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EARTH SCIENCES (471 journals)

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Journal Cover Soil Dynamics and Earthquake Engineering
  [SJR: 1.516]   [H-I: 56]   [14 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0267-7261
   Published by Elsevier Homepage  [3031 journals]
  • Full waveform tomography to resolve desert alluvium
    • Authors: Khiem T. Tran; Barbara Luke
      Pages: 1 - 8
      Abstract: Publication date: August 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 99
      Author(s): Khiem T. Tran, Barbara Luke
      This paper presents shear wave velocity distribution developed from full waveform tomography on a seismic dataset recorded in the northwest Las Vegas Valley, Nevada. The setting is a deep and variable alluvial sequence, encompassing gravel, sand, silt and clay, with some carbonate cementation. Seismic data were collected along a ~144-m long array using 72 equally spaced geophones, with an accelerated drop-weight source applied at 6-m intervals. The dataset was interpreted using an advanced 2-D full waveform tomography method. The same dataset was also analyzed using Rayleigh wave dispersion, following the multichannel analysis of surface waves (MASW) method, to develop a single, 1-D velocity profile. Results from the MASW method indicated a mild velocity inversion. The waveform tomography method was able to characterize vertical and lateral velocity variations along the array length to 25m depth. Results showed significantly contrasting high- and low-velocity layers. While depth-averaged shear wave velocities from the two methods were similar, the degree of variability indicated using FWI is supported by strong variation in Standard Penetration Test (SPT) blow counts from a nearby drillhole and by expectations from sediment lithology.

      PubDate: 2017-05-13T15:31:41Z
      DOI: 10.1016/j.soildyn.2017.04.018
      Issue No: Vol. 99 (2017)
       
  • Seismic response of concrete-rockfill combination dam using large-scale
           shaking table tests
    • Authors: Jianxin Wang; Gui Yang; Hanlong Liu; Sanjay Shrawan Nimbalkar; Xinjun Tang; Yang Xiao
      Pages: 9 - 19
      Abstract: Publication date: August 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 99
      Author(s): Jianxin Wang, Gui Yang, Hanlong Liu, Sanjay Shrawan Nimbalkar, Xinjun Tang, Yang Xiao
      Concrete-rockfill combination dam (CRCD), a new type of dam, is mainly composed of an upstream concrete wall and a downstream inclined rockfill body. It is not in direct contact with the bedrock foundation but a water stop, which is different from conventional concrete gravity dam. The dynamic characteristics of CRCD are not quite fully understood yet. In this paper, large-scale models of CRCD were constructed and key parameters, such as acceleration-time response, dynamic earth pressure, deformation and failure pattern of slope were monitored. Results showed that the amplification factors in the upper part (0.6H) increased with the height. The model dam showed obvious concentration and amplification effect on the low frequency component. The total earth pressure acting on the back face of the wall varied approximately nonlinear along the wall height when the PGA exceeded 0.4g. In addition, the CRCD model exhibited good seismic performance with small residual deformation under earthquake. A shallow sliding mode of failure at a height of 0.8H was measured from the base on the downstream slope. Therefore, it was prudent to undertake some aseismatic reinforcement measurements at the top 1/5 thickness zone of the slope. These model test results could provide a certain reference value for preliminary understanding and qualitative analysis of a prototype CRCD.

      PubDate: 2017-05-13T15:31:41Z
      DOI: 10.1016/j.soildyn.2017.04.015
      Issue No: Vol. 99 (2017)
       
  • Seismic hazard analysis using simulated ground-motion time histories: The
           case of the Sefidrud dam, Iran
    • Authors: H. VahidiFard; H. Zafarani; S.R. Sabbagh-Yazdi; M.A. Hadian
      Pages: 20 - 34
      Abstract: Publication date: August 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 99
      Author(s): H. VahidiFard, H. Zafarani, S.R. Sabbagh-Yazdi, M.A. Hadian
      This study aims at conducting probabilistic seismic hazard analysis for the Sefidrud dam located near Rudbar City. For this purpose, firstly, the characteristic earthquake recurrence model for major earthquakes on individual main faults have been combined with the smaller (smoothed) background seismicity of the region. Then, appropriate ground motion prediction equations were applied to estimate hazard values. Finally, in order to obtain reliable estimation of seismic hazard due to sources close to the dam site and to investigate near-field characteristics of motion, the Rudbar fault as the most prominent earthquake source in the immediate vicinity of the site is considered in seismic hazard computation using hybrid broadband simulation based ground motion parameters. The results of this method with different declustering schemes are reported for two level of seismic hazard analysis (i.e. return periods of 475 and 2475 years). Best estimate seismic hazard maps of PGA and PGV values obtained from the logic tree method is presented. By inclusion of simulation results for the Rudbar fault in the probabilistic seismic hazard analysis (PSHA), maximum PGA and PGV for 475 years return period obtained around 340cm/s/s and 25cm/s, respectively. For classic PSHA without including simulation the maximum PGA and PGV for 475 years return period obtained around 450cm/s/s and 32cm/s, respectively. With the simulation-based PSHA for a 2475 years return period a maximum PGA of 650cm/s/s and PGV of 50cm/s have been estimated. Classic PSHA (without simulation) for a 2475 years return period has resulted a maximum PGA of 850cm/s/s and PGV of 65cm/s.

      PubDate: 2017-05-13T15:31:41Z
      DOI: 10.1016/j.soildyn.2017.04.017
      Issue No: Vol. 99 (2017)
       
  • Dynamic torsional response of an elastic pile in a radially inhomogeneous
           soil
    • Authors: Zhiqing Zhang; Ernian Pan
      Pages: 35 - 43
      Abstract: Publication date: August 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 99
      Author(s): Zhiqing Zhang, Ernian Pan
      Surrounding soil may be weakened or strengthened due to construction disturbance of the pile, resulting in soil properties varying gradually in the radial direction. In this paper, an analytical solution is developed to investigate the torsional vibration of an elastic pile embedded in a radially inhomogeneous soil and subjected to a time-harmonic torsional loading. The radially inhomogeneous soil is subdivided into many thin concentric annular sub-zones, with each having constant complex shear modulus in radial direction. The dynamic equilibrium equation of each sub-zone of the soil is then solved and the circumferential displacement and shear stress along the pile-soil interface are obtained by a newly developed method that enforces the continuity conditions between the two adjacent sub-zones. By virtue of the boundary and continuity conditions of the pile-soil system, the torsional impedance at the pile head is derived in an exact closed form in the frequency domain. Some numerical results are presented to study the influence of the soil layer rigidities on the vibration characteristic of the pile-soil system.

      PubDate: 2017-05-13T15:31:41Z
      DOI: 10.1016/j.soildyn.2017.04.020
      Issue No: Vol. 99 (2017)
       
  • Reciprocal absorbing boundary condition with perfectly matched discrete
           layers for the time-domain propagation of SH waves in a layered half-space
           
    • Authors: Cuong T. Nguyen; John L. Tassoulas
      Pages: 44 - 55
      Abstract: Publication date: August 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 99
      Author(s): Cuong T. Nguyen, John L. Tassoulas
      In this paper, a reciprocal absorbing boundary condition (RABC) is combined with perfectly matched discrete layers (PMDLs) for the time-domain numerical analysis of SH-wave propagation in a layered half-space. The RABC is employed for representation of the layered stratum beyond the vertical consistent transmitting boundary while the PMDLs are applied in order to absorb waves into the underlying homogeneous half-space. The combination of RABC and PMDLs circumvents concerns with the treatment of layered media. The RABC handles layers without any approximation, other than discretization, while PMDLs are used exclusively for the simulation of the homogeneous medium underlying the layers. This combination leads to solution of the problem of anti-plane shear wave-propagation in a layered half-space directly in the time domain. Examples are presented demonstrating the accuracy and effectiveness of the proposed combination.

      PubDate: 2017-05-13T15:31:41Z
      DOI: 10.1016/j.soildyn.2017.04.012
      Issue No: Vol. 99 (2017)
       
  • Wavelet-based simulation of scenario-specific nonstationary accelerograms
           and their GMPE compatibility
    • Authors: V.L. Nithin; S. Das; H.B. Kaushik
      Pages: 56 - 67
      Abstract: Publication date: August 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 99
      Author(s): V.L. Nithin, S. Das, H.B. Kaushik
      In seismic hazard analysis ground motion prediction equation (GMPE) plays a pivotal role because it provides the statistical distribution of hazard parameter for a chosen seismic scenario. However, GMPEs in general do not provide nonlinear response statistics, and the latter should be ideally obtained by time-history analyses of a scenario-specific suite of motions. In the present study a new wavelet-based method is proposed to simulate scenario-specific ensemble of accelerograms with realistic variability of time-frequency characteristics. Firstly, a methodology is proposed to stochastically characterize the nonstationarity of a recording process from the energy arrival curve of the wavelet coefficients of the recorded ground motion. Then a new empirical scaling model is developed to estimate the instantaneous energy arrival, with model uncertainty. Further, a reconstruction method is formulated to simulate the scenario-specific ensemble of accelerograms from the estimated scenario-specific energy arrival curves. It is found that the simulated ensemble exhibits realistic variation of time-frequency characteristics and hence, it naturally becomes comparable with GMPEs (in terms of median estimates for response spectrum and strong motion duration) developed using the same database. Finally, an algorithm is proposed to tune the estimated energy arrival such that the ensemble of simulated motions can be made compatible with the target GMPEs, both in terms of median estimates and standard deviations. It is found that the GMPE-compatible ensemble, obtained for 5% damping PSV spectra, shows good agreement with respect to PSV scaling models developed for a wide range of damping ratio.

      PubDate: 2017-05-13T15:31:41Z
      DOI: 10.1016/j.soildyn.2017.05.007
      Issue No: Vol. 99 (2017)
       
  • An alternative method for estimating Vs(30) from a shallow shear-wave
           velocity profile (depth <30m)
    • Authors: Su-Yang Wang; Hai-Yun Wang; Qiang Li
      Pages: 68 - 73
      Abstract: Publication date: August 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 99
      Author(s): Su-Yang Wang, Hai-Yun Wang, Qiang Li
      The near-surface travel-time averaged shear-wave velocity to 30m (Vs(30)) is a key parameter for ground-motion prediction equations and building codes. In many cases, however, shear-wave velocity profiles do not extend to 30m. In this article, we propose an alternative method for estimating Vs(30) from a shallow shear-wave velocity profile, using the travel-time averaged shear-wave velocities at two different depths (Vs(z 1 ) and Vs(z 2 ), and z 1 < z 2 <30m). Using the data from 643 boreholes from the KiK-net in Japan and 135 boreholes from California where the shear-wave velocity profile reaches at least 30m, the reliability of the proposed method is validated by the correlations between the measured and the estimated Vs(30) and the accuracy of site classification using the estimated Vs(30). The results show that the proposed method can estimate Vs(30) with high accuracy, as the Pearson correlation coefficients between the measured and the estimated Vs(30) are greater than 0.99, and the site classification successful rates using the estimated Vs(30) are greater than 94%, whereas z 1 ≥10m and z 2 ≥20m. Compared with the method of Wang and Wang (2015), the proposed method has a certain improvement in the accuracy, with higher correlations and accuracy of site classification.

      PubDate: 2017-05-13T15:31:41Z
      DOI: 10.1016/j.soildyn.2017.05.002
      Issue No: Vol. 99 (2017)
       
  • Seismic displacement along a log-spiral failure surface with crack using
           rock Hoek–Brown failure criterion
    • Authors: Lian-heng Zhao; Xiao Cheng; Liang Li; Jia-qi Chen; Yingbin Zhang
      Pages: 74 - 85
      Abstract: Publication date: August 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 99
      Author(s): Lian-heng Zhao, Xiao Cheng, Liang Li, Jia-qi Chen, Yingbin Zhang
      Earthquakes can trigger slope instability, especially in the case of slopes with cracks. The most commonly used method for analyzing seismic slope stability is the pseudo-static analysis technique. However, information about slope displacements is difficult to obtain. The purpose of this paper is to present a model for calculating the seismic displacements of rock slopes with cracks using the upper bound limit analysis and the rigid block displacement technique. The Hoek–Brown (H–B) failure criterion is employed in this model, and actual horizontal and vertical earthquake ground motion records are utilized. The equivalent Mohr–Coulomb (M–C) parameters including friction angle and cohesive strength are determined by fitting an average linear relationship to the curve of relationship between major and minor principle stresses for H–B failure criterion. A comparison of the seismic displacements obtained by using the equivalent M–C parameters and the H–B failure criterion is performed. The difference of the seismic displacements obtained by using the two methods is significantly larger than the difference of factor of safety for rock slopes with cracks under seismic action. The results indicate that the equivalent M–C parameters method may cause an overestimation of the stability of a slope. To understand the influence of rock strength parameters and crack depth, a detailed parametric study is carried out. These parameters can significantly influence seismic displacement, especially for large crack depths. For the numerical example considered in this study, the ratio of crack depth to slope height varied from 0 to 0.2, and the increase in seismic displacement can exceed 23%.

      PubDate: 2017-05-17T15:38:20Z
      DOI: 10.1016/j.soildyn.2017.04.019
      Issue No: Vol. 99 (2017)
       
  • Assessment of earthquake damage considering the characteristics of past
           events in South America
    • Authors: Mabé Villar-Vega; Vitor Silva
      Pages: 86 - 96
      Abstract: Publication date: August 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 99
      Author(s): Mabé Villar-Vega, Vitor Silva
      The evaluation of earthquake damage considering past events can be a useful tool to verify or calibrate damage and risk models, as well as to assess the possible consequences that future events may cause in a region. This study describes a process to estimate earthquake damage considering past events, and using the OpenQuake-engine, the open-source software for seismic hazard and risk analysis of the Global Earthquake Model Foundation. Exposure and fragility models from the recently completed South America Risk Assessment (SARA) project were combined with conditioned ground motion fields from past events to calculate structural damage in the affected region. These results can facilitate the creation of risk reduction measures, such as retrofitting campaigns, development of insurance mechanisms and enhancement of building codes. The challenges in assessing damage and losses from past events are thoroughly discussed, and several recommendations are proposed.

      PubDate: 2017-05-17T15:38:20Z
      DOI: 10.1016/j.soildyn.2017.05.004
      Issue No: Vol. 99 (2017)
       
  • A new ground motion intensity measure IB
    • Authors: Edén Bojórquez; Robespierre Chávez; Alfredo Reyes-Salazar; Sonia E. Ruiz; Juan Bojórquez
      Pages: 97 - 107
      Abstract: Publication date: August 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 99
      Author(s): Edén Bojórquez, Robespierre Chávez, Alfredo Reyes-Salazar, Sonia E. Ruiz, Juan Bojórquez
      In this study, a new generalized ground motion intensity measure is proposed. The new intensity measure named I B is able to increase the efficiency in the prediction of nonlinear behavior and higher modes effects of structures subjected to earthquake ground motions with different characteristics. The intensity measure is based on a recently proposed proxy of the spectral shape named N p , which has been successfully used in ground motion record selection for nonlinear dynamic analysis. Although the N p parameter was proposed by using the spectral shape in term of pseudo-acceleration, it will be observed that N p can be defined through other types of spectral shapes such as those obtained with velocity, displacement, input energy, inelastic parameters and so on. In addition, it is illustrated that several ground motion intensity measures are particular cases of the new generalized ground motion intensity measure here proposed, which is able to predict both nonlinear structural demands and higher modes effects on buildings under earthquake ground motions.

      PubDate: 2017-05-17T15:38:20Z
      DOI: 10.1016/j.soildyn.2017.05.011
      Issue No: Vol. 99 (2017)
       
  • Numerical modelling of micro-seismic and infrasound noise radiated by a
           wind turbine
    • Authors: Theodore V. Gortsas; Theodoros Triantafyllidis; Stylianos Chrisopoulos; Demosthenes Polyzos
      Pages: 108 - 123
      Abstract: Publication date: August 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 99
      Author(s): Theodore V. Gortsas, Theodoros Triantafyllidis, Stylianos Chrisopoulos, Demosthenes Polyzos
      Infrasound, low frequency noise and soil vibrations produced by large wind turbines might disturb the comfort of nearby structures and residents. In addition repowering close to urban areas produces some fears to the nearby residents that the level of disturbance may increase. Due to wind loading, the foundation of a wind turbine interacts with the soil and creates micro-seismic surface waves that propagate for long distances and they are able to influence adversely sensitive measurements conducted by laboratories located far from the excitation point. A numerical study on the creation and propagation of those waves to the surrounding area is the subject of the present work. Besides, the contribution of those waves to airborne sound generated by the soil-air interaction is also investigated. All numerical simulations are performed with the aid of the Boundary Element Method (BEM), which is ideal for solving such problems since it takes automatically into account the radiation conditions of the waves and thus only the soil-foundation interface and the free surface of the surrounding soil are needed to be discretized. Foundation and soil are considered as linearly elastic materials with interfacial bonding. The frequency domain Helmholtz equation is employed for the simulation of acoustic waves. Numerical results dealing with the airborne and soil borne noise propagation and attenuation are presented and disturbances that might be caused to nearby and far-field structures are discussed.

      PubDate: 2017-05-17T15:38:20Z
      DOI: 10.1016/j.soildyn.2017.05.001
      Issue No: Vol. 99 (2017)
       
  • Dynamic geotechnical properties evaluation of a candidate nuclear power
           plant site (NPP): P- and S-waves seismic refraction technique, North
           Western Coast, Egypt
    • Authors: A.M. Abudeif; A.E. Raef; A.A. Abdel Moneim; M.A. Mohammed; A.F. Farrag
      Pages: 124 - 136
      Abstract: Publication date: August 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 99
      Author(s): A.M. Abudeif, A.E. Raef, A.A. Abdel Moneim, M.A. Mohammed, A.F. Farrag
      Determination of the dynamic geotechnical properties and Vs30 of soil and rocks from seismic wave velocities serves as essential inputs for a foundation design cognizant of seismic site response and rock strength. This study evaluates a site which was suggested for a Nuclear Power Plant (NPP) in El-Dabaa area, north western coast of Egypt. On the near subsurface geology is made up of a thick succession of limestone overlain by a thin layer of soft soil. Assessment of geotechnical materials and Vs30 of the near sub-surface lithological layers are required for design of the foundation of critical structures like turbo-generator and reactor buildings. Interpretation of ninety one shallow P-waves and S-waves seismic refraction profiles distributed within the study area in conjunction with data of 76 boreholes were undertaken to delineate the dynamic properties of shallow soil for construction NPP. The velocity of the P- and S-waves were acquired and interpreted using SeisImager Software Package, then the results were used to build a velocity-depth model to estimate the depth to the bedrock and the thicknesses of overburden layers. This model was verified using boreholes data dissected the seismic profiles to improve the final velocity depth model. The depth to bedrock was determined from both shallow seismic refraction profiles and boreholes. Vs30, elastic moduli and dynamic geotechnical parameters were calculated and the site was classified as a National Earthquake Hazard Reduction Program (NEHRP) class “B”. The values of seismic velocities, the engineering consolidations, and the strength parameters showed that the bedrock in the study area is characterized by more competent rock quality.

      PubDate: 2017-05-17T15:38:20Z
      DOI: 10.1016/j.soildyn.2017.05.006
      Issue No: Vol. 99 (2017)
       
  • Earthquake responses of near-fault building clusters in mountain city
           considering viscoelasticity of earth medium and process of fault rupture
    • Authors: Tielin Liu; Wei Zhong
      Pages: 137 - 141
      Abstract: Publication date: August 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 99
      Author(s): Tielin Liu, Wei Zhong
      A new algorithm is proposed to implement viscoelastic wave propagation in earth medium with surface topography by introducing history variables into integral type GZB constitutive equations and by using the recursive formulae of these history variables. Combining the proposed algorithm with the flexural wave algorithm for frame structure and the algorithm for bidirectional wave propagation, a new type of integrated method is developed for earthquake response analyses of near-fault building clusters in mountain city due to rupture of causative fault. The earthquake responses of building clusters of frame structures situated at different sites of a mountain in Chongqing city, China, are studied during a hypothetical M w 6.2 near-fault earthquake. The numerical results show that, for the multi-story buildings, the maximum peak value of beam-end bending moments appears in the building on the hill top and the earthquake risk positions are mainly at the bottom and/or the top of the buildings. For the high-rise buildings, the maximum peak value of beam-end bending moments appears in the building on the mountainside and the earthquake risk positions are mainly at the bottom and/or the middle of the buildings.

      PubDate: 2017-05-17T15:38:20Z
      DOI: 10.1016/j.soildyn.2017.05.012
      Issue No: Vol. 99 (2017)
       
  • Improving microseismic event and quarry blast classification using
           Artificial Neural Networks based on Principal Component Analysis
    • Authors: Xueyi Shang; Xibing Li; A. Morales-Esteban; Guanghui Chen
      Pages: 142 - 149
      Abstract: Publication date: August 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 99
      Author(s): Xueyi Shang, Xibing Li, A. Morales-Esteban, Guanghui Chen
      The discrimination of microseismic events and quarry blasts has been examined in this paper. To do so, Principal Component Analysis (PCA) and Artificial Neural Networks (ANN) have been used. The procedure proposed has been tested on 22 seismic parameters of 1600 events. In this work, the PCA has been used to transform the original dataset into a new dataset of uncorrelated variables. The new dataset generated has been used as input for ANN and compared to Logistic Regression (LR), Bayes and Fisher classifiers, which classify microseismic events and quarry blasts. The results have shown that PCA is effective for rating variables and reducing data dimension. Furthermore, the classification result based on PCA has been better than those based Ref. [22] and without PCA methods. Moreover, the ANN classifier has obtained the best classification result. The Matthew's Correlation Coefficient (MCC) results of the PCA, Ref. [22] and without PCA based methods have reached 89.00%, 73.68% and 82.04%, respectively, thus showing the reliability and potential of the PCA based method.

      PubDate: 2017-05-17T15:38:20Z
      DOI: 10.1016/j.soildyn.2017.05.008
      Issue No: Vol. 99 (2017)
       
  • Earthquake probability in Taipei based on non-local model with limited
           local observation: Maximum likelihood estimation
    • Authors: J.P. Wang; Yun Xu; Yih-Min Wu
      Pages: 150 - 156
      Abstract: Publication date: August 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 99
      Author(s): J.P. Wang, Yun Xu, Yih-Min Wu
      Many earthquake empirical models were developed based on the statistics in the past. However, it is commonly seen that a non-local model was applied to a local study without any adjustment. In this paper, a new algorithm using maximum likelihood estimation (MLE) to adjust a non-local model for local applications was presented, including a case study assessing the probability of major earthquake occurrences in Taipei. Specifically, considering the fault length of 36km and slip rate of 2mm/yr, it suggests the Sanchiao (or Shanchiao) fault could induce a major earthquake with magnitude M w 7.14±0.17, based on a non-local model integrated with limited local data using the MLE algorithms.

      PubDate: 2017-05-17T15:38:20Z
      DOI: 10.1016/j.soildyn.2017.05.009
      Issue No: Vol. 99 (2017)
       
  • 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)
       
  • Sensitivity study on the discretionary numerical model assumptions in the
           seismic assessment of existing buildings
    • Authors: M. Pianigiani; V. Mariani
      Pages: 155 - 165
      Abstract: Publication date: July 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 98
      Author(s): M. Pianigiani, V. Mariani
      In this work the main assumptions to be made in the seismic assessment of existing RC buildings have been assessed, in order to evaluate how much each of them can affect the obtained evaluation of the building safety, with reference to a case-study structure. Eurocode 8 provides all the information needed to perform the seismic assessment of existing buildings. Even if all the provided prescriptions are followed, in several assumptions a large subjectivity is left to the engineer in charge of the analysis. In this work the scatter related to such choices is evaluated with reference to a case-study building: a real RC Italian building currently used as a hospital. The contemplated assumptions concern the material characterization, the seismic input definition, the type of performed analysis and the set-up of the numerical model adopted to be representative of the building behaviour. The effects of each of these assumptions have been assessed in terms of scatter induced in the assumed response parameters, in order to evaluate the role of the discretionary choices in the seismic assessment. The results presented in this paper are representative of the analysed case-study building only, but aim at putting a spotlight to the effect that some too discretional prescriptions of the technical codes can have on the seismic assessment of existing structures.

      PubDate: 2017-05-01T19:03:34Z
      DOI: 10.1016/j.soildyn.2017.04.001
      Issue No: Vol. 98 (2017)
       
  • Seismic microzoning in Skopje, Macedonia
    • Authors: V.W. Lee; M.D. Trifunac; B.D. Bulajić; M.I. Manić; D. Herak; M. Herak; G. Dimov
      Pages: 166 - 182
      Abstract: Publication date: July 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 98
      Author(s): V.W. Lee, M.D. Trifunac, B.D. Bulajić, M.I. Manić, D. Herak, M. Herak, G. Dimov
      Seismic microzonation maps for Skopje (Macedonia) are presented based on the Uniform-Hazard-Spectrum (UHS) methodology. UHS satisfies the guidelines for performance-based design (PBD), which require 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 considers the contributions from large distant earthquakes and includes simultaneous effects of site geology and site soils. The maps presented include the effects of near and distant large earthquakes in a balanced way, spatial distribution of seismic activity, site geology, and site soil properties.

      PubDate: 2017-05-01T19:03:34Z
      DOI: 10.1016/j.soildyn.2017.04.007
      Issue No: Vol. 98 (2017)
       
  • Experimental study on damping characteristics of soil-structure
           interaction system based on shaking table test
    • Authors: Zhiying Zhang; Hongyang Wei; Xin Qin
      Pages: 183 - 190
      Abstract: Publication date: July 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 98
      Author(s): Zhiying Zhang, Hongyang Wei, Xin Qin
      Soil-structure interaction (SSI) system is composed of soil and structure that are two materials with quite different damping behaviors and it is regarded as non-classical damping system in conventional concept. Based on the analysis of motion state of SSI system, the paper presents the damping characteristic of SSI system via shaking table test. The results of transfer function, acceleration response time histories and equivalent viscous damping ratio and so on indicate that under certain conditions, SSI system shows approximate classical damping characteristic. In practical projects, dynamical analysis of SSI system can be viewed as approximately classical damping system once the synergistic effect of soil is considered.

      PubDate: 2017-05-01T19:03:34Z
      DOI: 10.1016/j.soildyn.2017.04.002
      Issue No: Vol. 98 (2017)
       
  • Analysis of transient wave scattering and its applications to site
           response analysis using the scaled boundary finite-element method
    • Authors: Mohammad Hossein Bazyar; Chongmin Song
      Pages: 191 - 205
      Abstract: Publication date: July 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 98
      Author(s): Mohammad Hossein Bazyar, Chongmin Song
      In this paper, the problem of scattering and amplification of seismic waves by topographical and geological irregularities is addressed directly in the time domain through the scaled boundary finite-element method (SBFEM). The quadtree domain decomposition technique is utilized for the SBFEM discretization of the near field. The far field is rigorously modeled by the displacement unit-impulse response matrix. The computational cost of analyses is reduced through using local formulations in space and time. Considering incident fields of obliquely plane waves coming from far field, the seismic wave inputs are formulated as boundary tractions applied to the near field. Implementing all these aspects in the SBFEM, leads to an elegant technique for time-domain modeling of seismic wave propagation in heterogeneous media with topographical irregularities. Four numerical examples considering various site effects and wave patterns demonstrate the accuracy, versatility and applicability of the approach. The approach is straightforwardly applicable to nonlinear and 3D wave scattering problems with complex site effects.

      PubDate: 2017-05-01T19:03:34Z
      DOI: 10.1016/j.soildyn.2017.04.010
      Issue No: Vol. 98 (2017)
       
  • Residual displacement demands of conventional and dual oscillators
           subjected to earthquake ground motions characteristic of the soft soils of
           Mexico City
    • Authors: Héctor Guerrero; Jorge Ruiz-García; Tianjian Ji
      Pages: 206 - 221
      Abstract: Publication date: July 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 98
      Author(s): Héctor Guerrero, Jorge Ruiz-García, Tianjian Ji
      This paper presents a statistical evaluation of residual displacement (RDs) demands in conventional and dual single-degree-of-freedom (SDOF) oscillators subjected to a set of 220 earthquake ground motions recorded at soft soil sites of Mexico City. A dual SDOF oscillator represents a highly-dissipating energy system (e.g. buckling-restrained braces, BRBs) acting in parallel with a conventional system (e.g. flexible moment-resisting frames). To provide a context, RDs were normalised with respect to the corresponding: a) maximum transient displacements, and b) elastic spectral displacement. The effects of post-yield stiffness ratio (as affected by P-Δ effects), normalised period of vibration with respect to the predominant period of the ground motion, the type of hysteretic response, maximum displacement ductility, lateral strength ratio, type of transition (from elastic-to-plastic response), and damping ratio on normalised RDs were examined for the conventional oscillators. In addition, the effects of the stiffness ratio, lateral strength ratio, displacement ductility, post-yielding stiffness ratio, and type of hysteretic response of the primary and secondary parts of dual SDOF oscillators on normalised RDs were also evaluated. From the results of this investigation, it was observed that for dual SDOF systems the amplitude of normalised RDs is small when the primary part remains elastic. On the contrary, if the primary part exhibits inelastic response, normalised RDs might increase significantly and the post-yielding stiffness ratio of the secondary part plays a key role for constraining them (i.e. while a positive value reduces RDs significantly; a negative value is highly detrimental). Also, it was found that the type of hysteretic response of the primary part of a dual system has a significant effect on normalised RDs (e.g. it was found that a primary part with self-centring capacity, acting in parallel with a highly dissipation system (e.g. BRBs) as secondary part, is very effective for diminishing RDs). A discussion section is also offered to highlight the new findings of this study and differences on normalised RD demands between soft and stiff soils.

      PubDate: 2017-05-01T19:03:34Z
      DOI: 10.1016/j.soildyn.2017.04.014
      Issue No: Vol. 98 (2017)
       
  • Fragility curves for RC frames under multiple earthquakes
    • Authors: F. Hosseinpour; A.E. Abdelnaby
      Pages: 222 - 234
      Abstract: Publication date: July 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 98
      Author(s): F. Hosseinpour, A.E. Abdelnaby
      This study aims to overcome previous limitations and derive fragility curves for three RC (reinforced concrete) buildings with different number of stories under multiple earthquakes. As-recorded seismic sequences in different regions around the world are employed and fiber-based modeling approach that captures degradation in concrete and reinforcing steel materials is used. The results indicate that considering damage from previous events, number of stories, and earthquake region significantly affect fragility curves.

      PubDate: 2017-05-01T19:03:34Z
      DOI: 10.1016/j.soildyn.2017.04.013
      Issue No: Vol. 98 (2017)
       
  • Seismic failure analysis for a high concrete face rockfill dam subjected
           to near-fault pulse-like ground motions
    • Authors: Degao Zou; Huichao Han; Jingmao Liu; Dixiong Yang; Xianjing Kong
      Pages: 235 - 243
      Abstract: Publication date: July 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 98
      Author(s): Degao Zou, Huichao Han, Jingmao Liu, Dixiong Yang, Xianjing Kong
      In the strong seismic zone of Western China, many high concrete face rockfill dams (CFRDs) have been built or designed, and some of these high dams are located in the near-fault region. A near-fault earthquake has relatively long velocity and displacement pulse periods, and a dynamic directivity effect could result in dam failure. However, there are few seismic analysis of high CFRDs considering pulse-like effect. Therefore, it is necessary to investigate the dynamic response of high CFRDs in the near-fault area. In this study, 16 ground motions are selected including 8 pulse-like motions with rupture forward directivity effects and 8 non-pulse motions. The rockfill materials are described using a generalized plasticity model, while a plastic damage model that considers stiffness degradation and strain softening is used to simulate the face slabs. Furthermore, the interfaces between the face slabs and cushions are modeled using interface elements that follow a generalized plasticity model to describe the relative sliding between slab and rockfill. The numerical analysis results indicate that although the near-fault pulse-like ground motion has a moderate impact on the dam acceleration, it has a remarkable impact on the residual deformation of dam and concrete slab damage, especially for the dam crest. The seismic response of the dam increases with an increasing ratio of the peak ground velocity to the peak ground acceleration (PGV/PGA). In addition, even with the similar Arias intensity, the residual deformation of the dam under pulse-like records is larger than those under non-pulse ones. The pulse-like ground motion often generates a high input energy which will cause large deformation of concrete face slab in a short period of time. Therefore, when a CFRD is constructed in the vicinity of an earthquake, the effects of the pulse-like ground motion should be investigated to comprehensively evaluate the seismic safety of the dam.

      PubDate: 2017-05-07T15:22:52Z
      DOI: 10.1016/j.soildyn.2017.03.031
      Issue No: Vol. 98 (2017)
       
  • Effects of SSI and lining corrosion on the seismic vulnerability of
           shallow circular tunnels
    • Authors: Sotirios Argyroudis; Grigorios Tsinidis; Filippo Gatti; Kyriazis Pitilakis
      Pages: 244 - 256
      Abstract: Publication date: July 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 98
      Author(s): Sotirios Argyroudis, Grigorios Tsinidis, Filippo Gatti, Kyriazis Pitilakis
      The paper presents a numerical approach for the construction of seismic fragility curves for shallow metro tunnels considering the soil-structure-interaction (SSI) and the aging effects due to corrosion of the lining reinforcement. The tunnel response under ground shaking is evaluated through 2D non-linear dynamic analyses, for increasing levels of seismic intensity. An elasto-plastic model is used to simulate the soil non-linear behavior under ground shaking, while the effects of lining mechanical properties, soil conditions and ground motion characteristics are also accounted for. The effect of corrosion on the lining behavior is encountered through proper modification of the lining strength properties. Damage state thresholds are defined based on the exceedance of the lining capacity. The fragility curves are estimated in terms of peak ground acceleration at the ground free field conditions for different time periods considering the associated uncertainties. The proposed approach is applied for the fragility assessment of selected soil-tunnel configurations. The derived fragility functions are compared with existing empirical and analytical fragility models, highlighting the important role of soil conditions and corrosion effects in the vulnerability of tunnel structures. The proposed fragility models contribute towards an advanced vulnerability and risk assessment of transportation systems and infrastructures.

      PubDate: 2017-05-07T15:22:52Z
      DOI: 10.1016/j.soildyn.2017.04.016
      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)
       
  • Evaluation of dynamic properties of sandy soil at high cyclic strains
    • Abstract: Publication date: August 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 99
      Author(s): Shiv Shankar Kumar, A. Murali Krishna, Arindam Dey
      Dynamic loading conditions, such as earthquakes, may result in the generation of high shear strain (>5%) in the soil. Conventionally, dynamic properties of soils are estimated from the tests conducted up to a shear strain of 1% by considering Symmetrical Hysteresis Loop (SHL). However, it is commonly observed that the hysteresis loops become progressively asymmetric with increasing shear strain, which leads to the over- or under-estimation of the conventionally evaluated dynamic properties. Hence, it is necessary to adopt a modified methodology of evaluating the dynamic properties of saturated sands based on the actual Asymmetrical Hysteresis Loop (ASHL). Strain-controlled cyclic triaxial tests have been conducted, for a peak shear strain range of 0.015–4.5% at 1Hz loading frequency, on test specimens prepared at different relative density (30–90%) and confining stress (50–150kPa). Although, the shear modulus evaluated considering SHL and ASHL are on close agreement, the damping ratio evaluated considering SHL is approximately 40–70% lesser than that obtained by considering ASHL. Moreover, in contrast to the classical curves as largely applied in geotechnical engineering, a noticeable decrement of the damping ratio is observed beyond 0.75% shear strain.

      PubDate: 2017-05-23T15:13:39Z
       
  • Dynamic 2.5D Green's functions for moving distributed loads acting on an
           inclined line in a multi-layered TI half-space
    • Abstract: Publication date: August 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 99
      Author(s): B.A. Zhenning, W. Lee Vincent, Liang Jianwen, Yan Yang
      Dynamic two and a half dimensional (2.5D) Green's functions for a multi-layered transversely isotropic (TI) half-space are developed by using the dynamic stiffness method combining with the inverse Fourier transform. The 2.5D Green's functions correspond to solutions of uniformly distributed loads acting on part of a multi-layered TI half-space on a line which is inclined to the horizontal and moving along a horizontal straight line with a constant speed. Solutions in the frequency and wavenumber domains are first obtained, which are expressed as the summation of the responses restricted in the loaded layer and of the corresponding reaction forces. Results in the time and space domains are then recovered by Fourier synthesis of the frequency and wavenumber responses which in turn are obtained by numerical integration over on one horizontal wavenumber. The derived Green's functions are verified through comparison with the existing solutions for the isotropic medium that is a special case of the more general problem addressed. Parametric studies are performed in both the frequency and time domains, which show that dynamic responses are highly related to the TI parameters, the load frequency, the load speed and the TI layer. In addition, as an application example, these Green's functions combined with the indirect boundary element method (IBEM) are used to solve the 3D wave scattering of a 2D tunnel embedded in a multi-layered TI half-space. Comparison between the obtained surface displacement amplitudes with those of de Barros and Luco [12] for the isotropic case reinforces the validity and reliability of the presented formulations.

      PubDate: 2017-05-23T15:13:39Z
       
  • On seismic vulnerability of highway bridges in Nepal: 1988 Udaypur
           earthquake (MW 6.8) revisited
    • Abstract: Publication date: August 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 99
      Author(s): Dipendra Gautam
      Highway bridges are one of the most important components of transportation system thus continuous operability is expected even after strong to major earthquakes. Nepal is situated in one of the most active seismic regions in the world and devastating earthquakes are frequent, however, to the best knowledge of the author, fragility functions for Nepali highway bridges do not exist until now. This paper is a first attempt to depict the seismic vulnerability of highway bridges in Nepal. Observational data from 1988 Udaypur earthquake were adopted to construct fragility functions for minor damage state DS1. Comparison between the constructed fragility curve with other observational fragility curves for similar damage state highlighted that Nepali highway bridges can be affected minor damage even in very low peak ground acceleration.

      PubDate: 2017-05-23T15:13:39Z
       
  • Editorial Board / Aims and Scope
    • Abstract: Publication date: July 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 98


      PubDate: 2017-05-17T15:38:20Z
       
 
 
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