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EARTH SCIENCES (466 journals)

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Journal Cover Soil Dynamics and Earthquake Engineering
  [SJR: 1.516]   [H-I: 56]   [15 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0267-7261
   Published by Elsevier Homepage  [3043 journals]
  • Performance-based assessment of protection measures for buried pipes at
           strike-slip fault crossings
    • Authors: Vasileios E. Melissianos; Dimitrios Vamvatsikos; Charis J. Gantes
      Pages: 1 - 11
      Abstract: Publication date: October 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 101
      Author(s): Vasileios E. Melissianos, Dimitrios Vamvatsikos, Charis J. Gantes
      Onshore buried steel pipelines are vulnerable to fault rupture, where large ground displacements are imposed on the crossing pipe and thus protection measures are often necessary to avoid failure. A three-step methodology based on the framework of performance-based earthquake engineering is presented on assessing the effectiveness of protection measures against the consequences of strike-slip faulting on pipes. Firstly, the randomness of the fault movement is quantified, next the pipeline mechanical behavior is numerically assessed and finally the results are combined to extract the strain hazard curves, which are easy-to-handle engineering decision making tools. The various protection measures used in engineering practice or proposed in the literature are evaluated through the mean annual rate of exceeding strain values, also including a simple safety checking format at the strain level. Conclusions are extracted from the proposed assessment methodology on the efficiency of measures with reference to engineering practice and safety requirements of the pipeline operator.

      PubDate: 2017-07-24T12:37:51Z
      DOI: 10.1016/j.soildyn.2017.07.004
      Issue No: Vol. 101 (2017)
       
  • Coupled influence of content, gradation and shape characteristics of silts
           on static liquefaction of loose silty sands
    • Authors: Mehmet Murat Monkul; Ehsan Etminan; Aykut Şenol
      Pages: 12 - 26
      Abstract: Publication date: October 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 101
      Author(s): Mehmet Murat Monkul, Ehsan Etminan, Aykut Şenol
      Static liquefaction is a challenging problem of geotechnical engineering as its consequences are generally catastrophic when they occur on site. Previous laboratory studies focused on various factors that could influence the static liquefaction potential of silty sands. Most popular of those investigated factors are stress conditions, deposition method and fines content. The purpose of the present study is to investigate the other possible factors, of which very little is known, mainly focusing on the silt characteristics including grain size distribution, relative size, and shape effects of the silt grain matrix within the sand. Undrained monotonic triaxial compression tests were conducted on thirty sands with varying fines contents, which were prepared by mixing three base sands (Sile Sands 20/30, 50/55, 80/100) with same geologic origin but with different gradations and three different non-plastic silts (IZ, SI and TT silts) with different gradations and shape characteristics. The experimental results revealed that each of the mentioned factors had their own influence on static liquefaction behavior of sands. The static liquefaction potential of all the three sands in this study was observed to increase with decreasing coefficient of uniformities of the silt grain matrix (CUsilt) in sands. For a particular base sand, static liquefaction potential was observed to increase with decreasing mean grain diameter ratio (D50-sand/d50-silt) due to change of silt gradation. However, shape characteristics of the silt grains are also found to be another important factor, in certain cases observed to have a greater influence than mean grain diameter ratio criterion. As an example, it was shown that at the same FC, base sand, depositional energy and consolidation stress, angular nature of TT silt potentially caused more meta-stable contacts (weaker grain contacts that promote excess pore pressure generation during shearing) within the specimens than sub-rounded SI silt, which caused specimens with TT silt to be more liquefiable than their counterparts with SI silt. Moreover, it was found that there is a coupled relationship between the fines content and investigated silt characteristics (gradation, mean size, shape effects) on the static liquefaction behavior of sands. The unexpected trend regarding the last finding is that the mentioned influence of silt characteristics (i.e. gradation, size and shape) on static liquefaction of sands becomes more considerable with decreasing fines content at loose states.

      PubDate: 2017-08-02T23:57:33Z
      DOI: 10.1016/j.soildyn.2017.06.023
      Issue No: Vol. 101 (2017)
       
  • Newmark sliding block model for predicting the seismic performance of
           vegetated slopes
    • Authors: T. Liang; J.A. Knappett
      Pages: 27 - 40
      Abstract: Publication date: October 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 101
      Author(s): T. Liang, J.A. Knappett
      This paper presents a simplified procedure for predicting the seismic slip of a vegetated slope. This is important for more precise estimation of the hazard associated with seismic landslip of naturally vegetated slopes, and also as a design tool for determining performance improvement when planting is to be used as a protective measure. The analysis procedure consists of two main components. Firstly, Discontinuity Layout Optimisation (DLO) analysis is used to determine the critical seismic slope failure mechanism and estimate the corresponding yield acceleration of a given slope. In DLO analysis, a modified rigid perfectly plastic (Mohr–Coulomb) model is employed to approximate small permanent deformations which may accrue in non-associative materials when subjected to ground motions with relatively low peak ground acceleration. The contribution of the vegetation to enhancing the yield acceleration is obtained via subtraction of the fallow slope yield acceleration. The second stage of the analysis incorporates the vegetation contribution to the slope's yield acceleration from DLO into modified limit equilibrium equations to further account for the geometric hardening of the slope under increasing soil movement. Thereby, the method can predict the permanent settlement at the crest of the slope via a slip-dependent Newmark sliding block approach. This procedure is validated against a series of centrifuge tests to be highly effective for both fallow and vegetated slopes and is subsequently used to provide further insights into the stabilising mechanisms controlling the seismic behaviour of vegetated slopes.

      PubDate: 2017-08-02T23:57:33Z
      DOI: 10.1016/j.soildyn.2017.07.010
      Issue No: Vol. 101 (2017)
       
  • Framework for the vulnerability assessment of structure under
           mainshock-aftershock sequences
    • Authors: Weiping Wen; Changhai Zhai; Duofa Ji; Shuang Li; Lili Xie
      Pages: 41 - 52
      Abstract: Publication date: October 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 101
      Author(s): Weiping Wen, Changhai Zhai, Duofa Ji, Shuang Li, Lili Xie
      Many earthquakes have indicated that the mainshock-damaged structures may be more vulnerable to severe damage and collapse during the subsequent aftershocks. This manuscript presents a framework for the vulnerability assessment of structure under the mainshock-aftershock sequences. In this framework, the engineering demand parameter (EDP) which can more effectively characterized the additional damage of structure induced by aftershock, and the intensity measure (IM) having the higher correlation with the additional damage of structure are selected and used. The versatility of the proposed framework is demonstrated on a case-study reinforced concrete (RC) frame structure with 5 stories. The influences of aftershocks on the fragility of structure are studied for different limit states. The effects of aftershocks on the fragility of structure are more obvious for the case that mainshock fragility changes from 30% to 60%, and the maximum influence of aftershock can exceed 15%. The results in this study can be used to evaluate the vulnerability of structure under the seismic sequence in the pre-earthquake environment.

      PubDate: 2017-08-02T23:57:33Z
      DOI: 10.1016/j.soildyn.2017.07.002
      Issue No: Vol. 101 (2017)
       
  • Response of steel moment and braced frames subjected to near-source
           
    • Authors: Pouria Ayough; Seiyed Ali Haj Seiyed Taghia
      Pages: 53 - 66
      Abstract: Publication date: October 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 101
      Author(s): Pouria Ayough, Seiyed Ali Haj Seiyed Taghia
      Most seismic regulations are usually associated with fixed-base structures, assuming that elimination of this phenomenon leads to conservative results and engineers are not obliged to use near-fault earthquakes. This study investigates the effect of soil–structure interaction on the inelastic response of MDOF steel structures by using well known Cone method. In order to achieve this, three dimensional multi-storey steel structures with moment and braced frame are analyzed using non-linear time history method under the action of 40 near-fault records. Seismic response parameters, such as base shear, performance of structures, ductility demand and displacement demand ratios of structures subjected to different frequency-contents of near-fault records including pulse type and high-frequency components are investigated. The results elucidate that the flexibility of soil strongly affects the seismic response of steel frames. soil – structure interaction can increase seismic demands of structures. Also, soil has approximately increasing and mitigating effects on structural responses subjected to the pulse type and high frequency components. A threshold period exists below which can highly change the ductility demand for short period structures subjected to near-fault records.

      PubDate: 2017-08-02T23:57:33Z
      DOI: 10.1016/j.soildyn.2017.07.013
      Issue No: Vol. 101 (2017)
       
  • Optimum earthquake-tuned TMDs: Seismic performance and new design concept
           of balance of split effective modal masses
    • Authors: Jonathan Salvi; Egidio Rizzi
      Pages: 67 - 80
      Abstract: Publication date: October 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 101
      Author(s): Jonathan Salvi, Egidio Rizzi
      The present paper, concerning the performance of optimum TMDs in seismic engineering, is composed of two parts. First, Part I deals with a comprehensive investigation on the effectiveness of an optimum seismic-tuned TMD towards reducing the earthquake response of linear frame structures, which is set up by a dedicated optimisation algorithm, allowing to achieve the best control device for a specific structural system and earthquake event. First, a representative set of 16 primary structures and 18 selected earthquakes has been considered, for a total of 288 cases. Second, additional trials based on a benchmark 10-storey frame and on a codified set of far-field earthquakes (FEMA P695 database), composed of 2×22=44 records, have been developed, for a further assessment. The presented outcomes provide extensive information about the TMD performance in the seismic engineering scenario, for a-priori known seismic input. Then, Part II reports a comprehensive post-processing and interpretation analysis of the results above. Specifically, connections between seismic TMD performance and modal structural properties are envisaged. Cross-comparisons, presented here through typical sample cases, analyse the changes of the structural characteristics after TMD insertion and monitor the associated effects on the seismic response reduction. The crucial role of achieving a balanced split of effective modal masses on the tuned mode is investigated, and highlighted as an essential ingredient to rely on a high TMD effectiveness in the seismic context. This criterion may be implemented within the tuning process, as a basic true structure-based concept for TMD design in Earthquake Engineering applications, thus for a-priori unknown seismic input.

      PubDate: 2017-08-02T23:57:33Z
      DOI: 10.1016/j.soildyn.2017.05.029
      Issue No: Vol. 101 (2017)
       
  • Vulnerability and recovery time evaluation of an enhanced urban overpass
           foundation
    • Authors: Juan M. Mayoral; Adriana Badillo; Mauricio Alcaraz
      Pages: 1 - 15
      Abstract: Publication date: September 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 100
      Author(s): Juan M. Mayoral, Adriana Badillo, Mauricio Alcaraz
      This paper presents a vulnerability assessment and recovery time evaluation of two critical supports of a 23.5km long urban overpass built in stiff soil, in the northeast Mexico City area. The evaluations were carried out considering both normal and subduction fault events expressed in terms of uniform hazard spectra for several return periods. Probabilistic site response analyses, and site specific numerically-derived fragility curves were used to assess the critical supports probability of reaching or exceeding a given damage state, considering two foundation types: a conventional raft foundation structurally connected to four precast-end bearing concrete piles, and a so-called enhanced massive foundation. The seismic response of each foundation system was characterized using series of 3-D finite elements models developed with the program SASSI2000 for increasing seismic intensity levels. The effect of both soil conditions and ground motion characteristics on the soil-structure system response was accounted for in the analyses. The damage index was defined in terms of earthquake induced transversal and longitudinal pier displacements, which was associated with column cracking, and potential loss of support of the upper deck. The vulnerability and reduction on recovery times for the foundation alternative was established.

      PubDate: 2017-05-27T15:27:08Z
      DOI: 10.1016/j.soildyn.2017.05.023
      Issue No: Vol. 100 (2017)
       
  • Seismic demand and experimental evaluation of the nonstructural building
           curtain wall: A review
    • Authors: Baofeng Huang; Shiming Chen; Wensheng Lu; Khalid M. Mosalam
      Pages: 16 - 33
      Abstract: Publication date: September 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 100
      Author(s): Baofeng Huang, Shiming Chen, Wensheng Lu, Khalid M. Mosalam
      This paper reviews the existing studies related to seismic demand and experimental investigation of the nonstructural building curtain wall (CW). Being treated as a nonstructural component, seismic performance of the building CW relates to its seismic demand parameters, i.e., acceleration and drift demands. In current code provisions, the acceleration demand consists of the floor acceleration amplification factor, component acceleration amplification factor, component importance factor, and component response modification factor, which are all based on or induced by the floor response and dynamic response of the CW itself. For the CW which is attached to the main structure, drift demand is an indication of the interstory drift ratio. The in-plane seismic drift mechanism of the framed glass CW was fully developed, and the corresponding static testing protocols were implemented in codes based on several past experimental studies. Shaking table testing of the CW was conducted as well, where the input motions need specific floor response analysis of the main structure. The relevant damage state definition and fragility curve development are important to represent the performance and damage level of the CW system. The philosophy of the performance-based earthquake engineering (PBEE) and its application to CW are elaborated, and possible challenges related to the seismic demand, experimental studies, and PBEE of the CW are addressed as well.

      PubDate: 2017-05-27T15:27:08Z
      DOI: 10.1016/j.soildyn.2017.05.025
      Issue No: Vol. 100 (2017)
       
  • Ferrous SMA (FNCATB) based Superelastic Friction Bearing Isolator (S-FBI)
           subjected to pulse type ground motions
    • Authors: Sutanu Bhowmick; Sudib Kumar Mishra
      Pages: 34 - 48
      Abstract: Publication date: September 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 100
      Author(s): Sutanu Bhowmick, Sudib Kumar Mishra
      A new variant of ferrous Shape Memory Alloy with Fe-Ni-Co-Al-Ta-B (FNCATB) composition have been proposed that shows huge superelasticity under a wide temperature range. This shows the potential as a much superior and economic alternative for seismic applications. With this as the eventual goal, the FNCATB wires are employed as restrainers in conjunction with the pure-friction bearing, referred as super-elastic Friction Base Isolator (S-FBI). The FNCATB based S-FBI shows superior performance over the conventional Frictional Pendulum System (FPS) and the Nitinol based S-FBI, with a much less (1/17-th) volume requirement, estimated from the pertinent isolator parameters, the optimal choice of which are obtained through ad hoc optimization. The performance assessment is based on nonlinear dynamic analysis under a suite of recorded near-fault ground motions. An experimental force-deformation dataset for the FNCATB are fitted in the existing Wilde's model to describe the super-elasticity. The FNCATB S-FBI offers considerable improvement, either in the isolation efficiency or reducing the base displacement with slight or no compromise in the other. The performances are also supported by a set of performance indices adopted from benchmark seismic control problem. An energetic assessment also corroborate to these findings. A Short Time Fourier Transform (STFT) based analysis of floor accelerations demonstrate the superior high frequency suppression characteristics of the FNCATB over the Friction Pendulum System (FPS) and Nitinol based S-FBI. The ferrous composition while coupled with less volume requirement implies to superior economic viability that can be studied through detailed cost-benefit analysis.

      PubDate: 2017-05-27T15:27:08Z
      DOI: 10.1016/j.soildyn.2017.03.037
      Issue No: Vol. 100 (2017)
       
  • On the accuracy of the N2 inelastic spectrum for timber structures
    • Authors: Giovanni Rinaldin; Massimo Fragiacomo; Claudio Amadio
      Pages: 49 - 58
      Abstract: Publication date: September 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 100
      Author(s): Giovanni Rinaldin, Massimo Fragiacomo, Claudio Amadio
      Timber buildings in earthquake prone regions must be designed to withstand the seismic actions. The N2 method, already employed in the Eurocode 8 to check the seismic resistance of a building employing its capacity curve, uses inelastic spectra calculated on the basis of the system ductility. Such a procedure was extensively used for the design of steel and reinforced concrete structures. Timber structures, however, have a different and more complex hysteretic behaviour characterized by significant pinching, strength degradation and softening. Consequently, the current version of the N2 proposed spectrum may be inadequate for the design of timber systems. This paper investigates the accuracy of the N2 spectrum for timber structures by calculating the ‘rigorous’ inelastic spectra for natural seismic records selected to match, with their average, a chosen design elastic spectrum. A purposely developed software has been used to obtain the inelastic spectra for a Single Degree of Freedom (SDOF) system characterized by a slip-type hysteretic relationship with pinching typical of timber structures. Two different sets of records have been considered: the former is consistent, on average, with a given design spectrum from Eurocode 8, the latter is taken from a strong motion database by selecting the records having soil class A and PGA within a chosen range. Non-linear dynamic analyses have been carried out by varying the level of ductility and the natural vibration period of the SDOF systems. The effects of hardening or softening of the system behaviour have also been analysed. Two analysis procedures have been used with the aim to have a further confirmation of the achieved results. The comparisons between the rigorous and the approximated N2 spectrum demonstrate that, in general, the N2 method always give fairly good results in estimating the inelastic spectra even for timber structures.

      PubDate: 2017-05-27T15:27:08Z
      DOI: 10.1016/j.soildyn.2017.05.026
      Issue No: Vol. 100 (2017)
       
  • Dynamic lateral response of suction caissons
    • Authors: C. Latini; V. Zania
      Pages: 59 - 71
      Abstract: Publication date: September 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 100
      Author(s): C. Latini, V. Zania
      Deeper water installations of offshore wind turbines may be supported by jacket structures. This study investigates the dynamic response of suction caissons for jackets by analysing 3D finite element models in the frequency domain. The numerical modelling was firstly validated by analytical solutions for pile foundations. Groups of crucial dimensionless parameters related to the soil profile and the foundation geometry are identified and their effects on the response of suction caissons are studied. Static stiffness coefficients are presented in a form of mathematical formulas obtained by fitting the numerical results, pertaining foundations with different slenderness ratios and embedded in different soil profiles. Sensitivity of the dynamic impedances of suction caissons on the skirt length was showed in this study. Moreover, the results for the suction caissons indicated that the overall dynamic response is profoundly affected by the relative thickness of the soil layer and by the variation of soil stiffness with depth.

      PubDate: 2017-05-27T15:27:08Z
      DOI: 10.1016/j.soildyn.2017.05.020
      Issue No: Vol. 100 (2017)
       
  • Impact of ground motion duration and soil non-linearity on the seismic
           performance of single piles
    • Authors: Alessandro Tombari; M. Hesham El Naggar; Francesca Dezi
      Pages: 72 - 87
      Abstract: Publication date: September 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 100
      Author(s): Alessandro Tombari, M. Hesham El Naggar, Francesca Dezi
      Pile foundations strongly influence the performance of supported structures and bridges during an earthquake. In case of strong earthquake ground motion, soft soils may be subjected to large deformation manifesting aspects typical of the non-linear behaviour such as material yielding, gapping and cyclic degradation. Therefore, nonlinear soil-pile interaction models should be able to capture these effects and improve the prediction of the actual seismic loading transferred from the foundation to the superstructure. In this paper, a beam on nonlinear Winkler foundation (BNWF) model is used, which can simulate cyclic soil degradation/hardening, soil and structural yielding, slack zone development and radiation damping. Incremental Dynamic Analyses (IDAs) are performed to evaluate the effects of Ground Motion Duration (GMD) and soil non-linearity on the performance of single fixed-head floating piles. Various homogeneous and bilayer soil profiles are considered, including saturated clay and sand in either fully dry or saturated state and with different levels of compaction. In order to evaluate the effect of nonlinearity on the response, the results of the nonlinear analyses are compared with those obtained from linear soil-pile analysis in terms of bending moment envelope. Results show the relevance of considering the GMD on the performance of the single pile especially when founded on saturated soils. For low intensities and dry sandy soils, the linear soil-pile interaction model can be used for obtaining reliable results.

      PubDate: 2017-05-27T15:27:08Z
      DOI: 10.1016/j.soildyn.2017.05.022
      Issue No: Vol. 100 (2017)
       
  • Strength and stiffness assessment of railway track substructures using
           crosshole-type dynamic cone penetrometer
    • Authors: Won Taek Hong; Sang Yeob Kim; Sung Jin Lee; Jong Sub Lee
      Pages: 88 - 97
      Abstract: Publication date: September 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 100
      Author(s): Won Taek Hong, Sang Yeob Kim, Sung Jin Lee, Jong Sub Lee
      To ensure safe train services, an effective method is required for the characterization of the strength and stiffness of railway track substructures. In this study, a crosshole-type dynamic cone penetrometer (CDP) is developed to characterize the strength by the crosshole-type dynamic cone penetration index (CDPI) and stiffness by the shear wave velocity (Vs). To verify the Vs obtained using the CDP test, the Vs obtained by both CDP and bender elements are compared in a chamber test. In addition, for the characterization of the railway track substructures, field tests are conducted. The chamber test shows that the Vs obtained using the CDP are almost the same as those obtained by bender elements. In field tests, the CDPI and the Vs are profiled along the depth, the including ballast, sub-ballast, and subgrade layers, which are identified by ground penetrating radar surveys. As the CDPI is highly correlated to the Vs, the stiffness characteristics are considered to be reasonable and can be simply estimated using the CDPI. This study demonstrates that the CDP test can be used for the evaluation of the strength characteristics and small strain elastic properties of the track substructures.

      PubDate: 2017-05-27T15:27:08Z
      DOI: 10.1016/j.soildyn.2017.05.021
      Issue No: Vol. 100 (2017)
       
  • Influence of column shear failure on pushover based assessment of masonry
           infilled reinforced concrete framed structures: A case study
    • Authors: Liborio Cavaleri; Fabio Di Trapani; Panagiotis G. Asteris; Vasilis Sarhosis
      Pages: 98 - 112
      Abstract: Publication date: September 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 100
      Author(s): Liborio Cavaleri, Fabio Di Trapani, Panagiotis G. Asteris, Vasilis Sarhosis
      Structural frames, constructed either of steel or reinforced concrete (RC), are often infilled with masonry panels. However, during the analysis of the structural frames, it has become common practice to disregard the existence of infills because of the complexity in modeling. This omission should not be allowed because the two contributions (of infills and of frames) complement each other in providing a so different structural system. The use of different modeling assumptions significantly affects the capacity as well as the inelastic demand and safety assessment. In specific, the adoption of equivalent diagonal pin-jointed struts leaves open the problem of the evaluation of the additional shear on columns and consequently of the choice of a proper eccentricity for the diagonal struts. In this context, this paper presents the results of a real case study. The seismic performance of the RC structure of a school is evaluated by using concentric equivalent struts for modeling infills and the level of the additional shear on the columns is fixed as a rate of the axial force on them in agreement to a strong correlation obtained after a numerical experimentation. Hence, the applicability of the correlation mentioned before is shown and the form in which the results can be provided is presented. The characteristics of the new approach, first time applied to a real case, are highlighted by a comparison between the performance obtainable with different modeling detail levels of the infills. Through the paper, it is proved that the simplified evaluation of the additional shear demand produced by infills just for the base columns is sufficient to warn that a simplified model disregarding infills or based on the use of concentric struts for the infills may considerably overestimate the structural capacity. Further, by the study of a real case, the paper provides an overview of the models developed by the authors to obtain the capacity of reinforced concrete framed structure for the practical applications.

      PubDate: 2017-06-12T11:48:31Z
      DOI: 10.1016/j.soildyn.2017.05.032
      Issue No: Vol. 100 (2017)
       
  • Experimental validation of a model for seismic simulation and interaction
           analysis of buried pipe networks
    • Authors: Wei Liu; Huiquan Miao; Chuang Wang; Jie Li
      Pages: 113 - 130
      Abstract: Publication date: September 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 100
      Author(s): Wei Liu, Huiquan Miao, Chuang Wang, Jie Li
      A finite-element model is established to evaluate the seismic responses of buried pipe networks. In the model, pipes are simulated as beams on elastic foundation, the joints of the segmented pipes are modeled by axial and rotational springs, and the pipe–soil interactions are simulated by springs. The seismic wave acts on one end of the soil springs to induce the seismic responses of the pipe networks. The test results of a buried pipe network subjected to an artificial earthquake is adopted as benchmark to validate the model. The tested pipe network has a size of 24m×24m and consists of ductile cast iron and welded steel pipes. The artificial earthquake is produced by 30kg of TNT explosives. Two important responses are compared, i.e., the joint deformations of the ductile cast iron pipes and the strains of the welded steel pipes. Results indicate that the model can evaluate the seismic responses of the buried pipe networks well. The pipe interactions are analyzed using the model by comparing the seismic responses of the single pipe and its counterpart in the pipe network.

      PubDate: 2017-06-12T11:48:31Z
      DOI: 10.1016/j.soildyn.2017.05.024
      Issue No: Vol. 100 (2017)
       
  • Influence of presence of adjacent surface structure on seismic response of
           underground structure
    • Authors: Huai-feng Wang; Meng-lin Lou; Ru-lin Zhang
      Pages: 131 - 143
      Abstract: Publication date: September 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 100
      Author(s): Huai-feng Wang, Meng-lin Lou, Ru-lin Zhang
      A numerical study is made on the dynamic through-soil interaction between underground station and nearby pile supported surface structure on viscous-elastic soil layer, under vertically incident S wave. This paper, as a companion of another paper written by the authors [1], focuses on the influence of presence of adjacent surface structure on seismic response of underground structure, while the reference [1] centers on the influence of presence of adjacent underground structure on seismic response of surface structure. To this end, a commercial software product for finite element analysis, ANSYS, has been further developed and enhanced for calculation in frequency domain, in which hysteretic damping can be considered for both the soil and the structures, so that structure-soil-structure interaction (SSSI) can be investigated by via a direct methodology. A discussion is made on the influence of arrangement of structures, distances between structures, shaking direction of seismic wave, shear wave velocity and damping of soil, scale and burial depth of underground structure, storey number, stiffness, style and pile length of surface structure on SSSI, in terms of horizontal relative displacement of underground structure. Maximum relative displacement responses are also presented for 12 seismic inputs. Arrangement and shaking direction are two of the most important factors. The system response can be either amplified or attenuated according to the distance between adjacent structures, related to dynamic properties of the overall system. Those underground structures, surrounded by buildings with the fundamental frequency approximate to that of free field, are heavily affected.

      PubDate: 2017-06-12T11:48:31Z
      DOI: 10.1016/j.soildyn.2017.05.031
      Issue No: Vol. 100 (2017)
       
  • Sensitivity to modelling and design of curved surface sliding bearings in
           the nonlinear seismic analysis of base-isolated r.c. framed buildings
    • Authors: Fabio Mazza; Mirko Mazza
      Pages: 144 - 158
      Abstract: Publication date: September 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 100
      Author(s): Fabio Mazza, Mirko Mazza
      The main object of this study is to investigate the influence that different modelling assumptions of the curved surface sliding (CSS) bearings may have on the lateral-torsional response of irregular base-isolated structures located in near-fault area, characterized by fling-step and directivity effects with large amplitudes and long period horizontal velocity pulses. The second aim is to evaluate the effects of different design assumptions of the CSS system. To this end, a six-storey base-isolated reinforced concrete (r.c.) framed building, with an L-shaped plan and setbacks in elevation, is designed assuming low- and medium-type friction properties, both with two in-plan distributions of the dynamic-fast friction coefficient, corresponding to: (i) the same value for all isolators; (ii) a different value for each isolator. Four additional cases are compared reducing the friction coefficient in accordance with a temperature increase up to 250°C during ground motions. A computer code for the nonlinear dynamic analysis is developed, in order to compare five models of the CSS bearings that consider constant and variable axial loads combined with constant and variable friction coefficients as function of sliding velocity, axial pressure and stick-slip effect. A lumped plasticity model is used to describe the inelastic behaviour of the superstructure, including a 26-flat surface modelling of the axial load-biaxial bending moment elastic domain at the end sections of r.c. frame members. Near-fault ground motions with significant horizontal components are selected and scaled in line with the design hypotheses adopted for the test structure.

      PubDate: 2017-06-12T11:48:31Z
      DOI: 10.1016/j.soildyn.2017.05.028
      Issue No: Vol. 100 (2017)
       
  • Seismic responses of base-isolated flexible rectangular fluid containers
           under horizontal ground motion
    • Authors: S. Hashemi; M.H. Aghashiri
      Pages: 159 - 168
      Abstract: Publication date: September 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 100
      Author(s): S. Hashemi, M.H. Aghashiri
      This paper focuses on analyzing, the results and arguments about the analysis of seismic base-isolated flexible rectangular containers. An equivalent mechanical model of rectangular containers with three lumped masses and six degrees of freedom is used. Lead rubber bearing (LRB) and friction pendulum system (FPS) are two types of seismic isolators, used to isolate the storage tank base. Results show that seismic base isolation can be an efficient way to reduce seismic responses such as base shear, wall deflection and hydrodynamic pressure, but it can adversely affect the free surface sloshing height. The seismic responses of isolated tanks under unidirectional excitation (No interaction) and bidirectional excitation (Interaction) are not considerably different and the results are not very sensitive to the interaction effect of the bearing forces. In any case, the careful choice of the number and the mechanical characteristics of seismic base isolation systems is suggested to achieve good responses.

      PubDate: 2017-06-12T11:48:31Z
      DOI: 10.1016/j.soildyn.2017.05.010
      Issue No: Vol. 100 (2017)
       
  • Feasibility analysis of using MetaSoil scatterers on the attenuation of
           seismic amplification in a site with triangular hill due to SV-waves
    • Authors: M. Maleki; M.I. Khodakarami
      Pages: 169 - 182
      Abstract: Publication date: September 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 100
      Author(s): M. Maleki, M.I. Khodakarami
      Experimental and theoretical studies show an extra amplification in the site response near topographic irregularities due to seismic waves. The aim of this paper is to assess the implementation of a mass-in-mass periodic external isolator framework based on the concept of metamaterials, termed MetaSoil (MS) in order to reduce the seismic amplification on hills subjected to in-plane waves. A MS prepares a blind frequency zone, where the propagation of waves with this frequency content is excluded. The feasibility of using such systems considering various soil types, aspect ratio of the hill shapes, geometry of MS and excitation frequencies is investigated. In achieving this end, several two-dimensional models by adopting the finite element method and the wave propagation theory are analyzed using a time-history approach. The efficiency of this system is evaluated for each model, with results demonstrating up to 40% attenuation in the strong ground motions on the hills via the use of the proposed lattice.

      PubDate: 2017-06-12T11:48:31Z
      DOI: 10.1016/j.soildyn.2017.05.036
      Issue No: Vol. 100 (2017)
       
  • Evaluation of soil-structure interaction effects on the damping ratios of
           buildings subjected to earthquakes
    • Authors: Cristian Cruz; Eduardo Miranda
      Pages: 183 - 195
      Abstract: Publication date: September 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 100
      Author(s): Cristian Cruz, Eduardo Miranda
      This paper evaluates the effects of soil-structure interaction on damping ratios of buildings subjected to earthquake ground motions. Explicit expressions of transfer functions of absolute horizontal accelerations of multi-story buildings on an elastic half-space subjected to horizontal ground motions are developed. An optimization procedure is then used to obtain the effective modal properties of a replacement or “equivalent” fixed-based multi-story building that minimize the difference in the ordinates of the absolute acceleration transfer functions in the building on flexible-base relative to those in the replacement fixed-base building. A parametric study was conducted to study the variation of effective modal damping ratios of the fundamental mode and of higher modes of vibration with changes on the wave parameter. Results indicate soil-structure interaction effects may either increase or reduce the effective modal damping ratio of the fundamental period. Typically, it reduces the effective damping ratios of slender long period structures such as tall buildings and increases the damping ratio of short and medium period structures. It is shown that the reduction of effective modal damping ratio of the fundamental mode with increasing height computed in this study follows a similar trend to that observed in instrumented buildings, indicating that the reduction in damping ratio observed in buildings as their height increases is primarily due to soil-structure interaction effects. Furthermore, it is shown that soil-structure interaction effects lead to an approximately linear trend in effective modal damping ratios with increasing modal frequency.

      PubDate: 2017-06-12T11:48:31Z
      DOI: 10.1016/j.soildyn.2017.05.034
      Issue No: Vol. 100 (2017)
       
  • Sensitivity of ground motion parameters to local shear-wave velocity
           models: The case of buried low-velocity layers
    • Authors: Daniela Farrugia; Pauline Galea; Sebastiano D’Amico; Enrico Paolucci
      Pages: 196 - 205
      Abstract: Publication date: September 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 100
      Author(s): Daniela Farrugia, Pauline Galea, Sebastiano D’Amico, Enrico Paolucci
      Seismic site response analysis is an important procedure used to obtain parameters such as peak ground motion values. These are needed by the engineering community for reliable seismic design, analysis and retrofitting of structures. One of the inputs for such analysis is the shear-wave velocity profile (V S) of the site. Surface wave methods are increasingly being used to obtain these profiles. However, these are characterised by uncertainties related to the measurements and the model used for interpretation (e.g. the inadequacy of 1D assumption). Moreover, the inversion procedure is also highly non-unique because numerous profiles are able to fit the experimental dispersion curve/s. Even though the uncertainties are not commonly included in site response analysis, their propagation from the dispersion curves to the inversion procedure can lead to significant differences in the site response analysis results. In a previous study, V S profiles were obtained at 20 sites on the Maltese islands (Central Mediterranean) using the Horizontal-to-Vertical Spectral Ratio (H/V), the Extended Spatial Auto-Correlation (ESAC) technique and the Genetic Algorithm. The geology of all the sites is characterised by a layer of clay, which can be up to 75m thick, buried under the Upper Coralline Limestone, a fossiliferous coarse grained limestone. The effect of a thick buried low V S layer, which gives rise to a velocity inversion, in ground response is not well understood and/or documented. The above concerns raised the need for carrying out tests with the aim of better clarifying and understanding which parameters have the most influence on site response analysis and to assess the consequences of inversion non-uniqueness on ground motion amplification and response. From the first part of the study, it was observed that the thickness of the clay layer has the greatest effect on the ground response results. By obtaining ground motion parameters from equivalent profiles, the consequences of the uncertainty in the inversion process, which can be serious at times, are revealed.

      PubDate: 2017-06-12T11:48:31Z
      DOI: 10.1016/j.soildyn.2017.05.033
      Issue No: Vol. 100 (2017)
       
  • A new method for mapping liquefaction-induced lateral spread level
    • Authors: Chengcheng Li; Xiaoming Yuan
      Pages: 206 - 223
      Abstract: Publication date: September 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 100
      Author(s): Chengcheng Li, Xiaoming Yuan
      To meet the objective requirements of civil engineering construction and mitigation of earthquake disasters, and achieve the goal of economic rationality, we propose a new method for liquefaction-induced lateral spread zonation that is adapted to regionalization and modern technology. To overcome the disadvantage of the National Earthquake Hazard Reduction Program (NEHRP) method that depends on high-density boreholes to complete zoning work, two key technologies of the new method are proposed in this paper, including liquefaction lateral spread level (LLSL) criteria and an extraction technique of polygon features to match the LLSL criteria, detailed as follows. (1) LLSL criteria are used to directly determine the lateral spread level within a certain range of each influence factor. (2) The extraction of polygon features for the influence factors. The geologic and soil condition factors are extracted by combining 3-D geographic information systems and a mining visualization system with geologic interpretation and fewer boreholes. The proposed method is used for the liquefaction-induced lateral spread distribution of a 7.8-magnitude earthquake south of Tangshan, China in 1976. The result is consistent with measurements just after that earthquake. This proves that the new method for liquefaction-induced lateral spread zonation is basically reasonable and feasible. The disadvantage of the NEHRP method, which depends on high-density boreholes, is thereby overcome. This can effectively cut economic costs and still keep the necessary accuracy in the sense of regionalization.

      PubDate: 2017-06-12T11:48:31Z
      DOI: 10.1016/j.soildyn.2017.05.030
      Issue No: Vol. 100 (2017)
       
  • Dynamic properties of polypropylene fibre-reinforced silica quarry sand
    • Authors: Haiwen Li; Kostas Senetakis
      Pages: 224 - 232
      Abstract: Publication date: September 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 100
      Author(s): Haiwen Li, Kostas Senetakis
      The study reports on the dynamic behavior of fibre-reinforced sand with a focus on the shear modulus at very small strains. A set of twenty four specimens composed of a silica quarry sand reinforced with different percentages of polypropylene fibres was constructed in the laboratory using two different resonant columns embedded with bender element inserts. One resonant column is of the fixed-free type and the second apparatus is of the fixed-partly fixed type. The percentages of fibre ranged from 0% to 2% and the specimens were tested in a fully saturated state following an isotropic stress path. The shear modulus of the specimens obtained from the bender element tests was computed based on the measured shear wave velocities considering an equivalent density instead of the bulk density. This is because the bender element test method corresponds to a high-frequency technique and adjustment of soil density should take place to account for the relative movement between the solid skeleton and the water that fills the pores. This adjustment provided a better comparison between the obtained moduli from resonant column and bender element tests. Based on the set of experiments, it was found that the small strain shear modulus of the specimens reduced with an increase of the fibre content, which trend was more pronounced for fibre contents greater than 0.5%. The use of a granular void ratio in typical power-law type formulae for the expression of soil modulus could not work effectively, as for example it happens in granular binary mixtures. Based on the experiments, a formula was developed that correlates stiffness to pressure. In this regard, an additional set of dynamic tests was conducted including twenty newly created specimens in order to further validate the new expression, which is more applicable for a well-graded quarry sand as physical portion and for contents of polypropylene fibre from 0% to 2%.

      PubDate: 2017-06-12T11:48:31Z
      DOI: 10.1016/j.soildyn.2017.05.035
      Issue No: Vol. 100 (2017)
       
  • Influence of pore water in the seabed on dynamic response of offshore wind
           turbines on monopiles
    • Authors: M. Bayat; L.V. Andersen; L.B. Ibsen; J. Clausen
      Pages: 233 - 248
      Abstract: Publication date: September 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 100
      Author(s): M. Bayat, L.V. Andersen, L.B. Ibsen, J. Clausen
      The well-known p - y curve method provides soil-structure interaction that does not account for the pore pressure effect for dynamic analysis of offshore wind turbines (OWTs). In order to avoid overly conservative designs, reliable estimates of the dynamic response should be taken into account. The turbine is introduced using a simplified model to assess the eigenfrequencies and modal damping, accounting for pore water flow and excess pore pressure around the monopile. Thus the effect of pore pressure and load frequency are illustrated by implementing a poroelastic model to present more realistic dynamic properties and compare them with results obtained by the p - y curve method. A cyclic loading is considered and the soil stiffness based on the Winkler and Kelvin models is calculated and compared while the soil damping for the Kelvin model is computed. Developed finite element programs are employed to present the results for a two-phase system consisting of a solid skeleton and pore fluid, based on the u - P formulation. Here, u is grain displacement and P is pore water pressure. The developed codes have been validated with commercial software and are implemented to perform free vibration tests to evaluate the eigenfrequencies. A linear poroelastic material model is utilized. An equivalent masses-dashpots-springs system at the pile-cap level is calculated and compared by using Winkler and Kelvin models to highlight the effect of pore pressure and load seepage damping.

      PubDate: 2017-06-12T11:48:31Z
      DOI: 10.1016/j.soildyn.2017.06.001
      Issue No: Vol. 100 (2017)
       
  • Laboratory tests for permeability of sand during liquefaction
    • Authors: Tzou-Shin Ueng; Zih-Fang Wang; Min-Chien Chu; Louis Ge
      Pages: 249 - 256
      Abstract: Publication date: September 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 100
      Author(s): Tzou-Shin Ueng, Zih-Fang Wang, Min-Chien Chu, Louis Ge
      The permeability is a very important property affecting drainage, pore pressure buildup and dissipation, and ground settlement for saturated sand during and after seismically induced liquefaction. A laboratory experiment was developed to conduct tests for evaluating the water movements and permeability in a sand column before, during and after liquefaction. The excess pore water pressures at various depths within the sand specimen, hydraulic gradients, and water flow rates were recorded continuously throughout the tests. The permeability of the sand specimen during the process of liquefaction was calculated from these measurements. Results showed that the permeability of fine Vietnam sand during liquefaction was about 4–5 times the initial value before liquefaction, while it reduced to 0.9–0.97 times the initial value after complete dissipation of the excess pore pressures depending on the density of sand. The permeability of sand during excess pore pressure dissipation after liquefaction was also evaluated.

      PubDate: 2017-06-16T12:09:52Z
      DOI: 10.1016/j.soildyn.2017.05.037
      Issue No: Vol. 100 (2017)
       
  • Optimal design of nonlinear viscous dampers for frame structures
    • Authors: Enrico Parcianello; Corrado Chisari; Claudio Amadio
      Pages: 257 - 260
      Abstract: Publication date: September 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 100
      Author(s): Enrico Parcianello, Corrado Chisari, Claudio Amadio
      It is well-known that in order to decrease displacements and accelerations in a frame structure during earthquakes, purely viscous dampers can be effectively employed, allowing for a remarkable dissipation of seismic input energy. The design of such devices, however, is still an open issue, since it is often carried out by means of inefficient trial-and-error procedures, or simplified analytical approaches which do not guarantee the optimal exploitation of the dampers. This work investigates the use of an optimisation-based approach for the design of nonlinear purely viscous dampers, aimed at improving the seismic behaviour of frame structures. The potential and the flexibility of the method are shown through an illustrative example displaying how different structural requirements (limitation or minimisation of inter-storey drifts and/or forces transferred by the devices) can be easily taken into account by means of a suitable formulation of a constrained optimisation problem.

      PubDate: 2017-06-16T12:09:52Z
      DOI: 10.1016/j.soildyn.2017.06.006
      Issue No: Vol. 100 (2017)
       
  • Dynamic response and failure mechanism of Brazilian disk specimens at high
           strain rate
    • Authors: Mehrdad Imani; Hamid Reza Nejati; Kamran Goshtasbi
      Pages: 261 - 269
      Abstract: Publication date: September 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 100
      Author(s): Mehrdad Imani, Hamid Reza Nejati, Kamran Goshtasbi
      The effect of strain rate on the failure mechanism of rocks is one of the most important aspects in the field of rock dynamics and has been considered in many research works due to its extensive application. This study focuses on dynamic features and failure mechanism of Brazilian disk specimens under high-rate loading. For this purpose, particle flow code 2-dimensional (PFC2D) was used for simulation of Brazilian disk samples. The numerical models were validated by comparing with results of uniaxial compression, Brazilian and Split-Hopkinson Pressure Bar (SHPB) laboratory tests and it is demonstrated that the result of numerical modeling has a good agreement with those of the experimental measurements. The validated numerical model was used for further study of the mechanical behavior of rock specimen at high strain rate. The results of numerical models revealed that there are three different of failure modes for Brazilian disk specimens at different strain rate: (1) tensile splitting failure mode for specimen at strain rate smaller than 150 (1/s), (2) branching failure mode when strain rate varies in range of 150–600 (1/s) and (3) crushing failure mode when the strain rate increases to more than 600 (1/s).

      PubDate: 2017-06-16T12:09:52Z
      DOI: 10.1016/j.soildyn.2017.06.007
      Issue No: Vol. 100 (2017)
       
  • Scenario based seismic re-qualification of caisson supported major bridges
           – A case study of Saraighat Bridge
    • Authors: Pradeep Kumar Dammala; Subhamoy Bhattacharya; Adapa Murali Krishna; Shiv Shankar Kumar; Kaustubh Dasgupta
      Pages: 270 - 275
      Abstract: Publication date: September 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 100
      Author(s): Pradeep Kumar Dammala, Subhamoy Bhattacharya, Adapa Murali Krishna, Shiv Shankar Kumar, Kaustubh Dasgupta
      Many major river bridges were constructed in highly active seismic areas of India much before the seismic code development. Bridges are lifelines infrastructure and as a result, it is necessary to requalify/reasses these structures in the light of the new and improved understanding of seismic resistant design philosophies. The aim of the paper is to develop a simplified methodology to carry out scenario based seismic requalification of major river bridges supported on caisson foundations (also known as Well Foundation). An example problem of Saraighat Bridge located in highly active Himalayan seismic zone is considered to demonstrate the application of the methodology. Field investigation and advanced laboratory tests on soil samples from the bridge site were carried out. The test results reveal that the soil is susceptible to liquefaction and as a result, soil structure interaction analyses are carried out. It is shown that good performance of these type of bridges depend on the displacement response of the pier head so as not to cause unseating of the decks. It is concluded, owing to the large stiffness of the foundations, bridges supported on caisson foundations may not be adversely affected by liquefaction induced effects.

      PubDate: 2017-06-22T16:17:39Z
      DOI: 10.1016/j.soildyn.2017.06.005
      Issue No: Vol. 100 (2017)
       
  • Evaluation of seismic passive earth pressure of inclined rigid retaining
           wall considering soil arching effect
    • Authors: Anindya Pain; Qingsheng Chen; Sanjay Nimbalkar; Yitao Zhou
      Pages: 286 - 295
      Abstract: Publication date: September 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 100
      Author(s): Anindya Pain, Qingsheng Chen, Sanjay Nimbalkar, Yitao Zhou
      Evaluation of seismic passive earth pressure is an important topic of research in geotechnical engineering. In this study seismic passive pressure on an inclined rigid retaining wall supporting horizontal cohesionless backfill is estimated considering arching effect. A planar failure surface is considered in the present analysis. Seismic forces are considered to be pseudo-static in nature. The effect of different parameters on the seismic passive earth pressure is studied in details. The normal stress distribution along the depth of the backfill is found to be nonlinear in nature. Friction angle between wall and the backfill soil has the most significant effect on the distribution of normal stress along the depth of the backfill. The point of application of seismic passive pressure shifts gradually downward for higher seismic forces. Present method is validated with the experimental results available in the literature for static conditions. Comparison of present method with other theories is also presented showing the merit of the present study. Arching effect in the backfill should be considered for high values of wall inclination angle as the present seismic passive resistance is found to be the lowest as compared to other theoretical solutions.

      PubDate: 2017-06-22T16:17:39Z
      DOI: 10.1016/j.soildyn.2017.06.011
      Issue No: Vol. 100 (2017)
       
  • Structure-soil-structure interaction effects on structures retrofitted
           with tuned mass dampers
    • Authors: R.N. Jabary; S.P.G. Madabhushi
      Pages: 301 - 315
      Abstract: Publication date: September 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 100
      Author(s): R.N. Jabary, S.P.G. Madabhushi
      This paper investigates the dynamic structure-soil-structure interaction (SSSI) between two adjacent sway frames, replicating closely spaced residential buildings in an urban setting subjected to seismic input motions. The structures are considered with and without external damping mechanisms by means of tuned mass damper (TMD) configurations. Geotechnical centrifuge tests were conducted to address the current lack of experimental case studies into SSSI and uniquely explore the influences from the presence of TMDs and variations in their configurations on SSSI. SSSI was found to significantly alter the response of proximally located urban structures, as was evident from significantly larger rocking amplitudes and changes in frequency response spectra. TMD effects under SSSI were mostly found to amplify an adjacent structure's peak roof acceleration response and inter-storey drift – this was most aggravated when the damper was de-tuned. TMD effects were found to be relatively more pronounced under smaller earthquakes and could certainly cause occupational inconvenience or even damage in adjacent buildings.

      PubDate: 2017-06-22T16:17:39Z
      DOI: 10.1016/j.soildyn.2017.05.017
      Issue No: Vol. 100 (2017)
       
  • Shaking table tests and numerical studies on the effect of viscous dampers
           on an isolated RC building by friction pendulum bearings
    • Authors: Ying Zhou; Peng Chen
      Pages: 330 - 344
      Abstract: Publication date: September 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 100
      Author(s): Ying Zhou, Peng Chen
      Base isolation is an effective way for diminishing the response of a structure to seismic action. However, this results in large displacements for isolators, particularly for buildings located in near-fault sites. Viscous dampers (VDs) are often used as supplementary devices to reduce those displacements, but there is a potential for significant increases in story drift and floor acceleration of the superstructure. This paper aims to investigate the effect of viscous dampers on a base-isolated 16-storey reinforced concrete (RC) framed structure with friction pendulum bearings (FPBs) through shaking table tests and numerical simulations. First, the similitude design method for small scaled test models was introduced, including the stiffness-based method for FPBs and the energy-based method for VDs. Then a shaking table test for the isolated structure using FPBs was conducted. Experimental and numerical results were utilized to investigate the effect of VDs on both the displacement of the isolators and the response of the superstructure. It is concluded that VDs do not significantly influence either the isolation displacements or the structural response in a small earthquake, but isolator displacements can be remarkably controlled in a strong earthquake at the expense of a slight increase in the superstructure response.

      PubDate: 2017-07-02T16:32:37Z
      DOI: 10.1016/j.soildyn.2017.06.002
      Issue No: Vol. 100 (2017)
       
  • Amplification of strong ground motions at Heathcote Valley during the
           2010–2011 Canterbury earthquakes: Observation and 1D site response
           analysis
    • Authors: Seokho Jeong; Brendon A. Bradley
      Pages: 345 - 356
      Abstract: Publication date: September 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 100
      Author(s): Seokho Jeong, Brendon A. Bradley
      The strong motion station at Heathcote Valley School (HVSC) recorded intense ground accelerations (peak value of 1.4g in horizontal and 2.2g in vertical component) during the 22 February 2011 Christchurch earthquake. More importantly, ground motions recorded at HVSC in numerous other events during the 2010–2011 Canterbury earthquake sequence also exhibited consistently larger peak ground accelerations compared with nearby strong motion stations, which suggests significant near-surface site amplification effects. This paper presents a quantitative case study of near-surface site effects of Heathcote Valley during the 2010–2011 Canterbury earthquake sequence, by means of one-dimensional nonlinear dynamic finite element analyses based on the recorded ground motions and a rigorous site characterisation study. Various geophysical and geotechnical in-situ tests are performed to establish a simplified three-dimensional representation of wave velocities, mass densities and the geological structure (i.e. layering) of Heathcote Valley. Simulations are performed using the velocity profile at the location of station HVSC with the finite element analysis program OpenSees. Overall, simulations agree well with the recorded motions and suggest that ground motions at HVSC are amplified in a wide band of frequencies. However, the one-dimensional simulations tend to underestimate the site response at frequencies higher than the site fundamental frequency, likely due to its inability of modelling surface waves caused by the inclined soil-rock interface. Comparison between the nonlinear and the equivalent linear model shows that, although both approaches produce similar level of peak amplitude, the equivalent linear model significantly underestimates the high frequency motions.

      PubDate: 2017-07-02T16:32:37Z
      DOI: 10.1016/j.soildyn.2017.06.004
      Issue No: Vol. 100 (2017)
       
  • Dynamic soil properties for seismic ground response studies in
           Northeastern India
    • Authors: Pradeep Kumar Dammala; Adapa Murali Krishna; Subhamoy Bhattacharya; George Nikitas; Mehdi Rouholamin
      Pages: 357 - 370
      Abstract: Publication date: September 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 100
      Author(s): Pradeep Kumar Dammala, Adapa Murali Krishna, Subhamoy Bhattacharya, George Nikitas, Mehdi Rouholamin
      Stiffness and damping properties of soil are essential parameters for any dynamic soil structure interaction analysis. Often the required stiffness and damping properties are obtained from the empirical curves. This paper presents the stiffness and damping properties of two naturally occurring sandy soils collected from a river bed in a highly active seismic zone in the Himalayan belt. A series of resonant column tests are performed on the soil specimens with relative densities representative of the field and with varying confining pressures. The test results are compared with the available empirical curves. Furthermore, a ground response analysis study is also carried out for a bridge site in the region using both the empirical curves and experimentally obtained curves. It has been observed that the application of empirical modulus and damping curves in ground response prediction often leads to underestimation of the seismic demands on the structures. The established soil curves can thus be utilized in performing seismic ground response studies for the design of new structures or requalification/reassessment of existing structures in the northeastern part of India.

      PubDate: 2017-07-02T16:32:37Z
      DOI: 10.1016/j.soildyn.2017.06.003
      Issue No: Vol. 100 (2017)
       
  • Small-strain shear modulus of calcareous sand and its dependence on
           particle characteristics and gradation
    • Authors: Pham Huu Ha Giang; Peter O. Van Impe; William F. Van Impe; Patrick Menge; Wim Haegeman
      Pages: 371 - 379
      Abstract: Publication date: September 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 100
      Author(s): Pham Huu Ha Giang, Peter O. Van Impe, William F. Van Impe, Patrick Menge, Wim Haegeman
      The soil small-strain shear modulus, G0, is necessary for static and dynamic soil analyses and is often correlated to other soil properties such as density and void ratio, on their turn depending on gradation. The paper first presents a concise literature review of parameters influencing G0 in detail. Secondly, a particle shape analysis is performed. Silica sand is found much more spherical than calcareous sand, and calcareous sand becomes more spherical after crushing. Bender element test results indicate that not only uniformity coefficient (Cu) but also particle characteristics including particle shape and stiffness are very important to G0. G0 of calcareous sand is found higher than that of silica sand. Indeed, with less sphericity and more angularity, the variety of particle shape in calcareous sand produces a better fabric for shear wave propagation. For calcareous sand, the test results show that particle shape is the main factor affecting G0. Less dynamic stiffness is found for particles owning more sphericity and less angularity. The increase of Cu or finer particles (at low Cu) causes a decrease in G0. Finally, predictions of G0 for the tested calcareous sands using empirical equations from previous studies give very high relative errors (16.7–30%).

      PubDate: 2017-07-02T16:32:37Z
      DOI: 10.1016/j.soildyn.2017.06.016
      Issue No: Vol. 100 (2017)
       
  • Vector-valued intensity measures for incremental dynamic analysis
    • Authors: Ying Zhou; Pinglan Ge; Jianping Han; Zheng Lu
      Pages: 380 - 388
      Abstract: Publication date: September 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 100
      Author(s): Ying Zhou, Pinglan Ge, Jianping Han, Zheng Lu
      In incremental dynamic analysis (IDA), use of an efficient intensity measure (IM) is of vital importance. Efficiency means good explanatory power of the IM in regard to specific engineering demand parameter (EDP) that can help reduce the number of records used to estimate response of structures under given accuracy. According to dimension of the parameters, intensity measures can be classified into scalar-valued IMs and vector-valued IMs. While scalar-valued IMs have been studied systematically, vector-valued IMs have not been investigated comprehensively. Besides, vector-valued IMs considering the effect of higher modes have not been proposed. Hence in order to provide a systematic investigation on vector-valued IMs, this paper proposes five vector-valued IMs with two considering higher mode effect and three incorporating period elongation effect. Then a low-rise and a middle-rise reinforced concrete frames are modeled and analysed by PERFORM-3D and IDA under fifteen suites ground motion records for each structure. To evaluate efficiency of the proposed IMs, residual sum of squares (RSS) and R 2 were calculated by logistic regression of IDA data. Results verified the better efficiency of vector-valued IMs than scalar-valued IMs. It is also proved that the relationship between IM and EDP can be expressed as a linear regression of logarithm for both scalar-valued IMs and vector-valued IMs. It turns out that a desirable IM should be selected based on the features of the specific structure. For structures dominated by the first mode, the impact of nonlinearity is of vital importance and should be mainly considered when choosing desirable IMs. Furthermore, for IMs considering nonlinearity effect, efficiency is relevant to the number of spectral acceleration incorporated; for IMs incorporating higher mode effect, the proposed multi-valued IM is more efficient than the two-valued type.

      PubDate: 2017-07-02T16:32:37Z
      DOI: 10.1016/j.soildyn.2017.06.014
      Issue No: Vol. 100 (2017)
       
  • Focusing of ground vibrations generated by high-speed trains travelling at
           trans-Rayleigh speeds
    • Authors: Victor V. Krylov
      Pages: 389 - 395
      Abstract: Publication date: September 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 100
      Author(s): Victor V. Krylov
      In the present paper, the effects of focusing of ground vibrations generated by high speed trains travelling at trans-Rayleigh speeds, i.e. under the condition of ground vibration boom, are considered theoretically. These effects are similar to the effects of focusing of sound waves radiated by supersonic aircraft. In particular, if a railway track has a bend, e.g. to provide the possibility of changing direction of train movement, the Rayleigh surface waves generated by high-speed trains under the condition of ground vibration boom may become focused. This results in concentration of their energy along a simple caustic line at one side of the track and in the corresponding increase in ground vibration amplitudes. The effect of focusing of Rayleigh waves may occur also if a train moves along a straight line with acceleration a and its current speed v(t) is higher than Rayleigh wave velocity in the ground. In the present paper, both the above-mentioned focusing mechanisms are investigated in detail using the Green's function formalism and the expressions for space-time distributions of track-train-induced dynamic forces that take into account either track curvature or train acceleration. It is shown that in both these cases the effect of focusing can result in noticeable increase in generated ground vibrations. The obtained results are illustrated by numerical calculations.

      PubDate: 2017-07-02T16:32:37Z
      DOI: 10.1016/j.soildyn.2017.06.015
      Issue No: Vol. 100 (2017)
       
  • Seismic performance of strip foundations on liquefiable soils with a
           permeable crust
    • Authors: V.E. Dimitriadi; G.D. Bouckovalas; A.G. Papadimitriou
      Pages: 396 - 409
      Abstract: Publication date: September 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 100
      Author(s): V.E. Dimitriadi, G.D. Bouckovalas, A.G. Papadimitriou
      Modern seismic codes dictate that the use of shallow foundations on liquefiable soils may be considered only after appropriate ground improvement. No further instructions are given regarding the improvement depth, or what changes if the surface layer (crust) does not liquefy. Hence, it is standard practice to improve the entire liquefiable soil layer below the foundation, whatever its depth or thickness. This study examines the seismic performance of strip foundations laying on a two-layered soil profile, consisting of a bottom layer of liquefiable sand and a (manmade or natural) permeable crust on top. Regardless of its origin, this crust does not develop (significant) excess pore pressures during shaking and is stronger and stiffer than the underlying liquefied sand. The problem is investigated numerically, through fully coupled non-linear dynamic finite-difference analyses. Following the identification of the governing response parameters, a set of multi-variable relations is developed for the approximate assessment of the seismic footing settlements and the bearing capacity degradation due to liquefaction appearing below the permeable crust.

      PubDate: 2017-07-02T16:32:37Z
      DOI: 10.1016/j.soildyn.2017.04.021
      Issue No: Vol. 100 (2017)
       
  • Experimental study of a segmented metro tunnel in a ground fissure area
    • Authors: Nina Liu; Qiangbing Huang; Yujie Ma; Rifat Bulut; Jianbing Peng; Wen Fan; Yuming Men
      Pages: 410 - 416
      Abstract: Publication date: September 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 100
      Author(s): Nina Liu, Qiangbing Huang, Yujie Ma, Rifat Bulut, Jianbing Peng, Wen Fan, Yuming Men
      This paper studies the seismic response of a segmented metro tunnel with flexible joints passing through active ground fissures in Xi’an by shaking table model test. A coupling dynamic ground motion was generated in the test model. The tunnel acceleration, earth pressure and tunnel structure strain were monitored and compared. It was observed that each part of the tunnel has an independent movement with flexible joints. The tunnel located in the hanging wall has 3.17 times peak acceleration than that in the foot wall. Higher magnitudes of earth pressures were recorded close to the areas of the ground fissures. The earth pressure in the hanging wall was greater than that in the foot wall. The coupling loads increase the earth pressure. The strain in the middle of the tunnel arch was the largest. The strain at the bottom of the floor was the secondary. The one on the top of the arch was the smallest. The strain increased less in each section because the tunnel is divided into four parts by flexible joints, and no sharp strain increase close to the ground fissure was observed. The results indicate that the flexible joints can decrease the stress concentration. The tunnel with flexible joints can adjust to large deformations in the ground fissure areas.

      PubDate: 2017-07-02T16:32:37Z
      DOI: 10.1016/j.soildyn.2017.06.018
      Issue No: Vol. 100 (2017)
       
  • NEEWS: A novel earthquake early warning model using neural dynamic
           classification and neural dynamic optimization
    • Authors: Mohammad Hossein Rafiei; Hojjat Adeli
      Pages: 417 - 427
      Abstract: Publication date: September 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 100
      Author(s): Mohammad Hossein Rafiei, Hojjat Adeli
      An Earthquake Early Warning System (EEWS) can save lives. It can also be used to manage the critical lifeline infrastructure and essential facilities. Recent research on earthquake prediction towards the development of an EEWS can be classified into two groups based on a) arrival of P waves and b) seismicity indicators. The first approach can provide warnings within a timeframe of seconds. A seismicity indicator-based EEWS is intended to forecast major earthquakes within a time frame of weeks. In this paper, a novel seismicity indicator-based EEWS model, called neural EEWS (NEEWS), is presented for forecasting the earthquake magnitude and its location weeks before occurrence using a combination of a classification algorithm (CA) based on machine learning concepts and a mathematical optimization algorithm (OA). The role of the CA is to find whether there is an earthquake in a given time period greater than a predefined magnitude threshold and the role of the OA is to find the location of that earthquake with the maximum probability of occurrence. The model is tested using earthquake data in southern California with a combination of four CAs and one OA to find the best EEWS model. The proposed model is capable of predicting strong disastrous events as long as sufficient data are available for such events. The paper provides a novel solution to the complex problem of earthquake prediction through adroit integration of a machine learning classification algorithm and the robust neural dynamics optimization algorithm of Adeli and Park.

      PubDate: 2017-07-12T02:55:26Z
      DOI: 10.1016/j.soildyn.2017.05.013
      Issue No: Vol. 100 (2017)
       
  • Seismic hazard assessment for Harrat Lunayyir – A lava field in
           western Saudi Arabia
    • Authors: Hani Mahmoud Zahran; Sherif Mohamed El-Hady
      Pages: 428 - 444
      Abstract: Publication date: September 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 100
      Author(s): Hani Mahmoud Zahran, Sherif Mohamed El-Hady
      Distribution of earthquakes along the western part of the Arabian Peninsula is related to the Red Sea floor spreading and volcanism. The Arabian Peninsula contains Cenozoic lava fields (harrats) extending from Yemen in the south up to Syria in the north. Harrat Lunayyir that is a very young volcanic area has suffered from two earthquake swarms with maximum magnitude MW 5.7 caused by the dike intrusion. The area was not considered as a seismic source zone when constructing seismic hazard maps used in the current issue of Saudi Building Code (SBC-2007). In this work, probabilistic seismic hazard is estimated for the Harrat Lunayyir area and the town of Alays located a few kilometers to south-east of the Harrat. Two models of seismic source zones describing seismic process in Harrat Lunayyir are considered as alternatives in the logic tree scheme, namely: the areal source model and the fault (characteristic earthquake) source model. The results of probabilistic estimations of seismic hazard show that the area is characterized by significant level of hazard. The expected peak ground amplitudes at rock site and for return period 2475 yrs are larger than 200cm/s2 and 140cm/s2 for the central part of the area and the town of Alays respectively. The level of uncertainty quantified in terms of “relative uncertainty” is the largest in the central part of the area.

      PubDate: 2017-07-12T02:55:26Z
      DOI: 10.1016/j.soildyn.2017.06.009
      Issue No: Vol. 100 (2017)
       
  • Water and wastewater steel tanks under multiple earthquakes
    • Authors: Fotini D. Konstandakopoulou; George D. Hatzigeorgiou
      Pages: 445 - 453
      Abstract: Publication date: September 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 100
      Author(s): Fotini D. Konstandakopoulou, George D. Hatzigeorgiou
      This study focuses on the inelastic response of water and wastewater steel tanks under multiple earthquakes. The main innovation of the proposed study has to do with the quantification of the seismic sequence effect into steel tanks, a phenomenon which has not been studied in the past. Firstly, this paper considers real seismic sequences that have been recorded during a short period of time (up to three days), by the same station, in the same direction, and almost at the same fault distance. In these cases, due to lack of time, any rehabilitation action is difficult or impractical and the multiplicity of earthquakes can lead to important damage accumulation. Furthermore, artificial seismic sequences are also examined where they have been generated by a rational and random combination of real single events. It is found that due to the multiple earthquakes effect, it seems to be unreliable to consider only single earthquake records in steel tank design process, since this long-established assumption leads to underestimated demands in terms of bearing capacity and deformation.

      PubDate: 2017-07-12T02:55:26Z
      DOI: 10.1016/j.soildyn.2017.06.026
      Issue No: Vol. 100 (2017)
       
  • Seismic design of bilinear geosynthetic-reinforced slopes
    • Authors: Xiaobo Ruan; Xin Guo; Yu-Shan Luo; Shulin Sun
      Pages: 454 - 457
      Abstract: Publication date: September 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 100
      Author(s): Xiaobo Ruan, Xin Guo, Yu-Shan Luo, Shulin Sun
      The scenario of two tiered geosynthetic-reinforced slopes, where the upper tier is vertical and the lower tier is inclined at an angle, is termed as a bilinear geosynthetic-reinforced slope (BGRS) in this note. This note presents a pseudo-static limit equilibrium approach employing a top-down log spiral mechanism to determine the resultant reinforcement force in the lower tier required for global seismic stability. An example was presented to illustrate steps for achieving the resultant reinforcement force required for internal seismic design of reinforcement rupture and show how much the maximum reinforcement force at each layer is in line with its distribution function. The reinforcement force in the BGRS is subsequently compared with that in the equivalent geosynthetic-reinforced slope under different case. In addition, it is found that the resultant reinforcement force in the lower tier increases first and then decreases with an increase of height ratio of the upper tier to the BGRS.

      PubDate: 2017-07-12T02:55:26Z
      DOI: 10.1016/j.soildyn.2017.06.020
      Issue No: Vol. 100 (2017)
       
  • Stochastic seismic response and dynamic reliability analysis of slopes: A
           review
    • Authors: Min Xiong; Yu Huang
      Pages: 458 - 464
      Abstract: Publication date: September 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 100
      Author(s): Min Xiong, Yu Huang
      This study analyzes the factors that influence the seismic stability of slopes and summarizes the variability and uncertainties in the various components. It also shows why the variability should be considered in stability analyses of slopes. Furthermore, stochastic seismic performance evaluations corresponding to the different sources of variability are summarized and reviewed. In particular, new random vibration methods are applied to seismic response studies. Finally, by characterizing the intrinsic factors and understanding the variability in dynamic slope systems, future development of the stochastic seismic response analysis method is elaborated.

      PubDate: 2017-07-12T02:55:26Z
      DOI: 10.1016/j.soildyn.2017.06.017
      Issue No: Vol. 100 (2017)
       
  • Multi-scale physical model of shield tunnels applied in shaking table test
    • Authors: Zhen Bao; Yong Yuan; Haitao Yu
      Pages: 465 - 479
      Abstract: Publication date: September 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 100
      Author(s): Zhen Bao, Yong Yuan, Haitao Yu
      Experimental simulation of long-distance shield tunnels is difficult due to the enormous volumes of segments and complexity of joints. In this paper, a multi-scale method is proposed to simulate the test model of shield tunnels, which discretizes the entire model structure into the segmental equivalent ring portion (SER) and the equivalent uniform tube portion (EUT). The EUT model is employed to capture seismic response characteristics of the entire tunnel system, whereas the SER model is employed to describe in detail the deformation responses in lining segments and joints at positions of potential damage or interest. The proposed multi-scale physical model for shield tunnels is validated through shaking table tests, in which a full refined model is set as benchmark for comparison. Results show that: 1) the multi-scale physical model demonstrates the same macroscopic dynamic response, such as acceleration responses of model linings, as the full refined model; and 2) dynamic responses such as the extension of joints in the central zone of SER portion of the multi-scale model is consistent with those in the full refined model. The proposed multi-scale method provides an effective way for the design of complex segmental tunnel models applied in shaking table tests.

      PubDate: 2017-07-12T02:55:26Z
      DOI: 10.1016/j.soildyn.2017.06.021
      Issue No: Vol. 100 (2017)
       
  • Seismic analysis of nailed soil slope considering interface effects
    • Authors: Dhanaji Chavan; Goutam Mondal; Amit Prashant
      Pages: 480 - 491
      Abstract: Publication date: September 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 100
      Author(s): Dhanaji Chavan, Goutam Mondal, Amit Prashant
      Natural soil slopes are often reinforced with nails to stabilize them against earthquake loading. Although pseudo-static method is widely used in designing such slopes; it fails to provide important information such as deformation of slope, effect of soil-nail interface etc. A 2-D finite element model of typical nailed slope has been prepared during this study using OpenSees to perform seismic analysis with due consideration to soil nonlinearity, pressure dependency of soil and separation-sliding at soil-nail interface. It is found that the soil-nail interface modelling can significantly influence the permanent deformation of slope after seismic event. The overburden pressure on the nail varies significantly during the earthquake loading and the variation is more when sliding and separation is allowed at the soil-nail interface. It is also found that the model with fixed interface leads to a perception of reinforced soil acting as a relatively rigid block, which results into an unconservative design from overall deformation perspective.

      PubDate: 2017-07-12T02:55:26Z
      DOI: 10.1016/j.soildyn.2017.06.024
      Issue No: Vol. 100 (2017)
       
  • Influence of residual displacements on the design displacement of
           spherical friction-based isolation systems
    • Authors: D. Cardone; G. Gesualdi
      Pages: 492 - 503
      Abstract: Publication date: September 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 100
      Author(s): D. Cardone, G. Gesualdi
      This paper presents the results of an extensive parametric study aimed at investigating the influence of residual displacements on the design displacement of spherical friction-based isolation systems. Residual displacements may significantly jeopardize the displacement capacity of spherical friction-based isolation systems thus causing extensive damage or even triggering structural collapse. For that reason, they must be properly taken into account in the design. The study builds on the results of thousands of nonlinear response-time history analyses of SDOF systems, using almost one hundred ground motions pairs. Residual displacements arising from both individual earthquakes and sequences of seismic ground motions are considered. Based on regression analysis of results, a closed-form equation is derived to predict residual displacements of spherical friction-based isolation systems as a function of the main parameters governing their mechanical behavior. The proposed relationship is compared with state-of-the-art relationships and current seismic code provisions.

      PubDate: 2017-07-12T02:55:26Z
      DOI: 10.1016/j.soildyn.2017.07.001
      Issue No: Vol. 100 (2017)
       
  • Seismic hazard maps in Macedonia
    • Authors: V.W. Lee; M.D. Trifunac
      Pages: 504 - 517
      Abstract: Publication date: September 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 100
      Author(s): V.W. Lee, M.D. Trifunac
      We present seismic hazard maps for Macedonia and show how the Uniform Hazard Spectra (UHS) method eliminates the difficulties associated with the use of the fixed- shape design spectra. The UHS method also eliminates the issues that result from scaling in terms of peak accelerations—when it is necessary to include hazard contributions from large distant earthquakes—as well as the problem of the inability of the fixed-shape spectra to describe frequency-dependent spectral shapes for different probabilities of exceedance. We also show how far south contributions of the Vrancea earthquakes reach as seen in the UHS of strong ground motion in Macedonia.

      PubDate: 2017-07-12T02:55:26Z
      DOI: 10.1016/j.soildyn.2017.06.010
      Issue No: Vol. 100 (2017)
       
  • Comparison of shear wave velocities evaluated in the core zone of an
           existing fill dam by field and laboratory tests
    • Authors: Ik-Soo
      Abstract: Publication date: September 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 100
      Author(s): Ik-Soo Ha
      The objective of this study is to compare shear wave velocities evaluated by laboratory and field tests in the core zone of an existing fill dam, and to verify the applicability of empirical methods by comparing the shear wave velocities evaluated by empirical methods with those evaluated by experimental methods. In this study, boring and sampling were conducted at the Yeongcheon dam in Korea. Laboratory tests on the core samples were carried out and field tests such as borehole surveys and seismic methods were conducted to evaluate the shear wave velocity. The results obtained by laboratory and field tests were compared. Furthermore, the results obtained by these experimental methods were compared with those obtained by empirical methods. The shear wave velocity determined by the seismic methods was, to a limited extent, lower than that determined by the borehole surveys at shallow depths of less than 15m, but was predicted to be similar at depths deeper than 15m. The results of the two kinds of laboratory tests were almost similar to each other but both the results were 10–20% lower than those obtained by the seismic methods. The results obtained by the empirical method based on the field tests and the measured in-situ records were similar to the field test results. On the other hand, the results obtained by the empirical method using the basic properties of sample cores were similar to the laboratory test results.

      PubDate: 2017-06-22T16:17:39Z
       
  • Three-dimensional shakedown analysis of ballasted railway structures under
           moving surface loads with different load distributions
    • Authors: Yan Zhuang; Kangyu Wang
      Abstract: Publication date: September 2017
      Source:Soil Dynamics and Earthquake Engineering, Volume 100
      Author(s): Yan Zhuang, Kangyu Wang
      Shakedown of ballasted railway structures was analyzed based on Melan's shakedown theorem, in which the wheel/rail contact was approximated by Hertz (circular and elliptical contact areas), uniform and trapezoidal load distributions, separately. The shakedown solutions incorporating to the three-dimensional finite element model calculated shakedown multiplier by means of a self-equilibrated critical residual stress field. The shakedown multiplier for multi-layered ballasted railway structure was determined as the minimum one among all layers. The results showed that elliptical Hertz and uniform load yielded the largest and smallest shakedown limits, respectively, with the maximum difference of approximately 64%. The shakedown limits always occurred at ballast layer for relatively small frictional coefficient, whilst occurred at rail for low rail's yield stress with large frictional coefficient. As expected, the shakedown limits decreased as the ballast stiffness and thickness increased, especially for relatively small frictional coefficient; while increased with raising rail's yield stress. The material properties and thickness should therefore be optimally designed so as to provide a maximum resistance to the structure failure and reduce the material costs.

      PubDate: 2017-06-22T16:17:39Z
       
 
 
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