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Journal Cover Soil Dynamics and Earthquake Engineering
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   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0267-7261
   Published by Elsevier Homepage  [3039 journals]
  • Editorial Board / Aims and Scope
    • Abstract: Publication date: October 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 89




      PubDate: 2016-09-22T13:49:00Z
       
  • Fatigue cracking failure criterion for flexible pavements under moving
           vehicles
    • Abstract: Publication date: November 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 90
      Author(s): Niki D. Beskou, Stephanos V. Tsinopoulos, George D. Hatzigeorgiou
      An improved fatigue cracking criterion for flexible pavements is developed. It relates the allowable number of load repetitions with the maximum tensile strain at the bottom of the asphalt concrete layer that causes cracking there. The criterion is established by combining an empirical relationship providing the number of load repetitions as a function of the layer thicknesses and the axle loading as obtained by the AASHO Road Test with that maximum tensile strain developed at the bottom of the asphaltic layer. Because this maximum tensile strain is computed by a FEM that analyses pavements under moving vehicles and assumes the asphaltic layer to behave as a linear viscoelastic material, the resulting failure criterion takes into account speed and viscoelastic material behavior. Thus, this criterion is an improved version of the existing ones based on static or dynamic loading and linear elastic material behavior.


      PubDate: 2016-09-22T13:49:00Z
       
  • Soil and structure damping from single station measurements
    • Abstract: Publication date: November 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 90
      Author(s): Silvia Castellaro
      In seismology and seismic engineering soils and structures are modeled as oscillators characterized by modal (resonance) frequencies, shapes and damping. In 1973 Cole proposed the RandomDec technique to estimate both the damping and the fundamental mode of structures from the recorded time series at a single point, with no need for spectral analyses. Here we propose a number of modifications to the original RandomDec approach, that we group under the name DECÓ, which allow to determine the damping as a function of the frequency and therefore the damping of all the vibration modes. However, the motion of structures is so amplified at the resonance frequencies that detecting the characteristic parameters by recording ambient vibrations is relatively easy. More interesting is to apply the DECÓ approach to the soil in the attempt to estimate the mode damping from single station measurements. On soils, the resonance frequencies are normally identified as peaks in the horizontal to vertical spectral ratios of microtremors. However, at these frequencies what is observed is a local minimum in the vertical spectral component, sometimes associated to local maxima in the horizontal components, whose visibility depend on the specific amount of SH and Love waves at the site. The determination of soil damping is therefore a much less trivial task on soils than on structures. By using microtremor and earthquake recordings we estimate the soil damping as a function of shear strain and observe that this is one order of magnitude larger than what is measured in the laboratory on small scale samples, at least at low-intermediate strain levels. This has severe consequences on the numerical seismic site response analyses and on soil dynamic modeling.


      PubDate: 2016-09-22T13:49:00Z
       
  • Two-dimensional translation, rocking, and waves in a building during
           soil-structure interaction excited by a plane earthquake P-wave pulse
    • Abstract: Publication date: November 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 90
      Author(s): Vlado Gičev, Mihailo D. Trifunac, Nebojša Orbović
      A two-dimensional model of a building supported by a rectangular, flexible foundation embedded in the soil is analyzed for excitation by an incident plane P-wave. The building, the foundation, and the soil have different material properties. The building is assumed to be anisotropic and linear, while the soil and the foundation are assumed to be isotropic and can experience nonlinear deformations. In general, the work spent for the development of nonlinear strains in the soil can consume a significant part of the input wave energy and thus less energy is available for the excitation of the building. However, in the case of excitation by a plane P-wave pulse, we show that the nonlinear response in the soil and the foundation does not significantly change the nature of excitation in the base of the building. It is noted that the response of a building can be approximated by base translation and rocking for excitation by long, strong motion waves.


      PubDate: 2016-09-22T13:49:00Z
       
  • Liquefaction potential and strain dependent dynamic properties of Kasai
           River sand
    • Abstract: Publication date: November 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 90
      Author(s): Rana Chattaraj, Aniruddha Sengupta
      The availability of efficient numerical techniques and high speed computation facilities for carrying out the nonlinear dynamic analysis of soil-structure interaction problems and the analysis of ground response due to earthquake loading increase the demand for proper estimation of dynamic properties of soil at small strain as well as at large strain levels. Accurate evaluation of strain dependent dynamic properties of soil such as shear modulus and damping characteristics along with the liquefaction potential are the most important criteria for the assessments of geotechnical problems involving dynamic loading. In this paper the results of resonant column tests and undrained cyclic triaxial tests are presented for Kasai River sand. A new correlation for dynamic shear damping (D s ) and maximum dynamic shear modulus (G max ) are proposed for the sand at small strain. The proposed relationships and the observed experimental data match quite well. The proposed relationships are also compared with the published relationships for other sands. The liquefaction potential of the sand is estimated at different relative densities and the damping characteristics at large strain level is also reported. An attempt has been made to correlate the G max with the cyclic strength of the soil and also with the deviator stress (at 1% strain) from static triaxial tests.


      PubDate: 2016-09-22T13:49:00Z
       
  • Relevance of the incidence angle of the seismic waves on the dynamic
           response of arch dams
    • Abstract: Publication date: November 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 90
      Author(s): F. García, J.J. Aznárez, L.A. Padrón, O. Maeso
      This paper aims at studying the influence of the nature and direction of incidence of impinging seismic waves on the dynamic response of arch dams. A model for the seismic excitation is proposed in which the three free-field accelerograms defining the seismic input signal at ground surface are generated by different sets of simultaneous obliquely-incident P and S planar body waves. The dynamic response of the Morrow Point dam under such seismic excitations is studied considering the situation of a full reservoir and the existence of bottom sediments. Such response is computed by means of a multidomain boundary element code that allows the direct dynamic analysis of problems. It is found that, for the cases studied herein, oblique incidence produces seismic responses significantly larger than those observed for vertical incidence, which suggests that analyses considering only vertical incidence could be underestimating the seismic response of this type of structures.


      PubDate: 2016-09-22T13:49:00Z
       
  • Numerical simulation of earthquake-induced liquefactions considering the
           principal stress rotation
    • Abstract: Publication date: November 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 90
      Author(s): Zhe Wang, Yunming Yang, Hai-Sui Yu, Kanthasamy K. Muraleetharan
      Dynamic loadings such as earthquake loadings can generate considerable principal stress rotation (PSR) in the saturated soil. The PSR without changes of principal stress magnitudes can generate additional excess pore water pressures and plastic strains, thus accelerating liquefaction in undrained conditions. This paper simulates a centrifuge model test using the fully coupled finite element method considering the PSR. The impact of PSR under the earthquake loading is taken into account by using an elastoplastic soil model developed on the basis of a kinematic hardening soil model with the bounding surface concept. The soil model considers the PSR by treating the stress rate generating the PSR independently. The capability of this soil model is verified by comparing the numerical predictions and experimental results. It also indicates that the PSR impact can not be ignored in predictions of soil liquefaction.


      PubDate: 2016-09-22T13:49:00Z
       
  • Dynamic inelastic analysis of 3-D flexible pavements under moving
           vehicles: A unified FEM treatment
    • Abstract: Publication date: November 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 90
      Author(s): Niki D. Beskou, George D. Hatzigeorgiou, Dimitrios D. Theodorakopoulos
      The dynamic response of flexible road pavements to moving vehicles is numerically obtained by the time domain finite element method under three-dimensional conditions with the aid of the commercial program ANSYS. The pavement structure is modeled as a system of three layers with the top one (asphalt concrete) exhibiting viscoelastic or viscoplastic and the other two elastic or elastoplastic Drucker-Prager material behavior. The dimensions of the pavement domain, its degree of discretization, its kind of boundaries (rollers everywhere) and the appropriate time step are selected to provide solutions of acceptable accuracy in an efficient manner. Symmetry considerations are also taken into account. The moving with constant speed distributed loads (wheels) of the vehicle are simulated by assigning time dependent load values at all the pavement surface nodes along the vehicle path, which are activated at the time it takes for every load to travel the distance from the origin to every node's location. Comparisons of the dynamic response results in terms of deflections, stresses and strains of the above inelastic models against those corresponding to elastic material behavior under moving or static loads as well as those coming from two field experiments are made and useful practical conclusions are drawn.


      PubDate: 2016-09-22T13:49:00Z
       
  • Seismic response of retaining walls with cohesive backfill: Centrifuge
           model studies
    • Abstract: Publication date: November 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 90
      Author(s): Gabriel Candia, Roozbeh Geraili Mikola, Nicholas Sitar
      Observations from recent earthquakes show that retaining structures with non-liquefiable backfills perform extremely well; in fact, damage or failures related to seismic earth pressures are rare. The seismic response of a 6-m-high braced basement and a 6-m free-standing cantilever wall retaining a compacted low plasticity clay was studied in a series of centrifuge tests. The models were built at a 1/36 scale and instrumented with accelerometers, strain gages and pressure sensors to monitor their response. The experimental data show that the seismic earth pressure on walls increases linearly with the free-field PGA and that the earth pressures increase approximately linearly with depth, where the resultant acts near 0.33H above the footing as opposed to 0.5–0.6H, which is suggested by most current design methods. The current data suggest that traditional limit equilibrium methods yield overly conservative earth pressures in areas with ground accelerations up to 0.4g.


      PubDate: 2016-09-22T13:49:00Z
       
  • Numerical evaluation of the effectiveness of flexible joints in buried
           pipelines subjected to strike-slip fault rupture
    • Abstract: Publication date: November 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 90
      Author(s): Vasileios E. Melissianos, Georgios P. Korakitis, Charis J. Gantes, George D. Bouckovalas
      Buried steel pipelines transport large amounts of fuel over long distances and inevitably cross active tectonic seismic faults when seismic areas are traversed. Eventual fault activation leads to large imposed displacements on the pipeline, which may then fail due to local wall buckling or tensile weld fracture, having grave financial, social and environmental consequences. In this paper, flexible joints are evaluated as an innovative mitigating measure against the consequences of faulting on pipelines. Joints are introduced in the pipeline in the fault vicinity, aiming at absorbing the developing deformation through relative rotation between adjacent pipeline parts, which then remain relatively unstressed. The effectiveness of flexible joints is numerically evaluated through advanced 3D nonlinear finite element modeling. Extensive parametric analysis is carried out to determine the effect of pipeline – fault crossing angle, fault offset magnitude, joint angular capacity, burial depth and diameter over thickness ratio on the joint efficiency. The uncertainty regarding the fault trace is also addressed.


      PubDate: 2016-09-22T13:49:00Z
       
  • A performance-based approach for design of ground densification to
           mitigate liquefaction
    • Abstract: Publication date: November 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 90
      Author(s): Hadi Shahir, Ali Pak, Peyman Ayoubi
      In performance-based geotechnical earthquake engineering, the required degree and spatial extent of ground densification for mitigation of liquefaction beneath a structure should be determined based on the acceptable levels of performance of foundation. Currently, there is no solution for evaluation of the amount of settlement and tilt of footings constructed on a densified ground which is surrounded by a liquefiable soil. This implies the need for numerical procedures for simulation of seismic behavior of shallow foundations supported on both liquefiable and densified subsoil. In this paper, the dynamic response of shallow foundations on a densified ground is studied using a 3D fully coupled dynamic analysis. For verification of the numerical model, simulation of a series of centrifuge experiments has been carried out and the results were compared with the experimental measurements. After verification of the numerical model, a comprehensive parametric study has been performed to develop a methodology for estimating the effectiveness of subsoil densification in reducing liquefaction-induced settlement of shallow foundations. Range of problem variables were considered in a way that the possibility of bearing capacity failure is low enough. The proposed methodology can be utilized for development of a performance-based design procedure for liquefaction hazard mitigation by soil densification.


      PubDate: 2016-09-22T13:49:00Z
       
  • Experimental analysis of track-ground vibrations on a stretch of the
           Portuguese railway network
    • Abstract: Publication date: November 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 90
      Author(s): N. Correia dos Santos, A. Colaço, P. Alves Costa, R. Calçada
      This paper presents a comprehensive experimental campaign developed on a stretch of the Portuguese railway network. The experimental work includes three fundamental and complementary components: the characterization of the ground, the characterization of the track and the measurement of the vibrations generated by railway traffic. The characterization of the ground was performed using a combination of conventional and geophysical tests (cross-hole and SASW). The mechanical characterization of the track was performed through receptance tests and the rail unevenness profile was accurately measured. The vibrations due to the passage of more than 20 trains were measured. First, a selection of the results is presented and analysed in detail; later, the variability of the responses is briefly discussed. The presented data may be used by other researchers (e.g. in the validation of their prediction models), since it can be downloaded from www.fe.up.pt/~csf/DataCarregado.zip.


      PubDate: 2016-09-22T13:49:00Z
       
  • Nonlinear seismic analysis of irregular r.c. framed buildings
           base-isolated with friction pendulum system under near-fault excitations
    • Abstract: Publication date: November 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 90
      Author(s): Fabio Mazza, Mirko Mazza
      The application of the friction pendulum (FP) system is increasing due to its conceptual simplicity; yet there are still aspects of its behaviour that need further attention. Long duration intense velocity pulses in the horizontal direction and high values of the ratio between vertical and horizontal peak ground acceleration are expected in the near-fault areas. Base-isolated structures subjected to near-fault earthquakes present variation of friction force and lateral stiffness of the FP system during the sliding phase which can induce torsion with residual displacement and uplift. To investigate these effects, a nonlinear dynamic analysis is carried out considering a six-storey reinforced concrete (r.c.) framed building, characterized by an L-shaped plan with wings of different length and setbacks at different heights along the in-plan principal directions. Twelve base-isolated test structures are designed in line with the Italian seismic code, considering (besides the gravity loads) the horizontal seismic loads acting alone or in combination with the vertical ones. Three design values of the radius of curvature and two in-plan distributions of dynamic-fast friction coefficient are assumed for the FP bearings, ranging from a constant value for all isolators to a different value for each. A nonlinear force-displacement law of the FP bearings is considered in the horizontal direction, depending on sliding velocity and axial load, while a gap model takes into account the vertical uplift of the FP bearings. The nonlinear seismic analysis is performed on near-fault ground motions with significant horizontal or vertical components, selected and normalized on the basis of the design hypotheses adopted for the test structure.


      PubDate: 2016-09-17T14:21:16Z
       
  • Soil–structure interaction for a SDOF oscillator supported by a flexible
           foundation embedded in a half-space: Closed-form solution for incident
           plane SH-waves
    • Abstract: Publication date: November 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 90
      Author(s): Jianwen Liang, Liguo Jin, Maria I. Todorovska, Mihailo D. Trifunac
      A closed-form analytical solution is presented for the dynamic response of a SDOF oscillator, supported by a flexible foundation embedded in an elastic half-space, and excited by plane SH waves. The solution is obtained by the wave function expansion method. The solution is verified for the special case of a rigid foundation by comparison with published results. The model is used to investigate the effect of the foundation flexibility on the system response. The results show that the effect is significant for both foundation response and structural relative response. For a system with more flexible foundation, the radiation damping is smaller, the foundation response is larger, especially for obliquely incident waves, while the structural relative response is smaller, and the system frequency shifts towards lower frequencies. This simple model may be helpful to obtain insight into the effects of soil–structure interaction for a slim structure on an extended flexible foundation.


      PubDate: 2016-09-17T14:21:16Z
       
  • A comparative evaluation of design provisions for seismically isolated
           buildings
    • Abstract: Publication date: November 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 90
      Author(s): Cem Yenidogan, Mustafa Erdik
      Seismic isolation method is an innovative mature performance enhancement strategy to mitigate the earthquake risk on structures. As a result of the targeted response modification, feasible engineering solutions can be achieved during the service life of structures. For both bridges and buildings simplified analysis procedure of seismic isolation systems are set forth in guide specifications and design provisions. Equivalent lateral force (ELF) method in buildings can be considered as the simplest method of analysis with high importance. This procedure can be directly used in the analysis and design of seismically isolated structures or it can be used in the establishment of lower-bound limits to nonlinear time history analysis. This paper focuses on the overview of design procedures of isolated buildings and comparison of the analysis results of ELF procedure based on selectively well-known codes and guidelines used in pioneering countries. The buildings were equipped with two commonly used isolation systems named as lead rubber bearing and curved surface friction sliders. A comparison of the 2016 Edition of the Turkish Seismic Design Code with the US(ASCE/SEI 7–10), the European (Italian version of the Eurocode (EC-8) application, NTC-08) and the Japanese (Building Standard Law-2013) codes is conducted on the implementation of the ELF Method for parametric study of structures located at sites of similar probabilistic earthquake hazard in respective countries. Recommendations and concerns associated with the current-state of practice and ongoing development new reference section of TSDC are highlighted by comparing code compliance approaches and practical applications.


      PubDate: 2016-09-17T14:21:16Z
       
  • Transient analysis of concrete gravity dam-reservoir systems by
           Wavenumber-TD approach
    • Abstract: Publication date: November 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 90
      Author(s): Vahid Lotfi, Gerald Zenz
      The Wavenumber approach was initially introduced as an ideal substitute for the rigorous type of analysis which had been the basis of extensive studies in seismic analysis of concrete gravity dams. The former technique is formulated in the context of pure finite element programming, while the latter relies heavily on a two-dimensional semi-infinite fluid element (i.e., hyper-element). Recently, a variation of Wavenumber method was proposed which was referred to as Wavenumber-TD approach. The approximation to the original technique improves its realm of application and allows it to be carried out in time domain as well as frequency domain. In that study, the formulation was examined for harmonic type of excitation which proved to be promising. Herein, this will be evaluated for its real intended application, which is transient analysis of dam-reservoir systems. For this aim, the prepared special purpose finite element program is modified and the analysis of Pine Flat dam is considered as a typical example. Several models are considered with different values of normalized reservoir length. In each case, the reservoir truncation surface is treated by Wavenumber-TD and the extensively utilized Sommerfeld conditions. The dynamic loading considered is the S69E component of Taft earthquake record. Furthermore, two types of reservoir bottom condition of full reflective as well as absorptive, are adopted. Overall, this will allow for a thorough examination and evaluation of Wavenumber-TD approach in regard to its effectiveness.


      PubDate: 2016-09-17T14:21:16Z
       
  • Earthquake damage estimation of concrete gravity dams using linear
           analysis and empirical failure criteria
    • Abstract: Publication date: November 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 90
      Author(s): Mohammad Alembagheri
      A new methodology is proposed to estimate earthquake damage of gravity dams. In this methodology the static pushover analysis is used to formulate a systematic and rational procedure to estimate the level of damage from the linear seismic analysis results. The tensile cracking of concrete is considered as the main potential damage. Examples of three existing concrete gravity dams are provided to illustrate the methodology and discuss the probable nonlinear response and failure mechanisms. The damage state of the dams under twelve proper earthquake ground motions scaled to increasing intensity levels is estimated using the new proposed criteria and verified using the actual nonlinear time-history analysis. Finally, a damage index is defined to quantitatively predict the earthquake damage of gravity dams.


      PubDate: 2016-09-17T14:21:16Z
       
  • Field and large scale laboratory studies on dynamic properties of emplaced
           municipal solid waste from two dump sites at Delhi, India
    • Abstract: Publication date: November 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 90
      Author(s): B.J. Ramaiah, G.V. Ramana, B.K. Bansal
      Dynamic properties of municipal solid waste (MSW) from two dump sites located at Delhi, India are evaluated from field and large scale laboratory tests. Shear wave velocity (V s ) profiles of MSW, measured at these two sites using surface wave techniques, are in range of V s data reported for MSW landfills worldwide. Representative bulk MSW samples were collected from large test pits excavated at the two dump sites to determine the near surface unit weight. Large scale undrained cyclic triaxial (CTX) tests were conducted on reconstituted MSW specimens to investigate the effect of various parameters such as composition, confining pressure, number of loading cycles, loading frequency and saturation on the dynamic properties. Undrained CTX tests, conducted on the specimens with and without fibrous materials demonstrated the effect of fibrous waste constituents on the stiffness and damping behavior of MSW. Specimens consisting of fibrous waste constituents such as plastics and textiles exhibited significantly less modulus reduction compared to specimens with negligible amount of fibrous content. The modulus reduction (G/G max ) and material damping ratio curves derived from the present study are in the range reported for MSW in the literature. The G/G max curves from present study are in good agreement with curves recommended for MSW at Tri-Cities landfill in USA and Tianziling landfill in China. Dynamic properties evaluated from the present study add to the growing database of the worldwide dataset and can be useful for evaluating the seismic stability and associated permanent deformations of the existing dumps in and around Delhi.


      PubDate: 2016-09-17T14:21:16Z
       
  • Anti-plane response induced by an irregular alluvial valley using a hybrid
           method with modified transfinite interpolation
    • Abstract: Publication date: November 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 90
      Author(s): Wen-Shinn Shyu, Tsung-Jen Teng, Chuen-Shii Chou
      This paper proposes a novel strategy for the investigation of displacement amplitude ( u y ) near and along an irregular alluvial valley subjected to shear horizontal (SH) waves. The irregular alluvial valley in this study comprises a partially filled alluvial valley and a circular-arc-layered alluvial valley. Modified transfinite interpolation (MTFI) was used to obtain the coordinates of nodes and determine the sequence of node numbering in the inner finite region, including the irregular alluvial valley. The proposed hybrid method, comprising finite element method and a Lamb series, was applied in conjunction with MTFI to study the effects of irregular alluvial valley geometry, the incident angle of SH waves ( θ ), a dimensionless frequency ( η ), and a filling ratio (FR) on u y . Semi-circular canyons and semi-circular alluvial valleys were also examined. We describe in detail the amplification of u y at the surface of the alluvial valley and discuss the reasons for the formation of the maximum amplitude ( u y max ) as well as its position. Interestingly, FR was shown to play an important role in determining the value of u y , and variations in θ and η dominate the patterns observed in u y . Our numerical simulation results help to elucidate site effects in irregular alluvial valleys as well as a wide range of subjects related to geological structures.
      Graphical abstract image

      PubDate: 2016-09-09T00:45:26Z
       
  • Design and analysis of retaining wall backfilled with shredded tire and
           subjected to earthquake shaking
    • Abstract: Publication date: November 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 90
      Author(s): S. Shrestha, N. Ravichandran, M. Raveendra, J.A. Attenhofer
      The applicability of shredded tire as an economical alternative for conventional granular soil backfill for retaining walls was investigated by conducting geotechnical and structural designs as well as finite element simulations. A literature survey was conducted to compile and document the engineering properties of shredded tire. It was found that the key geotechnical engineering properties vary significantly with shred size and shredding method. Then, a gravity-cantilever retaining wall was designed for dynamic loading conditions considering seismic design parameters corresponding to the Charleston, SC area. Geotechnical design revealed a longer toe compared to heel for shredded tire backfill to maintain stability; however, a shorter footing was needed to maintain overall stability compared to that of granular backfill. Conventional designs and finite element simulations showed significant reductions in computed horizontal deflection at the tip of the wall, structural demand in terms of maximum shear force and bending moment, and construction cost in terms of excavation and material when shredded tire was used as the backfill. Upper and lower bound curves of maximum shear force and maximum bending moment in the stem were also produced based on the results of parametric studies conducted by varying the friction angle and cohesion of shredded tire, and the amplitude and mean period of the input motion.


      PubDate: 2016-09-09T00:45:26Z
       
  • Clarifying the differences between traditional liquefaction hazard maps
           and probabilistic liquefaction reference parameter maps
    • Abstract: Publication date: November 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 90
      Author(s): Kevin W. Franke, Kristin J. Ulmer, Levi T. Ekstrom, Jorge F. Meneses
      Traditional liquefaction hazard maps are useful tools for preliminary engineering site assessment and policy development. However, these maps should not be used for site-specific liquefaction hazard assessment. Simplified probabilistic liquefaction analysis procedures can be used instead to perform site-specific liquefaction hazard assessment, but these procedures rely on probabilistic reference parameter maps that are not yet familiar to most engineering and geological practitioners. As a result, some professionals are questioning the differences between traditional liquefaction hazard maps and the new probabilistic reference parameter maps. This paper clarifies the differences between these two types of maps, and shows how each of these maps complements the other. New probabilistic reference parameter maps for liquefaction triggering and lateral spread displacement are developed and presented for San Diego, California, and simplified probabilistic equations necessary to use the reference parameter maps are summarized. An example map-based liquefaction triggering and lateral spread displacement analysis is performed for a representative site near San Diego Bay. Results of the analysis demonstrate that the probabilistic assessment confirms and augments the information conveyed by the traditional liquefaction hazard map.


      PubDate: 2016-09-09T00:45:26Z
       
  • 3D dynamic finite element analyses and 1g shaking table tests on seismic
           performance of existing group-pile foundation in partially improved
           grounds under dry condition
    • Abstract: Publication date: November 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 90
      Author(s): Kheradi Hamayoon, Yukihiro Morikawa, Ryosuke Oka, Feng Zhang
      Pile foundations are commonly used for heavy superstructures in soft grounds. The failures of pile foundations have been reported in past major earthquakes. An economical and effective method for improving the seismic performance of existing pile foundations is the partial-ground-improvement method (PGI). The main concern of this method is how to determine the size and the location of the areas around a pile foundation to be improved. In this paper, numerical analyses and shaking table tests are conducted to find the optimum pattern for the PGI method. In the numerical analysis, the three-dimensional (3D) dynamic finite element method (FEM) is used with a unified system consisting of a ground, a group-pile foundation and a superstructure. Furthermore, the mechanical behaviors of the ground, the group-pile foundation and the superstructure are modeled by the Cyclic Mobility model, the axial force-dependent model, and the tri-linear model, respectively. With the above-mentioned numerical method, four different patterns of PGI are investigated and then an optimum pattern for the PGI method is proposed. All the numerical analyses are also confirmed by 1g shaking table tests. All the tests and the numerical analyses are conducted under dry condition.


      PubDate: 2016-09-04T15:40:59Z
       
  • Mitigation of liquid sloshing in storage tanks by using a hybrid control
           method
    • Abstract: Publication date: November 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 90
      Author(s): Hao Luo, Ruifu Zhang, Dagen Weng
      In this study, a hybrid method, which simultaneously adjusts structural mass, stiffness, and damping, is proposed to reduce the sloshing of cylindrical tanks under ground motions induced by earthquakes. For this purpose, a viscous mass damper (VMD) is used with a rubber bearing to develop the hybrid control system. Modal and time history analyses are conducted for tanks by using the proposed method. In addition, parametric studies are conducted to investigate the effects of aspect ratio, mass, and damping of the VMD. It is observed that the sloshing heights of the liquid, base shears, and overturning moments of the tanks are reduced through the application of the proposed method. For both slender and broad tanks, the sloshing heights are controlled and the sloshing height can be reduced more in a broad tank. Additionally, a larger equivalent mass of the VMD can help in reducing the sloshing height.


      PubDate: 2016-09-04T15:40:59Z
       
  • Site response analyses using downhole arrays at various seismic hazard
           levels of Singapore
    • Abstract: Publication date: November 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 90
      Author(s): Wenqi Du, Tso-Chien Pan
      Local site conditions can significantly influence the characteristics of seismic ground motions. In this study, site response analyses using one-dimensional linear elastic (LE), equivalent-linear (EQL) and nonlinear (NL) approaches are performed at different seismic hazard levels of Singapore. Two seismic stations, namely, the KAP and BES stations located at soft soil sites, are selected from the national network of Singapore. Firstly, site response estimates using the LE, EQL (SHAKE04) and NL (DEEPSOIL) approaches are compared with the borehole recordings. Results show favorable matches between the predictions and the observations at the KAP site, while under-predictions are observed for all the three site effect approaches at the BES site. Secondly, the applicability of the LE, EQL and NL models is examined at different hazard levels of Singapore. It is found that for the hazard level at a return period of 475 years, the computed maximum strain (γmax) is 0.06% and then the EQL model can provide accurate site response predictions. However, for the hazard level at a return period of 2475 years, the calculated γmax is larger than 2%, resulting in notable differences in the predictions of different site response models. This study highlights the importance of site effects in seismic hazard analysis of Singapore.


      PubDate: 2016-09-04T15:40:59Z
       
  • Probabilistic assessment of ground motions intensity considering soil
           properties uncertainty
    • Abstract: Publication date: November 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 90
      Author(s): Sara Hamidpour, Masoud Soltani
      This paper aims to evaluate the effects of soil uncertainty and soil depth to bedrock on the ground motions intensity. For this, three different depths are considered and the variability of the ground motions characteristics traveling from depth to surface is investigated. Soil maximum shear modulus, G 0, which mainly controls soil stiffness and strength characteristics is considered as the uncertain soil material property. By employing the Monte Carlo (MC) simulation technique and for a defined soil depth, the effect of G 0 variability on the ground motions intensity is investigated. Furthermore, the accuracy of approximate method of First Order Second Moment (FOSM) for response variability estimation is evaluated. Using an approximate method is important because probabilistic analysis methods are commonly very time consuming. By conducting investigations, it's observed that the seismic responses of soil domain including PGA, Amplification Factor (AF) and spectral responses of Single Degree Of Freedom (SODF) system are strongly dependent on the soil depth. Moreover, by comparing the results of FOSM with MC, it is observed that FOSM is able to estimate the responses' variability with acceptable accuracy. Thus, FOSM method could be reasonably used instead of MC simulation technique for predicting the seismic response of the soil domain considering soil G 0 uncertainty.


      PubDate: 2016-09-04T15:40:59Z
       
  • Mechanical models for shear behavior in high damping rubber bearings
    • Abstract: Publication date: November 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 90
      Author(s): Athanasios A. Markou, George D. Manolis
      High damping rubber bearings have been in use for seismic isolation of buildings worldwide for almost 30 years now. In the present work, a brief introduction to the process leading to their manufacturing is first given. Next, a series of novel 1D mechanical models for high damping rubber bearings is proposed, based on the combination of simple and well-known rheological models. These models are calibrated against a set of harmonic tests at strain amplitudes up to 200%. Extension of the models to bidirectional horizontal motion and to time-varying vertical loads is the subject of ongoing work.


      PubDate: 2016-09-04T15:40:59Z
       
  • A study on lateral transient vibration of large diameter piles considering
           pile-soil interaction
    • Abstract: Publication date: November 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 90
      Author(s): Xin Min Chang, Dong Jia liu, Fang Gao, Zhi Tang Lu, Li Li Long, Jian Zhang, Xiao Geng
      This study focuses on the three-dimensional (3-D) characteristics of lateral transient vibration of large diameter piles. Firstly, a 3-D pile-soil model in Cartesian coordinate system is established. Then, the governing equations are established. To eliminate the reflected waves from artificial boundaries, the second-order Higdon absorbing boundary condition is applied herein. Based on the boundary and initial conditions, the numerical solution is obtained using staggered grid finite difference method. The reliability of the numerical simulation is corroborated by comparing calculation results with measured data. It is shown that the optimal sensor location for receiving signal is the center of pile top, which is subjected to the minimum 3-D interference. Dynamic stiffness and damping at pile top are investigated by changing the parameters of pile-soil system.


      PubDate: 2016-09-04T15:40:59Z
       
  • Scattering of SH waves by a shallow rectangular cavity in an elastic half
           space
    • Abstract: Publication date: November 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 90
      Author(s): Qijian Liu, Chao Zhang, Maria I. Todorovska
      Scattering of plane SH waves by a rectangular cavity embedded at shallow depth in an elastic half-space is investigated using a method that is a combination of the wave-function expansion and the weighed residual methods. The proposed method consists of partitioning the half-space using an auxiliary circle that encloses tightly the cavity, representing the motion in each region by a convenient expansion, and determining the coefficients of expansion by imposing continuity of stresses and displacements on the auxiliary circle, which is a transparent boundary. In the four regions inside the circle, representations are used in local coordinate systems such that satisfy automatically the zero-stress condition on the cavity walls, and in the outer region, such that satisfies the radiation condition. The coefficients of expansion are determined approximately, by projecting the displacement and stress residuals along the auxiliary circle onto a set of orthogonal weight functions on [ − π , π ] and setting all projections simultaneously to zero in the least squares sense. The method is verified by comparison with Finite Element Method solutions obtained using ANSYS, and then used to study the effects of the model parameters, such as embedment depth, cavity aspect ratio, frequency and angle of incidence, on the ground surface and cavity wall displacements. While restricted to rectangular cavity shape and still approximate, this method is computationally much more efficient than the Finite Element Method, and therefore is convenient for parametric studies of scattering of seismic waves by rectangular cavities.


      PubDate: 2016-09-04T15:40:59Z
       
  • A note on response of tunnels to incident SH-waves near hillsides
    • Abstract: Publication date: November 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 90
      Author(s): Hasan Faik Kara
      In this study, diffraction of plane SH waves by a cylindrical tunnel embedded in homogeneous, isotropic and linear elastic quarter-space is investigated. Analytical solution techniques are used to solve the two dimensional wave propagation problem. When the excitation is assumed to be harmonic, the governing equation would be the Helmholtz equation. By applying separation of variables method to Helmholtz equation for cylindrical coordinates, general solutions are obtained in terms of Fourier-Bessel series. Unknown complex constants of the Fourier-Bessel series are to be determined from boundary conditions. Boundary conditions at inner and outer side of the tunnel are satisfied directly since they are defined in cylindrical coordinates. Stress-free boundary conditions at the ground and the hillside surfaces are satisfied in closed form via imaging method and addition theorems. Numerical examples are compared with earlier studies and the effect of the tunnel is discussed.


      PubDate: 2016-09-04T15:40:59Z
       
  • An exact solution for three-dimensional (3D) dynamic response of a
           cylindrical lined tunnel in saturated soil to an internal blast load
    • Abstract: Publication date: November 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 90
      Author(s): M. Gao, J.Y. Zhang, Q.S. Chen, G.Y. Gao, J. Yang, D.Y. Li
      The dynamic response of tunnel under internal explosion in reality is a three dimensional geotechnical problem, however, it is often simplified as a plane strain problem in 2D model which can only deal with the dynamic responses of tunnel at the source of explosion. This note proposes a set of exact solutions for three-dimensional (3D) dynamic responses of a cylindrical lined tunnel in saturated soil due to internal blast loading are derived by using Fourier transform and Laplace transform. The surrounding soil is modeled as a saturated medium on the basis of Biot's theory and the lining structure modeled as an elastic medium. By utilizing a reliable and efficient numerical method of inverse Laplace transform and Fourier transform, the numerical solutions for the dynamic response of the lining and surrounding soil are obtained. The 3D dynamic responses of the lined tunnel and the surrounding saturated soil medium due to internal blast loading are then presented and discussed. The results demonstrate that the proposed solutions can help to evaluate the damage of the explosion to surrounding areas of the tunnel in 3D condition at any given elapsed time apart from the section at the source of explosion.


      PubDate: 2016-08-30T15:32:45Z
       
  • Site conditions and earthquake ground motion – A review
    • Abstract: Publication date: November 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 90
      Author(s): Mihailo D. Trifunac
      Studies of the effects of local site conditions on the amplitudes and duration of strong earthquake ground motion have evolved from observations of earthquake damage to buildings. Such studies have involved different degrees of detail and sophistication in how scaling parameters are defined and used. We review the frequently used scaling parameters with an emphasis on the volume of site geology and site soil they represent, the assumptions of one-, two-, or three-dimensional modeling of the associated wave motions, and a linear versus nonlinear site response. We describe the limitations of using only one site parameter, based on the soil properties in the top 30 m, and discuss how the description of site effects could be refined by increasing the number of descriptive parameters and the extent to which those describe deeper geologic structure.


      PubDate: 2016-08-30T15:32:45Z
       
  • Seismic response of a continuous foundation structure supported on
           partially improved foundation soil
    • Abstract: Publication date: November 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 90
      Author(s): Fangyuan Zhou, Huabei Liu, Masafumi Mori, Fukuwa Nobuo, Hongping Zhu
      The response of a continuous foundation structure supported on partially improved foundation soil was recorded during an earthquake. The measured results show that partially improved foundation soil can induce torsional response of the foundation due to the irregular soil-foundation system. A numerical model considering soil-structure interaction was then established, and the numerical results were compared with the observation data. Using the validated numerical model a parametric study was carried out to investigate the torsional response of a continuous foundation structure with irregular soil foundation system. It can be concluded from the study that eccentricities in the soil foundation system would result in a torsional response. Particularly with different lengths of soil-cement piles in the partially improved foundation soil, the generated torsional response can not be ignored during the seismic excitation.


      PubDate: 2016-08-30T15:32:45Z
       
  • Evaluation of substructuring method for seismic soil-structure interaction
           analysis of bridges
    • Abstract: Publication date: November 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 90
      Author(s): Amin Rahmani, Mahdi Taiebat, W.D. Liam Finn, Carlos E. Ventura
      This paper evaluates the commonly used substructuring method for analysis of bridge systems where the bridge is divided into two sub-systems: the bridge superstructure and the substructure including the pile foundations, abutments, and soil. Modeling of the soil-structure interaction (SSI) in the system is simplified by replacing the pile foundations, abutments, and soil with sets of independent equivalent linear springs and dashpots at the base of the superstructure. The main objective of the paper is to examine how well the substructuring method simulates the seismic response of a bridge system. The baseline data required for the evaluation process is derived from analyzing a fully-coupled continuum bridge model, already validated for the instrumented two-span Meloland Road Overpass. The same bridge system is also simulated using the substructuring method. The results from both approaches are compared, and it is shown that the differences between them can be significant. The substructuring method consistently overestimates the pier base shear forces and bending moments and the pier top deflections. Moreover, the spectral response of the bridge structure is mispredicted. The analyses are repeated for a three-span bridge system subjected to several ground motions, leading to a similar observation as before. Hence, the current state of practice for simulating seismic SSI in bridges using the substructure model is shown to be too simplified to capture the major mechanisms involved in SSI.


      PubDate: 2016-08-30T15:32:45Z
       
  • Earthquake induced liquefaction features in the Karewas of Kashmir Valley
           North-West Himalayas, India: Implication to paleoseismicity
    • Abstract: Publication date: November 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 90
      Author(s): Rais Ahmad Khan, Mohammad Yousuf Shah
      Earthquake induced liquefaction features found in the Karewas of Kashmir Valley are potential tools for estimating energy center, magnitude and peak ground acceleration of the paleoearthquakes. Size, pattern and spatial distribution of liquefaction features and in-situ geotechnical data were collected at the paleoliquefaction sites to assess the magnitude and peak ground acceleration of the paleoearthquake. The magnitude of paleoearthquakes was estimated to be of the order of (Mw = 6.2) using “Magnitude bound method” and “In-situ testing of geotechnical properties and assessment of liquefaction potential of liquefied beds (source stratum) using cyclic stress method”. The peak ground acceleration computed were in the range of 0.27g to 0.83g using cyclic stress method and 0.30g using attenuation equation NDMA [21].


      PubDate: 2016-08-30T15:32:45Z
       
  • Optimal design of friction pendulum system properties for isolated
           structures considering different soil conditions
    • Abstract: Publication date: November 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 90
      Author(s): P. Castaldo, M. Ripani
      This study aims at evaluating the optimal properties of friction pendulum bearings to be employed for the seismic protection of elastic isolated structural systems under earthquake excitations with different characteristics in terms of frequency content. A two-degree-of-freedom model is considered to describe the isolated system behavior while accounting for the superstructure flexibility and a non-dimensional formulation of the governing equations of motion is employed to relate the characteristic parameters describing the isolator and structure properties to the response parameters of interest for the performance assessment. Seismic excitations are modeled as time-modulated filtered Gaussian white noise random processes of different intensity within the power spectral density method. The filter parameters control the frequency content of the random excitations and are calibrated to describe stiff, medium and soft soil conditions, respectively. Finally, multi-variate regression expressions are obtained for the optimum values of the friction coefficient that minimize the superstructure displacements relative to the base mass as a function of the structural system properties, of the seismic input intensity and of the soil condition.


      PubDate: 2016-08-30T15:32:45Z
       
  • Effect of numerical soil-foundation-structure modeling on the seismic
           response of a tall bridge pier via pushover analysis
    • Abstract: Publication date: November 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 90
      Author(s): M.R. Falamarz-Sheikhabadi, A. Zerva
      This paper examines the role of the numerical modeling of soil-foundation-structure (SFS) interaction on the seismic response of a tall, partially embedded, flared bridge pier. For this purpose, static, pushover, nonlinear, finite-element, stand-alone analyses are performed on nine different models of one of the two piers of the Mogollon Rim Viaduct, a long-span, reinforced-concrete bridge supported on pile foundations. Structural modeling considerations, such as selection of concrete constitutive models, material properties, and bond-slip and P-Δ effects, on the nonlinear response of this pier are investigated. p-y, t-z and Q-z nonlinear curves are applied to model the soil-pile interaction, and equivalent nonlinear springs are developed to reproduce the soil-pile cap interaction. In addition, the effects of the partial pier embedment and the slope of the ground surface on the lateral resistance of the pier and the total capacity of the SFS system are examined. The results illustrate how structural and geotechnical modeling approaches for the SFS interaction can affect the nonlinear response of tall bridges, and may lead to differences in the numerical prediction of local or global failure. For the case analyzed herein, the partial pier embedment and foundation flexibility can dramatically modify the structural response, and influence the bond-slip effect at the pier-pile cap connection.


      PubDate: 2016-08-30T15:32:45Z
       
  • p-y-ẏ curves for dynamic analysis of offshore wind turbine monopile
           foundations
    • Abstract: Publication date: November 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 90
      Author(s): M. Bayat, L.V. Andersen, L.B. Ibsen
      The well-known p - y curve method provides soil-structure interaction that is independent of the load rate. In this paper an improved p - y curve method is proposed by considering the influence of the excitation frequency. For this purpose, a two-dimensional finite-element program is developed for analysis of a segment of an offshore monopile foundation placed in different depths. The intended use of the model is analyzes of offshore wind turbines in operation where small-magnitude cyclic response is observed in addition to the quasi-static response from the mean wind force. The response to small-magnitude cyclic loading is analyzed by employing coupled equations based on the u - P formulation, i.e. accounting for soil deformation as well as pore pressure. Thus, the paper has focus on the effects of drained versus undrained behavior of the soil and the impact of this behavior on the stiffness and damping related to soil-structure interaction at different load frequencies. In order to enable a parameter study with variation of the soil properties, the constitutive model is purposely kept simple. Hence, a linear poroelastic material model with few material parameters is utilized. Based on the two-dimensional model, linear p - y - y ̇ curves are extracted for the lateral loading of monopiles subjected to cyclic loads. The developed code is verified with findings in the literature.


      PubDate: 2016-08-30T15:32:45Z
       
  • Response of Marmaray Submerged Tunnel during 2014 Northern Aegean
           Earthquake (Mw=6.9)
    • Abstract: Publication date: November 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 90
      Author(s): S.U. Dikmen
      For the resilience of communities against natural hazards, it is important that the critical structures perform as per their design objectives. Thus continuous monitoring of these structures is important to identify changes in their behavior and/or response characteristics. In this respect, low intensity earthquakes provide valuable information about the performance of the monitoring systems and the structure being monitored. Marmaray Submerged Tunnel (MST), which is considered to be one of the major engineering achievements of the recent years, forms an important link in Istanbul's transportation network. This paper presents a study made on the response of MST during the May 24, 2014 Northern Aegean Earthquake (Mw=6.9) that occurred 300km away from MST. The data used in the study are obtained from the seismic monitoring system of MST and Istanbul earthquake rapid response network.


      PubDate: 2016-08-30T15:32:45Z
       
  • Earthquake response of solitary slender freestanding intake towers
    • Abstract: Publication date: November 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 90
      Author(s): Mohammad Alembagheri
      Earthquake response of solitary slender intake towers is investigated considering an idealized hollow intake tower with its circular footing submerged in water. The tower is studied in anchored (fixed base) and unanchored (freestanding) states placed on undeformable soil foundation. The water-structure interaction is modeled by the Eulerian-Lagrangian approach, using the pressure-based elements for the water and the displacement-based elements for the structure. The only source of nonlinearity is the contact at the base joint between the tower's footing and the ground. This contact is modeled using Coulomb friction model which allows the tower to slide and uplift. The system is three-dimensionally analyzed using finite element method under static and dynamic earthquake loads. A detailed parametric study is conducted to assess the importance of system characteristics including surrounding and inside water levels, ratio of tower height to footing radius, base joint friction coefficient, water compressibility, footing flexibility, and vertical ground motion.


      PubDate: 2016-08-26T10:40:48Z
       
  • The effect of boundary conditions, model size and damping models in the
           finite element modelling of a moving load on a track/ground system
    • Abstract: Publication date: October 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 89
      Author(s): J.Y. Shih, D.J. Thompson, A. Zervos
      An investigation is presented of the use of finite element models in the time domain to represent a load moving on a railway track on a flexible ground. A systematic study is carried out to compare different sizes and shapes of finite element mesh, different boundary conditions intended for suppressing reflections from the truncated model boundaries, and different models of soil damping. The purpose is to develop guidance to assist in selecting appropriate finite element models for moving load problems. To prevent reflections from the boundaries of the finite domain two approaches are compared. A 40m radius hemispherical finite element mesh has been used first with infinite elements around the perimeter. This approach gives good results for a point harmonic load at the centre of the domain but some problems are highlighted when it is used for moving load calculations. An alternative approach has therefore been investigated based on a cuboid mesh. The base was fixed to prevent rigid-body motions of the model and, rather than use infinite elements at the sides, these were also fixed. It is shown that, provided that a suitable damping model is used, the spurious reflections from the sides of the model can be suppressed if the model is wide enough. On the other hand, if infinite elements are used, the calculations are found to be considerably more costly with little added benefit. Different models of soil damping are also compared. It is shown that a mass-proportional damping model gives a decay with distance that is independent of frequency, making it particularly suitable for this application. The length of model required to achieve steady state has been investigated. For a homogeneous half-space it is found that the required length increases considerably in the vicinity of the critical speed, up to 130m in the present example, whereas for the layered ground a more modest length is sufficient for all speeds.


      PubDate: 2016-08-11T09:42:32Z
       
  • Seismic control of irregular multistory buildings using active tendons
           considering soil–structure interaction effect
    • Abstract: Publication date: October 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 89
      Author(s): Ebrahim Nazarimofrad, Seyed Mehdi Zahrai
      Much research has been conducted in recent decades on structural control to improve the performance of different towers and high-rise buildings against severe earthquakes and strong winds. Most studies on building vibration control have been considered just two-dimensionally using shear frame models. In reality, most of the buildings might have irregular plans and thus experience torsion when subjected to earthquakes. Such torsion would further increase the structural response. On the other hand, some buildings are located on soft soil that would trigger the soil-structure interaction (SSI) effects required to be considered for design purposes. The main dynamic behavior parameters like natural frequencies, damping ratios and mode shapes would depend on construction site conditions and thus the SSI effects must be taken into account for buildings on soft soil. In this paper, a mathematical model is developed for calculating the seismic response of an irregular multi-story building equipped with active tendons. The SSI effect is then introduced by changing structure mass, stiffness and damping matrices. The model is employed to obtain the seismic response of 10-story buildings using active tendon with LQR algorithm. The building is modeled as a structure composed of members connected by rigid floor diaphragms with three degrees of freedom at each story; i.e. lateral displacements in two perpendicular directions and a rotation with respect to a vertical axis. Results showed that active tendons have low effects on the reduction of structural response when the building has been located on soft soils.


      PubDate: 2016-08-11T09:42:32Z
       
  • An energy flow study of a double-deck tunnel under quasi-static and
           harmonic excitations
    • Abstract: Publication date: October 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 89
      Author(s): Arnau Clot, Jordi Romeu, Robert Arcos
      This paper presents a comparison between the vibration energy flow radiated by a double-deck tunnel and the one radiated by a simple tunnel when both are excited by constant or by harmonic moving loads. For both cases, the radiated energy is computed using a three-dimensional semi-analytical model of the system. The total energy radiated upwards is presented for a wide range of load speeds, when a constant moving load is considered, and for a wide range of excitation frequencies, when the excitation is a harmonic moving load. Significant differences have been obtained, first, for constant loads moving at very high speeds and, second, for harmonic loads moving at typical speeds for underground trains.


      PubDate: 2016-08-11T09:42:32Z
       
  • Procedure for selecting and modifying earthquake motions to multiple
           intensity measures
    • Abstract: Publication date: October 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 89
      Author(s): Richard J. Armstrong
      A new ground motion selection and modification procedure is presented that selects a set of ground motions to capture multiple intensity measure targets. The ground motion selection and modification procedure involves selecting a set of candidate ground motions scaled to a conditioning intensity measure that is subsequently trimmed down using a semi-automated selection process to reach a final set that satisfies statistical considerations. The new procedure is relatively straightforward to implement using common tools and knowledge yet is still based on the principles of conditioning and on aspects of previously-developed selection and modification procedures. A single example is provided to demonstrate the use of these concepts to ground motion development.


      PubDate: 2016-08-11T09:42:32Z
       
  • 2D non-linear seismic response of the Dinar basin,TURKEY
    • Abstract: Publication date: October 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 89
      Author(s): H. Khanbabazadeh, R. Iyisan, A. Ansal, M.E. Hasal
      Local geological conditions generate significant amplification of ground motion and concentrated damage during earthquakes. The highly concentrated damages at the edges of the Dinar basin during occurred earthquakes at regions close to rock outcrop bring up the effect of the inclined bedrock effect on the dynamic behavior of the basin with 2D geometry. In this study, first the idealized 2D model of the basin based on the results of the underground explorations and geologic investigations is proposed. Results show that Dinar basin has an asymmetric 2D geometry with two different bedrock angles at edges. Then, a numerical study using finite difference based nonlinear code which utilizes appropriate static and dynamic boundary conditions, and includes hysteresis damping formulation based on the user defined degradation curves is conducted using real earthquake motions of different strength and frequency content. The constructed model is subjected to the collection of 16 earthquakes with different PGA's of 0.1, 0.2, 0.3 and 0.4g, four motions for each PGA. It was seen that the dynamic behavior of the basin is broadly affected by the two dimensional bedrock. The results indicates the higher effect of the 6° bedrock inclination at east part on the amplification with respect to the steeper 20° bedrock slope at the west. Also, the results show the insignificant effect of the bedrock at the depth more than 150m on the amplification of the east edge. While the effect of the 6° bedrock angle at the east part continues until 1500m from the outcrop, it affects the amplification until 700m from the outcrop at the west part with 20° bedrock angle.


      PubDate: 2016-08-11T09:42:32Z
       
  • Boundary reaction method for nonlinear analysis of soil–structure
           interaction under earthquake loads
    • Abstract: Publication date: October 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 89
      Author(s): Jae-min Kim, Eun-haeng Lee, Sang-hoon Lee
      This paper presents a boundary reaction method (BRM) for nonlinear time domain analysis of soil–structure interaction (SSI) under incident seismic waves. The BRM is a hybrid frequency–time domain method, but it removes global iterations between frequency and time domain analyses commonly required in the hybrid approach, so that it operates as a two-step uncoupled method. Specifically, the nonlinear SSI system is represented as a simple summation of two substructures as follows: (I) wave scattering substructure subjected to incident seismic waves to calculate boundary reaction forces on the fixed interface boundary between a finite nonlinear structure-soil body and an unbounded linear domain; and (II) wave radiation substructure subjected to the boundary reaction forces in which the nonlinearities can be considered. The nonlinear responses in the structure–soil body can be obtained by solving the radiation problem in the time domain using a general-purpose nonlinear finite element code that can simulate absorbing boundary conditions, while the boundary reaction forces can be easily calculated by solving the linear scattering problem by means of a standard frequency domain SSI code. The BRM is verified by comparing the numerical results obtained by the proposed BRM and the conventional frequency-domain SSI analysis for an equivalent linear SSI system. Finally, the BRM is applied to the nonlinear time-domain seismic analysis of a base-isolated nuclear power plant structure supported by a layered soil medium. The numerical results showed that the proposed method is very effective for nonlinear time-domain SSI analyses of nonlinear structure-soil system subjected to earthquake loadings.


      PubDate: 2016-08-11T09:42:32Z
       
  • Soil-pile-structure kinematic and inertial interaction observed in
           geotechnical centrifuge experiments
    • Abstract: Publication date: October 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 89
      Author(s): Mahmoud N. Hussien, Tetsuo Tobita, Susumu Iai, Mourad Karray
      This paper reports the results of a series of centrifuge tests examining dynamic responses of single and 3×3 grouped piles embedded in sand and supporting SDOF and 2DOF structures. A total of 7 model tests were conducted with the centrifugal acceleration of 40 g. Each model was subjected to 12 sinusoidal waves with constant acceleration amplitude and varying frequencies. The results of the tests indicate that pile-head motion is dominated by two sequential frequencies: a lower frequency (f SSI) where pile-head motion is substantially maximized and a higher one (f pSSI) where the response is minimized with respect to free field surface motion. These results confirm recent published numerical results on single piles supporting SDOF structures and generalize their findings to grouped piles supporting SDOF and 2DOF structures. The results show also strong mobilized kinematic interaction effect generating significant pile bending when the ground is excited at its resonant frequency. On the other hand, structural vibrations tend to impose large bending moments as the excitation frequency approaches the natural frequency of the coupled soil-pile-structure system. Distribution of pile bending moments in the group is found to be a function of the pile position and the excitation frequency. In contrast to inner piles having the greatest kinematic bending moments, outer piles have a more pronounced inertial ones.


      PubDate: 2016-08-11T09:42:32Z
       
  • Computation of degradation factors of p-y curves in liquefiable soils for
           analysis of piles using three-dimensional finite-element model
    • Abstract: Publication date: October 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 89
      Author(s): Asskar Janalizadeh Choobbasti, Ali Zahmatkesh
      This paper presents a procedure to compute the values of degradation factors of p-y curves in the pseudo-static analysis of piles in liquefiable soils. Three-dimensional finite-element model was used for the computation of p and y values using OpenSees computer package. The piles were modeled using beam-column elements and elastic section. The soil continuum was modeled using brick elements and a two-surface plasticity model. By comparing the results of models in two cases of liquefiable and non-liquefiable, values of degradation factors were obtained. Validation of the degradation factors computed was conducted through the centrifuge test results. The simulation results showed a similar trend between degradation factor variation in different densities and sands. With increasing depth, the degradation factor increased. By comparing the results of pseudo-static analysis with the centrifuge test results, it was concluded that the use of the p-y curves with computed degradation factors in liquefiable sand gave reasonable results.


      PubDate: 2016-08-11T09:42:32Z
       
  • Assessment of seismic liquefaction potential based on Bayesian network
           constructed from domain knowledge and history data
    • Abstract: Publication date: October 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 89
      Author(s): Ji-Lei Hu, Xiao-Wei Tang, Jiang-Nan Qiu
      Prediction of seismic liquefaction is difficult due to the uncertainties and complexity of multiple related factors. Bayesian network is a just right effective tool to deal the problem because of merging multiple source information and domain knowledge in a consistent system, reflecting and analyzing the interdependent uncertain relationships between variables. This paper used two ways to construct generic Bayesian network models with twelve significant factors of seismic liquefaction, of which the first model is constructed only by interpretive structural modeling and causal mapping approach for incomplete data contained huge missing values. Another one is constructed by combining K2 algorithm and domain knowledge for complete data. Compared with artificial neural network and support vector machine using 5-fold cross-validation, the two Bayesian network models provided a better performance, and the second Bayesian network model is slightly better than the first one. This paper also offers a sensitivity analysis of the input factors. In the twelve variables, standard penetration test number, soil type, vertical effective stress, depth of soil deposit, and peak ground acceleration have more significant influences on seismic liquefaction than others. Our results suggest that the Bayesian network is useful for prediction of seismic liquefaction and is simple to perform in practice.


      PubDate: 2016-08-11T09:42:32Z
       
  • Wave propagation with energy diffusion in a fractal solid and its
           fractional image
    • Abstract: Publication date: October 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 89
      Author(s): Gerd Gudehus, Asterios Touplikiotis
      Crucial features of seismograms and spectra with small amplitudes are explained by means of fractality and fractional calculus. Wave propagations in the elastic range of porous solids imply precursors and followers of coherent waves. They result from a non-local diffraction via force chains which is called energy diffusion. Such phenomena are captured by fractional wave equations which are deduced by means of an elastic energy and the balance of momentum for random fractal ensembles. Theoretical propagations imply precursors which were similarly observed with bender elements, and a rate of dissipation nearly proportional to the kinetic energy which suits to resonant column test results. A novel three-dimensional fractional Dirichlet-Green function implies primary and secondary wave crests with speed and alignment which do not depend on the fractal dimension. Power spectra in the dislocation-free far-field of seismogeneous chain reactions and impacts tend to a fractality-dependent power law with a peak-like cutoff, both theoretically and observed, therein a modified Huygen’s principle is employed. Limitations are discussed and possible extensions are indicated.


      PubDate: 2016-08-11T09:42:32Z
       
  • Experimental evaluation of vulnerability for urban segmental tunnels
           subjected to normal surface faulting
    • Abstract: Publication date: October 2016
      Source:Soil Dynamics and Earthquake Engineering, Volume 89
      Author(s): Majid Kiani, Abbas Ghalandarzadeh, Tohid Akhlaghi, Mohammad Ahmadi
      Faulting is one type of permanent ground displacement (PGD); tunnels are at the risk of damage when they are susceptible to faulting. The present study proposes an experimental approach to create the fragility curves for shallow segmental tunnels in alluvial deposits subjected to normal surface faulting. Centrifuge testing was carried out in order to achieve this purpose. The proposed approach allows evaluation of new fragility curves considering the distinctive features of tunnel geometry and fault specifications. The comparison between the new fragility curves and the existing empirical curves was discussed as well. Compared to tunnels in rock, tunnels in alluvial deposits are more susceptible to failure because of different mechanisms of collapse into tunnel at large exerted PGD.


      PubDate: 2016-08-11T09:42:32Z
       
 
 
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