The global matrix of the problem can be obtained by assembling the analytical layer-elements of all layers. The corresponding solution in the frequency domain is further recovered by the inverse Fourier transform. Several examples are given to confirm the accuracy of the proposed method and to illustrate the influence of material properties.


      PubDate: 2016-02-12T11:57:08Z
       
  • Vibration control by damped braces of fire-damaged steel structures
           subjected to wind and seismic loads
    • Abstract: Publication date: April 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 83
      Author(s): Fabio Mazza, Marco Fiore
      The aim of the present work is to evaluate the effectiveness of viscoelastic-damped braces (VEDBs) to improve the wind and earthquake responses of fire-damaged steel framed buildings, where a significant reduction of stiffness and strength properties of the structural elements following exposure to fire is highlighted. To this end, a ten-storey steel office building, designed for a low-risk zone under the former Italian seismic code and in line with Eurocodes 1 and 3, is considered as test structure. The dynamic response of the test structure in a no fire situation is compared with what would happen in the event of three fire scenarios, on the assumption that the fire compartment with a uniform temperature is confined to the area of the first (i.e. F1), fifth (i.e. F5) and tenth (i.e. F10) level, with the parametric temperature–time fire curve evaluated in line with Eurocode 1. Two retrofitting structural solutions are examined to upgrade the fire damaged test structures, by inserting diagonal steel braces with or without viscoelastic dampers. Frame members are idealized by a bilinear model, which allows the simulation of the nonlinear behavior under seismic loads, while an elastic linear law is considered for diagonal braces. Finally, viscoelastic dampers are idealized by means of a frequency-dependent model.


      PubDate: 2016-02-01T11:44:47Z
       
  • Seismic ground motion amplification pattern induced by a subway tunnel:
           Shaking table testing and numerical simulation
    • Abstract: Publication date: April 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 83
      Author(s): Masoud Rabeti Moghadam, Mohammad Hassan Baziar
      A series of 1g shaking table tests, followed by the numerical simulations, is performed to investigate the effect of a circular subway tunnel on the ground motion amplification pattern. Effects of various parameters, including shear wave velocity of soil, frequency content of input motion, flexibility ratio and tunnel depth on the amplification pattern is investigated. Experimental study revealed that the tunnel did not affect free field response at dimensionless period greater than 10. Subsequent parametric study demonstrated that the amount of amplifications were mainly controlled by dimensionless period, dimensionless depth and flexibility ratio. Tunnel effect on the amplification pattern is more prominent for dimensionless period between 3 to 10, flexibility ratio greater than 1 and dimensionless depth less than 3. The study revealed that subway tunnel influences the seismic response of low period buildings, constructed above the tunnel.


      PubDate: 2016-02-01T11:44:47Z
       
  • Investigation on the accuracy of the N2 method and the equivalent
           linearization procedure for different hysteretic models
    • Abstract: Publication date: April 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 83
      Author(s): Claudio Amadio, Giovanni Rinaldin, Massimo Fragiacomo
      In this paper, an extensive parametric study was carried out to evaluate the dynamic response of single degree of freedom (SDOF) systems with elasto-plastic and flag-shape hysteretic behaviour for three different dissipation capacities. Three sets of natural accelerograms were used, each one composed by at least 7 records which are on average spectrum-consistent in pseudo-acceleration, spectral displacement or both of them. All sets were also employed to draw the inelastic spectra for different ductility values. Such rigorous spectra were then compared with the approximated curves calculated using the N2 method and the Equivalent Linearization Procedure (ELP) based on the use of overdamped elastic spectra. The analyses demonstrate a general accuracy of the N2 method, which is mostly based on the ductility of the system, even for the hysteretic behaviour characterised by reduced energy dissipation. Larger discrepancies were found for systems with lower damping ratios and reduced fundamental periods. The ELP, which mainly depends upon the dissipated energy, led instead to overall slightly larger discrepancies than the N2 method, particularly for not dissipative and ductile systems, whereas the approximation is generally acceptable for elasto-plastic systems.


      PubDate: 2016-02-01T11:44:47Z
       
  • Identification of dynamic soil properties through shaking table tests on a
           large saturated sand specimen in a laminar shear box
    • Abstract: Publication date: April 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 83
      Author(s): Chi-Chin Tsai, Wei-Chun Lin, Jiunn-Shyang Chiou
      Many laminar shear boxes have recently been developed into sliding-frame containers that can reproduce 1D ground-response boundary conditions. The measured responses of such large specimens can be utilized to back-calculate soil properties. This study investigates how the boundary effect in large specimens affects the identified soil properties through shaking table tests on a soil-filled large laminar box conducted at the National Center for Research on Earthquake Engineering in Taiwan. The tested soil-box system is unique because only 80% of the container is filled with soil. This system can be regarded as a two-layer system: an empty top and soil-filled bottom. The dynamic properties of this two-layer system are identified through various approaches, including theoretical solutions of wave propagation, free vibration, and nonparametric stress–strain analyzes. Therefore, the coupling effect of the box and soil can be evaluated. Results show that, compared with the two-layer system considering the influence of the box, the conventional approach with a single-layer system slightly underestimates shear wave velocity but obtains the same damping ratio of the soil layer. In addition, the identified modulus reduction and damping curves in the two-layer system are consistent with those obtained in a laboratory test on a small specimen. Furthermore, based on detailed acceleration measurements along different depths of soil, a piecewise profile of shear wave velocity is built. The identified shear wave velocity increases with depth, which is not uniform and differs from the constant velocity typically assumed for the specimen.


      PubDate: 2016-02-01T11:44:47Z
       
  • Earth pressure of layered soil on retaining structures
    • Abstract: Publication date: April 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 83
      Author(s): Shi Han, Jinxing Gong, Yanqing Zhang
      Earth pressure evaluation of retaining structure is not a new thing in geotechnical engineering. Up to date, many analytical and numerical approaches have been developed, but limitations of these available approaches are obvious for the application in some situations. The main objective of this paper is to develop a method to predict the earthquake pressure of retaining structures based on wedge method with as few limitations as possible. The developed method is suitable for retaining structures in the case of layered backfill with zero slope angle from horizontal level and with curved failure surface. To generate a curved failure surface, the sliding wedge is divided into many thin-layer micro-elements and the equilibrium equations of each micro-element are established. In the case of seismic analysis, the seismic actions are considered as static inertia forces on layered micro-elements. The shape of failure surface is determined by using available optimization method. Effects of the friction angle between wall and backfill soil on the distribution of earth pressure and the shape of failure surface were investigated, and earth pressures estimated based on curved and linear failure surfaces were compared. Analysis results indicate that the potential failure surface in the backfill soil depends on the friction angle between wall and backfill soil. For small friction angle, the failure surface tends to be planar. The active earth pressures corresponding to curved and planar failure surfaces are almost identical, but the discrepancies between the results of the two failure surface are large and increase with the increase of wall friction. Comparisons between results of the proposed method and those of the available methods as well as experimental results were conducted. Comparison result indicates that the merits of the proposed method are obvious.


      PubDate: 2016-01-28T08:15:42Z
       
  • Closed form solution of Eigen frequency of monopile supported offshore
           wind turbines in deeper waters incorporating stiffness of substructure and
           SSI
    • Abstract: Publication date: April 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 83
      Author(s): Laszlo Arany, S. Bhattacharya, John H.G. Macdonald, S. John Hogan
      Offshore wind turbines (OWTs) are dynamically loaded structures and therefore the estimation of the natural frequency is an important design calculation to avoid resonance and resonance related effects (such as fatigue). Monopiles are currently the most used foundation type and are also being considered in deeper waters (>30m) where a stiff transition piece will join the monopile and the tapered tall tower. While rather computationally expensive, high fidelity finite element analysis can be carried to find the Eigen solutions of the whole system considering soil–structure interaction; a quick hand calculation method is often convenient during the design optimisation stage or conceptual design stage. This paper proposes a simplified methodology to obtain the first natural frequency of the whole system using only limited data on the WTG (Wind Turbine Generator), tower dimensions, monopile dimensions and the ground. The most uncertain component is the ground and is characterised by two parameters: type of ground profile (i.e. soil stiffness variation with depth) and the soil stiffness at one monopile depth below mudline. In this framework, the fixed base natural frequency of the wind turbine is first calculated and is then multiplied by two non-dimensional factors to account for the foundation flexibility (i.e. the effect of soil–structure interaction). The theoretical background behind the model is the Euler–Bernoulli and Timoshenko beam theories where the foundation is idealised by three coupled springs (lateral, rocking and cross-coupling). 10 wind turbines founded in different ground conditions from 10 different wind farms in Europe (e.g. Walney, Gunfleet sand, Burbo Bank, Belwind, Barrow, Kentish flat, Blyth, Lely, Thanet Sand, Irene Vorrink) have been analysed and the results compared with the measured natural frequencies. The results show good accuracy (errors below 3.5%). A step by step sample calculation is also shown for practical use of the proposed methodology.


      PubDate: 2016-01-22T08:06:46Z
       
  • Evaluation of underground tunnel response to reverse fault rupture using
           numerical approach
    • Abstract: Publication date: April 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 83
      Author(s): Mohammad Hassan Baziar, Ali Nabizadeh, Ronak Mehrabi, Chung Jung Lee, Wen Yi Hung
      The present paper implemented a finite-element methodology to simulate the interaction behavior between tunnel and sandy soil deposit when a reverse fault rupture propagated from the base rock to the ground surface. The location of shear zones and propagation of subsurface rupture traces through overlying sand were discussed with the changes in the tunnel location, tunnel rigidity and soil relative density. The results indicated that the presence of a tunnel could have a significant influence on the fault rupture path. It was further shown that different factors affected the rotation and displacement of the tunnel. This study also investigated the evolution of a surface deformation profile using both centrifuge experiments and the finite element simulation. The results of finite element studies were verified using centrifuge experiments. Reasonable agreement between numerical and experimental results indicated the credibility of the numerical approach. Verified numerical methodology was then used to present a parametric study, offering further insight into the effect of different parameters on the soil-tunnel interaction phenomenon.


      PubDate: 2016-01-22T08:06:46Z
       
 
 
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