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  Subjects -> EARTH SCIENCES (Total: 610 journals)
    - EARTH SCIENCES (449 journals)
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EARTH SCIENCES (449 journals)            First | 1 2 3 4 5     

Memoirs of the Association of Australasian Palaeontologists     Full-text available via subscription   (Followers: 2)
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Meteorologische Zeitschrift     Full-text available via subscription   (Followers: 2)
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Momona Ethiopian Journal of Science     Open Access   (Followers: 2)
Moscow University Geology Bulletin     Hybrid Journal  
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Mountain Research and Development     Open Access   (Followers: 3)
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Natural Hazards Review     Full-text available via subscription   (Followers: 10)
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Open Journal of Earthquake Research     Open Access  
Open Journal of Soil Science     Open Access   (Followers: 4)
Ore Geology Reviews     Hybrid Journal   (Followers: 3)
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Revista Boletín Ciencias de la Tierra     Open Access   (Followers: 2)
Revista Brasileira de Geofísica     Open Access   (Followers: 4)
Revista de Ingenieria Sismica     Open Access  
Revista de la Sociedad Entomologica Argentina     Open Access   (Followers: 2)
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Revista Geológica de Chile     Open Access   (Followers: 2)
River Systems     Full-text available via subscription   (Followers: 3)
Rock Mechanics and Rock Engineering     Hybrid Journal   (Followers: 6)
Rocks & Minerals     Hybrid Journal   (Followers: 2)
Russian Geology and Geophysics     Hybrid Journal   (Followers: 2)
Russian Journal of Mathematical Physics     Hybrid Journal  
Russian Journal of Pacific Geology     Hybrid Journal   (Followers: 1)
Russian Physics Journal     Hybrid Journal  
Science China Earth Sciences     Hybrid Journal   (Followers: 2)
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Scientific Annals of Stefan cel Mare University of Suceava. Geography Series     Open Access  
Scientific Journal of Earth Science     Open Access   (Followers: 1)

  First | 1 2 3 4 5     

Journal Cover Soil Dynamics and Earthquake Engineering     [SJR: 1.116]   [H-I: 39]
   [10 followers]  Follow    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0267-7261
   Published by Elsevier Homepage  [2582 journals]
  • Improved simplified calibration procedure for a high-cycle accumulation
           model
    • Abstract: Publication date: March 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 70
      Author(s): T. Wichtmann , A. Niemunis , T. Triantafyllidis
      The high-cycle accumulation (HCA) model proposed by Niemunis et al. [16] predicts permanent deformations due to a drained cyclic loading with many small cycles (i.e. N ≥ 10 3 cycles with strain amplitudes ε ampl ≤ 10 − 3 ). The strain amplitude is the most important influencing parameter of the rate of strain accumulation ε ̇ acc . Based on tests on a medium coarse sand, a square relationship ε ̇ acc ~ ( ε ampl ) 2 has been used in the HCA model so far. The new test results presented in this paper indicate, however, that the exponent of the amplitude-dependence may vary between 1.3 and 2.4, depending on the tested material. This comes out of 150 drained cyclic triaxial tests with 105 load cycles performed on 14 clean quartz sands with specially mixed grain size distribution curves. Consequently, an additional material constant C ampl has been introduced into the HCA model describing the amplitude dependence according to ε ̇ acc ~ ( ε ampl ) C ampl . The additional parameter requires a revision of the simplified calibration procedure proposed by Wichtmann et al. [24] which uses correlations between the HCA model parameters and granulometric (d 50, C u ) or index properties ( e min ). Furthermore, the new cyclic test data reveal that the existing correlations are inappropriate for well-graded granular materials ( C u ≥ 5 ). Enhanced correlations suitable also for more well-graded sands are proposed in the paper. The possible error of a HCA model prediction with parameters fully or partly determined from the correlations is discussed.


      PubDate: 2015-01-21T11:12:53Z
       
  • Soil-structure interaction using BEM–FEM coupling through ANSYS
           software package
    • Abstract: Publication date: March 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 70
      Author(s): G. Vasilev , S. Parvanova , P. Dineva , F. Wuttke
      The main aim of this work is to develop, verify and apply in simulation study an efficient hybrid approach to study seismic response of a soil-structure system taking into account all the important components as: (1) the line time-harmonic source with its specific geophysical properties; (2) the inhomogeneity and heterogeneity of the wave path from the source to the local geological region; (3) the geotechnical properties of the near-field local geological profile and finally (4) the properties of the engineering structure itself. Plane strain state is considered. The hybrid computational tool is based on the boundary element method (BEM 1 1 Boundary element method. ) for modeling the infinite far-field geological media and finite element method (FEM 2 2 Finite element method. ) for treating the dynamic behavior of the structure and the near-field finite soil geological region. Each of the two techniques is applied in that part of the whole model where it works more efficiently. The hybrid numerical scheme is realized via the sub-structure approach, direct BEM1, conventional FEM2 and insertion of the BEM1 model of the seismically active far-field geological media as a macro-finite element (MFE 3 3 Macro-finite element. ) in the FEM2 commercial program ANSYS. The accuracy and verification study of the proposed method is presented by solution of numerical test examples simulating different seismic scenarios. The obtained results show clearly that the hybrid model is able to demonstrate the sensitivity of the synthetic signals to the source properties, to the heterogeneous character of the wave path, to the relief peculiarities of the local layered geological deposit and to the specific properties of the engineering structure.


      PubDate: 2015-01-21T11:12:53Z
       
  • Cyclic secant shear modulus versus pore water pressure in sands at small
           cyclic strains
    • Abstract: Publication date: March 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 70
      Author(s): Mladen Vucetic , Ahmadreza Mortezaie
      Cyclic strain-controlled behavior of fully saturated sands in undrained condition is analyzed at small cyclic shear strain amplitudes, γ c, around the threshold shear strain for cyclic pore water pressure buildup, γ tp≈0.01%. The cyclic triaxial and simple shear test results obtained in the past by different researchers and the results of new cyclic simple shear tests reveal that: (i) at very small γ c below γ tp where there is no buildup of cyclic pore water pressure, Δu N, with the number of cycles, N, the cyclic secant shear modulus, G SN, initially increases with N for 10–20% of its initial value G S1 and then levels off or just slightly decreases, (ii) at small γ c between γ tp≈0.01% and 0.10–0.15%, Δu N continuously increases with N while the modulus G SN first increases for up to 10% of G S1 and then gradually decreases, and (iii) at γ c larger than approximately 0.15%, relatively large Δu N develops with N while the modulus G SN constantly and significantly decreases. This means that at γ c between γ tp and 0.10–0.15% the sand stiffness initially increases with N in spite of the reduction of effective stresses caused by the cyclic pore water pressures buildup. In this range of γ c, the pore water pressure Δu N can reach up to 40% of the initial effective confining stress before G SN drops below G S1. The microstructural mechanisms believed to be responsible for such a complex behavior are discussed. It is suggested that during cyclic loading the changes at mineral-to-mineral junctions of grain contacts can cause soil stiffening while, at the same time, the buildup of cyclic pore water pressure causes the softening.


      PubDate: 2015-01-16T05:56:34Z
       
  • General formulation and solution procedure for harmonic response of rigid
           foundation on isotropic as well as anisotropic multilayered half-space
    • Abstract: Publication date: March 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 70
      Author(s): Gao Lin , Zejun Han , Jianbo Li
      A general formulation and solution procedure are proposed for harmonic response of rigid foundation on multilayered half-space. It is suitable for isotropic as well as anisotropic soil medium. The wave motion equation is formulated in frequency wave-number domain in the state space. A hybrid approach is proposed for its solution, where the precise integration algorithm (PIA) is employed to carry out the integration. Very high accuracy can be achieved. The mixed variable form of wave motion equation enables the assembly of layers simple and convenient. The surface Green׳s function is regarded as rigorous, because it is free from approximations and discretization errors. The algorithm is unconditionally stable. The numerical implementation is based on algebraic matrix operation. Numerical examples of vibration of rigid foundation validate the efficiency and accuracy of the proposed approach.
      Graphical abstract image

      PubDate: 2015-01-16T05:56:34Z
       
  • Evaluation of active and passive seismic earth pressures considering
           internal friction and cohesion
    • Abstract: Publication date: March 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 70
      Author(s): Shi-Yu Xu , Anoosh Shamsabadi , Ertugrul Taciroglu
      The Log-Spiral-Rankine (LSR) model, which is a generalized formulation for assessing the active and passive seismic earth pressures considering the internal friction and cohesion of backfill soil, is reviewed and improved in this study. System inconsistencies in the LSR model are identified, which result from an inaccurate assumption on the vertical normal stress field (σ z =γz) in a general c–ϕ soil medium, and from omitting the effect of soil cohesion when solving for the stress states along the failure surface. The remedies to the said inconsistencies are presented, and local and global iteration schemes are introduced to solve the resulting highly coupled multivariate nonlinear system of equations. The modified LSR model provides a more complete and accurate solution for earth retaining systems, including the geometry of the mobilized soil body, the stress state along the failure surface, as well as the magnitude and the point of application of the resultant earth thrust.


      PubDate: 2015-01-16T05:56:34Z
       
  • Dynamic response of a geotechnical rigid model container with absorbing
           boundaries
    • Abstract: Publication date: February 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 69
      Author(s): Domenico Lombardi , Subhamoy Bhattacharya , Fabrizio Scarpa , Matteo Bianchi
      One of the major challenges encountered in earthquake geotechnical physical modelling is to determine the effects induced by the artificial boundaries of the soil container on the dynamic response of the soil deposit. Over the past years, the use of absorbing material for minimising boundaries effects has become an increasing alternative solution, yet little systematic research has been carried out to quantify the dynamic performance of the absorbing material and the amount of energy dissipated by it. This paper aims to examine the effects induced by the absorbing material on the dynamic response of the soil, and estimate the amount of energy reduced by the absorbing boundaries. The absorbent material consisted of panels made of commercially available foams, which were placed on both inner sides of end-walls of the soil container. These walls are perpendicular to the shaking direction. Three types of foam with different mechanical properties were used in this study. The results were obtained from tests carried out using a shaking table and Redhill 110 sand for the soil deposit. It was found that a considerably amount of energy was dissipated, in particular within the frequency range close to the resonance of the soil deposit. This feature suggests that the presence of foams provides a significant influence to the dynamic response of the soil. The energy absorbed by the boundaries was also quantified from integrals of the Power Spectral Density of the accelerations. It was found that the absorbed energy ranged between a minimum of 41% to a maximum of 92% of the input levels, depending mainly on the foam used in the test. The effects provided by the acceleration levels and depth at which the energy was evaluated were practically negligible. Finally, practical guidelines for the selection of the absorbing material are provided.


      PubDate: 2015-01-16T05:56:34Z
       
  • Effect of a forced harmonic vibration pile to its adjacent pile in layered
           elastic soil with double-shear model
    • Abstract: Publication date: December 2014
      Source:Soil Dynamics and Earthquake Engineering, Volume 67
      Author(s): Jue Wang , S.H. Lo , Ding Zhou
      A new model named double-shear model based on Pasternak foundation and Timoshenko beam theory is developed to evaluate the effect of a forced harmonic vibration pile to its adjacent pile in multilayered soil medium. The double-shear model takes into account the shear deformation and the rotational inertia of piles as well as the shear deformation of soil. The piles are simulated as Timoshenko beams, which are embedded in a layered Pasternak foundation. The differential equation of transverse vibration for a pile is solved by the initial parameter method. The dynamic interaction factors for the layered soil medium are obtained by the transfer matrix method. The formulation and the implementation have been verified by means of several examples. The individual shear effects of soil and piles on the interaction factors are evaluated through a parametric study. Compared to Winkler model with Euler beam, the present model gives much better results for the dynamic interaction of piles embedded in stiff soil with small slenderness ratios. Finally, the effect of a forced long pile to a short pile embedded in multilayered soil medium is studied in detail.


      PubDate: 2015-01-16T05:56:34Z
       
  • Constrained optimization for 1-D dynamic and earthquake response analysis
           of hybrid base-isolation systems
    • Abstract: Publication date: December 2014
      Source:Soil Dynamics and Earthquake Engineering, Volume 67
      Author(s): Giuseppe Oliveto , Nicholas D Oliveto , Anastasia Athanasiou
      The paper presents a constrained optimization procedure (COP) for the dynamic analysis of hybrid base isolation systems under earthquake excitation. After a description of the hybrid system considered, the mechanical model used for its representation is introduced, along with the governing equations. Mid-point central difference time-discretization is used to cast the computations in each time increment as a quadratic optimization problem with non-linear constraints. Numerical applications illustrate the accuracy and robustness of the formulation and highlight some typical performance characteristics of hybrid base isolation systems.


      PubDate: 2015-01-16T05:56:34Z
       
  • Stability analysis of a slope subject to real accelerograms by finite
           elements. Application to San Pedro cliff at the Alhambra in Granada
    • Abstract: Publication date: February 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 69
      Author(s): Antonio Morales-Esteban , José Luis de Justo , J. Reyes , J. Miguel Azañón , Percy Durand , Francisco Martínez-Álvarez
      The dynamic stability analysis of slopes is often conducted by the traditional method of slices, using pseudo-static calculations. However, the response of a geotechnical structure subjected to seismic loads can be studied through a dynamic finite element analysis, which can be considered one of the most complete available tools, as information about the stress distribution and the deformations can be obtained. The dynamic analysis of the stability of San Pedro cliff at the Alhambra in Granada is studied in this paper. The results have been compared with pseudo-static calculations worked out with the method of slices. Real accelerograms have been selected for the dynamic tests. Thorough in situ and laboratory tests have been conducted in order to properly characterize the cliff. The soil constitutive model is also explained in this paper. Finally, the influence of the sources of energy dissipation has been studied through the material damping, the integration scheme and the boundary conditions.


      PubDate: 2015-01-16T05:56:34Z
       
  • Dispersion of shear wave propagating in vertically heterogeneous double
           layers overlying an initially stressed isotropic half-space
    • Abstract: Publication date: February 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 69
      Author(s): Abhishek Kumar Singh , Amrita Das , Amares Chattopadhyay , Sudarshan Dhua
      The present paper investigates the propagation of horizontally polarised shear wave in distinct vertically heterogeneous double layers overlying an isotropic half-space under horizontal initial stress. The vertical heterogeneity in the uppermost layer is caused due to quadratic variation only in rigidity, whereas vertical heterogeneity in the sandwiched layer is caused due to exponential variation in rigidity and density both. The closed form of velocity equation is obtained which leads to the dispersion equation as its real part and damping equation as its imaginary part. The validation of dispersion relation with the classical case is made by using Debye asymptotic expansion which is the major highlight of this study. The significant effect of the width ratio of the layers, heterogeneity parameters of both the layers and horizontal compressive/tensile initial stress on the phase velocity and damped velocity of SH-wave have been traced out. The comparative study and some important peculiarities have been revealed by means of graphical illustrations.


      PubDate: 2015-01-16T05:56:34Z
       
  • Editorial Board / Aims and Scope
    • Abstract: Publication date: February 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 69




      PubDate: 2015-01-16T05:56:34Z
       
  • A pushover procedure for seismic assessment of buildings with bi-axial
           eccentricity under bi-directional seismic excitation
    • Abstract: Publication date: February 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 69
      Author(s): Kazem Shakeri , Samaneh Ghorbani
      A new modal pushover procedure is proposed for seismic assessment of asymmetric-plan buildings under bi-directional ground motions. Although the proposed procedure is a multi-mode procedure and the effects of the higher and torsional modes are considered, the simplicity of the pushover procedure is kept and the method requires only a single-run pushover analysis for each direction of excitation. The effects of the frequency content of a specific ground motion and the interaction between modes at each direction are all considered in the single-run pushover analysis. For each direction, the load pattern is derived from the combined modal story shear and torque profiles. The pushover analysis is conducted independently for each direction of motion (x and y), and then the responses due to excitation in each direction are combined using SRSS (Square Roots of Sum of Squares) combination rule. Accuracy of the proposed procedure is evaluated through two low- and medium-rise buildings with 10% two-way eccentricity under different pairs of ground motions. The results show promising accuracy for the proposed method in predicting the peak seismic responses of the sample buildings.


      PubDate: 2015-01-16T05:56:34Z
       
  • Elastic waves in continuous and discontinuous geological media by boundary
           integral equation methods: A review
    • Abstract: Publication date: March 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 70
      Author(s): George D. Manolis , Petia S. Dineva
      In this review paper, we concentrate on the use of boundary integral equation (BIE) based methods for the numerical modeling of elastic wave motion in naturally occurring media. The main reason for using BIE is the presence of the free surface of the earth, whereby large categories of problems involve continua with a small surface to volume ratio. Given that under most circumstances, BIE require surface discretization only, substantial savings can be realized in terms of the size of the mesh resulting from the discretization procedure as compared to domain-type numerical methods. We note that this is not necessarily the case with man-made materials that have finite boundaries. Thus, although the emphasis here is on wave motion in geological media, this review is potentially of interest to researchers working in other scientific fields such as material science. Most of the material referenced in this reviews drawn from research work conducted in the last fifteen years, i.e., since the year 2000, but for reasons of completeness reference is made to seminal papers and books dating since the early 1970s. Furthermore, we include here methods other than the BIE-based ones, in order to better explain all the constituent parts of hybrid methods. These have become quite popular in recent years because they seem to combine the best features of surface-only discretization techniques with those of domain type approaches such as finite elements and finite differences. The result is a more rounded approach to the subject of elastic wave motion, which is the underlying foundation of all problems that have to do with time-dependent phenomena in solids.


      PubDate: 2015-01-16T05:56:34Z
       
  • Discussion on “Implications of surface wave data measurement
           uncertainty on seismic ground response analysis” by Jakka et al.
    • Abstract: Publication date: Available online 16 December 2014
      Source:Soil Dynamics and Earthquake Engineering
      Author(s): Cesare Comina , Sebastiano Foti
      The discussion deals with the effect of shear wave velocity uncertainties on 1D seismic ground response analysis. In particular, the paper refers to uncertainties deriving from the solution of the inverse problem in surface wave methods. We address some issues related to the evaluation of “equivalent” profiles from surface wave data, the inversion strategy and the numerical simulation of seismic site response. The pitfalls in the analyses point out the need for more refined studies to draw general conclusions on the subject.


      PubDate: 2015-01-16T05:56:34Z
       
  • Editorial Board / Aims and Scope
    • Abstract: Publication date: December 2014
      Source:Soil Dynamics and Earthquake Engineering, Volume 67




      PubDate: 2015-01-16T05:56:34Z
       
  • Seismic behaviour of circular tunnels accounting for above ground
           structures interaction effects
    • Abstract: Publication date: December 2014
      Source:Soil Dynamics and Earthquake Engineering, Volume 67
      Author(s): Kyriazis Pitilakis , Grigorios Tsinidis , Andrea Leanza , Michele Maugeri
      Tunnels are commonly designed under seismic loading assuming “free field conditions”. However, in urban areas these structures pass beneath buildings, often high-rise ones, or are located close to them. During seismic excitation, above ground structures may cause complex interaction effects with the tunnel, altering its seismic response compared to the “free field conditions” case. The paper summarizes an attempt to identify and understand these interaction effects, focusing on the tunnel response. The problem is investigated in the transversal direction, by means of full dynamic time history analyses. Two structural configurations are studied and compared to the free field conditions case, consisting of one or two above ground structures, located over a circular tunnel. Above ground structures are modeled in a simplified way as equivalent single-degree of freedom oscillators, with proper mechanical properties. Several parameters that are significantly affecting the phenomenon are accounted for in this parametric study, namely the soil to tunnel relative flexibility, the tunnel dimensions, the tunnel burial depth and the soil properties and nonlinearities during shaking. Tunnels response characteristics are compared and discussed, in terms of acceleration, deformations and lining dynamic internal forces. Internal forces are also evaluated with analytical closed form solutions, commonly used in preliminary stages of design, and compared with the numerical predictions. The results indicate that the presence of the above ground structures may have a significant effect on the seismic response of the tunnel, especially when the latter is stiff and located in shallow depths.


      PubDate: 2015-01-16T05:56:34Z
       
  • Inelastic seismic spectra including a damage criterion: A stochastic
           approach
    • Abstract: Publication date: March 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 70
      Author(s): Rita Greco , Giuseppe Carlo Marano
      In this paper, a stochastic approach for obtaining damage-based inelastic seismic spectra is proposed. The Park and Ang damage model, which includes displacement ductility and hysteretic energy, is adopted to take into account the cumulative damage phenomenon in structural systems under strong ground motions. Differently from previous studies in this field, damage-based seismic spectra are obtained by means of peak theory of stochastic processes. The following stochastic inelastic seismic spectra are constructed and then analyzed: damage-based displacement and acceleration inelastic spectra, damage-based response modification factor spectra, damage-based yield strength demand spectra and damage-based inelastic displacement ratio spectra.


      PubDate: 2015-01-16T05:56:34Z
       
  • Mechanism and bounding of earthquake energy input to building structure on
           surface ground subjected to engineering bedrock motion
    • Abstract: Publication date: March 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 70
      Author(s): K. Kojima , K. Sakaguchi , I. Takewaki
      The mechanism of earthquake energy input to building structures is clarified by considering the surface ground amplification and soil–structure interaction. The earthquake input energies to superstructures, soil–foundation systems and total swaying–rocking system are obtained by taking the corresponding appropriate free bodies into account and defining the energy transfer functions. It has been made clear that, when the ground surface motion is white, the input energy to the swaying–rocking model is constant regardless of the soil property (input energy constant property). The upper bound of earthquake input energy to the swaying–rocking model is derived for the model including the surface ground amplification by taking full advantage of the above-mentioned input energy constant property and introducing the envelope function for the transfer function of the surface ground amplification. Extension of the theory to a general earthquake ground motion model at the engineering bedrock is also made by taking full advantage of the above-mentioned input energy constant property.


      PubDate: 2015-01-16T05:56:34Z
       
  • Seismic response of a pile-supported excavation on Santiago gravel
    • Abstract: Publication date: Available online 29 December 2014
      Source:Soil Dynamics and Earthquake Engineering
      Author(s): E. Sáez , G.S. Pardo , C. Ledezma
      Non-secant anchored piling support is one of the most frequent earth-retaining systems for temporary deep excavations in Santiago, Chile. The main advantages of using non-secant piling support are their relatively low cost and ease of installation. This system is particularly efficient on stiff soils with deep groundwater table, conditions usually found in Santiago. This paper presents the results of a numerical investigation aimed to study the characteristics of earthquake-induced lateral pressures on a recent pile-supported excavation 26m deep. The estimated static deformations of the piles were compared against some measurements performed during the excavation. The dynamic pressures, and their influence on the piles׳ internal forces, were evaluated using a synthetic Ricker wavelet in the numerical FE model. Two kinds of FE models were developed, an approximate 2D-plain strain model and a fully 3D model. The accuracy of the 2D model on predicting static and dynamic lateral pressures was also investigated.


      PubDate: 2015-01-16T05:56:34Z
       
  • Coherence of dispersed synthetic strong earthquake ground motion at small
           separation distances
    • Abstract: Publication date: March 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 70
      Author(s): Haiping Ding , Mihailo D. Trifunac , Maria I. Todorovska , Nebojša Orbović
      It is shown that the observed loss of coherency of synthetic strong motion on ground surface for separation distances less than about 100m can be described in terms of the dispersion of strong motion waves. Additional contributions to the loss of coherency from variations of material properties in the soil and from geometrical departures from perfectly flat ground surface and irregular layer geometries are not considered in this paper. It is also shown that the synthetic surface displacements over a large rectangular area (100×100m) on ground surface can be described well by a flat surface undergoing translations and rotations only, and with only minor departures from the plane flat surface.


      PubDate: 2015-01-16T05:56:34Z
       
  • Simulation of broadband seismic ground motions at dam canyons by using a
           deterministic numerical approach
    • Abstract: Publication date: Available online 31 December 2014
      Source:Soil Dynamics and Earthquake Engineering
      Author(s): Chun-Hui He , Jin-Ting Wang , Chu-Han Zhang , Feng Jin
      As a deterministic numerical approach for simulation of earthquake ground motions, the spectral element method (SEM) is applied to generate a broadband acceleration array for dam-canyons instead of the traditional empirical or stochastic methods. Specifically, the SEM analysis model with an extra fine mesh is used for the Pacoima Canyon to simulate the entire path starting from earthquake source rupture via the propagation medium to the local site. The source and the 3D earth model (velocity structure) are validated through the modeling of the Newhall earthquake on 28 October 2012 at a frequency of up to 8Hz. Subsequently, the San Fernando earthquake records on 13 January 2001 are further used to study the effects of propagation path in simulation. Finally, the spatially varying ground motions at the Pacoima Canyon are obtained for different source mechanisms. The results show that the source mechanism and the local site topography significantly affect the distribution of the peak accelerations along the canyon.
      Graphical abstract image

      PubDate: 2015-01-16T05:56:34Z
       
  • Discussion of the paper: “Recommendations for extension and
           re-calibration of an existing sand constitutive model taking into account
           varying non-plastic fines content”
    • Abstract: Publication date: March 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 70
      Author(s): Md Mizanur Rahman , S.R. Lo



      PubDate: 2015-01-16T05:56:34Z
       
  • Combined paraxial-consistent boundary conditions finite element model for
           simulating wave propagation in elastic half-space media
    • Abstract: Publication date: March 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 70
      Author(s): N. Hamdan , O. Laghrouche , P.K. Woodward , A. El-Kacimi
      In this paper, a finite element model of a soil island is coupled to both a consistent transmitting boundary and a paraxial boundary, which are then used to model the propagation of waves in semi-infinite elastic layered media. The formulation is carried out in the frequency domain while assuming plane strain conditions. It is known that a discrete model of this type, while providing excellent results for a wide range of physical parameters in the context of a half-space problem, may deteriorate rapidly at low frequencies of excitation. This is so because at low frequencies the various waves in the model eventually attain characteristic wavelengths which exceed the distance of the bottom boundary, which then causes that boundary to fail. Also, the paraxial boundaries themselves break down at very low frequencies. In this paper, this difficulty is overcome and the model׳s performance is improved upon dramatically by incorporating an artificial buffer layer sandwiched between the bottom of the soil medium and the underlying elastic half-space. Applications dealing with rigid foundations resting on homogenous or layered half-space media are shown to exhibit significant improvement. Following extensive simulations, clear guidelines are provided on the performance of the coupled model and an interpretation is given on the engineering significance of the findings. Finally, clear recommendations are provided for the practical use of the proposed modelling strategy.


      PubDate: 2015-01-16T05:56:34Z
       
  • Site condition evaluation using horizontal-to-vertical response spectral
           ratios of earthquakes in the NGA-West 2 and Japanese databases
    • Abstract: Publication date: December 2014
      Source:Soil Dynamics and Earthquake Engineering, Volume 67
      Author(s): Hadi Ghofrani , Gail M. Atkinson
      We evaluate the usefulness of the horizontal-to-vertical (H/V) response spectral ratio as a parameter to describe site response. In particular we compare its effectiveness with that of the time-averaged shear-wave velocity to 30m (V S30), and also look at how those two measures are correlated. The evaluation is performed considering two major compiled ground-motion databases, one being the international NGA-West 2 database, and the other being a comprehensive database from Japan. A uniform procedure is applied to pick peak frequency (f peak) and peak amplitude (A peak) from the averaged H/V response spectral ratio for each site in the database. The H/V peak parameters are then grouped by their behavior, and the relationship of these peak parameters to V S30 are investigated by region. We conclude that: (1) H/V offers at least as much site information as V S30; (2) H/V is of more descriptive value than V S30 for deep soil sites, having f peak≤1Hz; and (3) the averaged H/V response spectral ratio for a site peaks at a specific frequency which is related to the depth of deposit, and has a stable peak amplitude of ~0.45 log10 units, independent of the region. We conclude that H/V has significant advantages over V S30 as a site description variable, and note that it is in general easier (less expensive) to obtain.


      PubDate: 2015-01-16T05:56:34Z
       
  • Simplified multi-block constitutive model predicting earthquake-induced
           landslide triggering and displacement along slip surfaces of saturated
           sand
    • Abstract: Publication date: December 2014
      Source:Soil Dynamics and Earthquake Engineering, Volume 67
      Author(s): Constantine A. Stamatopoulos , Baofeng Di
      Slopes consisting of saturated sand have recently moved down-slope tens or hundreds of meters under the action of earthquakes. This paper presents a simplified but accurate method predicting the triggering and displacement of such landslides. For this purpose, a simplified constitutive model simulating soil response of saturated sands along slip surfaces is proposed and validated. Then, this constitutive model is coupled with the multi-block sliding system model to predict the triggering and displacement of such slides. The multi-block model considers a general mass sliding on a trajectory which consists of n linear segments. The steps needed to apply this method are described in detail. The method was applied successfully to predict the triggering, the motion and the final configuration of the well-documented (a) Higashi Takezawa, (b) Donghekou and (c) Nikawa earthquake-induced slides.


      PubDate: 2015-01-16T05:56:34Z
       
  • 1st Ishihara Lecture: An overview of the behavior of pile foundations in
           liquefiable and non-liquefiable soils during earthquake excitation
    • Abstract: Publication date: January 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 68
      Author(s): W.D. Liam Finn
      The seismic response of a pile foundation is usually analyzed by approximate methods in practice. These methods typically neglect one or more of the important factors that affect seismic response such as inertial interaction, kinematic interaction, seismic pore water pressures, soil nonlinearity, cross stiffness coupling and dynamic pile to pile interaction. A nonlinear 3-D analysis is used to show how all these factors affect pile response, to demonstrate some of the consequences of using various approximate methods and to provide a comprehensive overview of how pile foundations behave during earthquakes in liquefiable and non-liquefiable soils.


      PubDate: 2015-01-16T05:56:34Z
       
  • 2nd Ishihara Lecture: SPT- and CPT-based relationships for the residual
           shear strength of liquefied soils
    • Abstract: Publication date: January 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 68
      Author(s): I.M. Idriss , Ross W. Boulanger
      An evaluation of post-earthquake stability of earth embankments or slopes that contain, or are founded on, soils that may liquefy requires estimating the liquefied soil׳s residual shear strength, S r . Decisions regarding the need for expensive mitigation efforts, including ground improvement work, often hinge on the selected S r values. This paper presents recommended SPT- and CPT-based relationships for estimating the residual shear strength ratio, S r / σ ′ v o , of liquefied nonplastic soils in the field based on a review of prior case history studies, laboratory testing studies, and recent findings regarding void redistribution mechanisms. The recommended relationships provide guidance regarding the unavoidable task in practice of having to extrapolate beyond the available case history data. Limitations in the state of knowledge are discussed.


      PubDate: 2015-01-16T05:56:34Z
       
  • 3rd Ishihara Lecture: An investigation into why liquefaction charts work:
           A necessary step toward integrating the states of art and practice
    • Abstract: Publication date: January 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 68
      Author(s): Ricardo Dobry , Tarek Abdoun
      This paper is a systematic effort to clarify why field liquefaction charts based on Seed and Idriss׳ Simplified Procedure work so well. This is a necessary step toward integrating the states of the art (SOA) and practice (SOP) for evaluating liquefaction and its effects. The SOA relies mostly on laboratory measurements and correlations with void ratio and relative density of the sand. The SOP is based on field measurements of penetration resistance and shear wave velocity coupled with empirical or semi-empirical correlations. This gap slows down further progress in both SOP and SOA. The paper accomplishes its objective through: a literature review of relevant aspects of the SOA including factors influencing threshold shear strain and pore pressure buildup during cyclic strain-controlled tests; a discussion of factors influencing field penetration resistance and shear wave velocity; and a discussion of the meaning of the curves in the liquefaction charts separating liquefaction from no liquefaction, helped by recent full-scale and centrifuge results. It is concluded that the charts are curves of constant cyclic strain at the lower end (V s1<160m/s), with this strain being about 0.03–0.05% for earthquake magnitude, M w≈7. It is also concluded, in a more speculative way, that the curves at the upper end probably correspond to a variable increasing cyclic strain and K o, with this upper end controlled by overconsolidated and preshaken sands, and with cyclic strains needed to cause liquefaction being as high as 0.1–0.3%. These conclusions are validated by application to case histories corresponding to M w≈7, mostly in the San Francisco Bay Area of California during the 1989 Loma Prieta earthquake.


      PubDate: 2015-01-16T05:56:34Z
       
  • 4th Ishihara lecture: Soil–foundation–structure systems beyond
           conventional seismic failure thresholds
    • Abstract: Publication date: January 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 68
      Author(s): George Gazetas
      A new paradigm has now emerged in performance-based seismic design of soil–foundation–structure systems. Instead of imposing strict safety limits on forces and moments transmitted from the foundation onto the soil (aiming at avoiding pseudo-static failure), the new dynamic approach “invites” the creation of two simultaneous “failure” mechanisms: substantial foundation uplifting and ultimate-bearing-capacity slippage, while ensuring that peak and residual deformations are acceptable. The paper shows that allowing the foundation to work at such extreme conditions may not only lead to system collapse, but it would help protect (save) the structure from seismic damage. A potential price to pay: residual settlement and rotation, which could be abated with a number of foundation and soil improvements. Numerical studies and experiments demonstrate that the consequences of such daring foundation design would likely be quite beneficial to bridge piers, building frames, and simple frames retrofitted with a shear wall. It is shown that system collapse could be avoided even under seismic shaking far beyond the design ground motion. Three key phenomena are identified as the prime sources of the success; they are illustrated for a bridge–pier: (i) the constraining of the transmitted accelerations by the reduced ultimate moment capacity of the foundation, to levels of about one-half of those developing in a conventional design; (ii) the beneficial action of the static vertical load of the structure which pushes down to “re-center” the leaning (due to uplifting and soil yielding) footing, instead of further distressing the plastic hinge of the column of the conventional design; and (iii) the substantial increase of the fundamental natural period of the system as uplifting takes place, which brings the structure beyond the significant period range of a ground motion, and hence leads to the abatement of its severe shaking.


      PubDate: 2015-01-16T05:56:34Z
       
  • Breach of a tailings dam in the 2011 earthquake in Japan
    • Abstract: Publication date: January 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 68
      Author(s): Kenji Ishihara , Kennosuke Ueno , Seishi Yamada , Susumu Yasuda , Takeshi Yoneoka
      The eastern region of the northern part of Japanese mainland has been known historically as an area of mines producing gold and silver. When the extraordinarily strong earthquake rocked the eastern part of the Japanese mainland on March 11, 2011, there were more than 20 old and new dams retaining tailings from many mines. Out of these, three dams suffered breach due to liquefaction of tailings materials and released a large amount of slime, bringing about damage to farmlands and houses downstream. Of particular interest was Kayakari dam at Ohya mine that failed and Takasega-mori dam in its vicinity that did not, although they were equally subjected to strong shaking. In this paper features of these two dams in the design and construction, and damage or non-damage during the earthquake will be described, together with the geotechnical investigations and some analyses that were conducted after the earthquake.


      PubDate: 2015-01-16T05:56:34Z
       
  • Editorial Board / Aims and Scope
    • Abstract: Publication date: January 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 68




      PubDate: 2015-01-16T05:56:34Z
       
  • Preamble
    • Abstract: Publication date: January 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 68
      Author(s): Kyriazis Pitilakis , Ahmed Elgamal



      PubDate: 2015-01-16T05:56:34Z
       
  • Seismic vulnerability assessment based on typological characteristics. The
           first level procedure “SAVE”
    • Abstract: Publication date: February 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 69
      Author(s): G. Zuccaro , F. Cacace
      In this paper a procedure is described for quick seismic vulnerability assessment according to the EMS 98 classification. The criteria adopted by Ems 98 to assign the typological classes are mainly based on the vertical structure type. The proposed methodology aims to reduce the uncertainty in the class assessment using a set of parameters, related to typological features, that are identified as modifiers of the vulnerability level. The paper shows how the weight of each of these parameters is evaluated through the analysis of the seismic damages recorded during past earthquakes. A synthetic damage parameter is then defined in order to compare the seismic response of different sets of buildings under the same seismic intensity. Finally, the vulnerability assessment obtained on a set of buildings by the application of the methodology is compared with expert evaluations derived from the direct inspections on buildings.


      PubDate: 2015-01-16T05:56:34Z
       
  • Field experiment and numerical study on active vibration isolation by
           horizontal blocks in layered ground under vertical loading
    • Abstract: Publication date: February 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 69
      Author(s): Guangyun Gao , Ning Li , Xiaoqiang Gu
      In this paper, a series of field experiments were carried out to investigate the active vibration isolation for a surface foundation using horizontal wave impedance block (WIB) in a multilayered ground under vertical excitations. The velocity amplitude of ground vibration was measured and the root-mean-square (RMS) velocity is used to evaluate the vibration mitigation effect of the WIB. The influences of the size, the embedded depth and the shear modulus of the WIB on the vibration mitigation were also systematically examined under different loading conditions. The experimental results convincingly indicate that WIB is effective to reduce the ground vibration, especially at high excitation frequencies. The vibration mitigation effect of the WIB would be improved when its size and shear modulus increase or the embedded depth decreases. The results also showed that the WIB may amplify rather than reduce the ground vibration when its shear modulus is smaller or the embedded depth is larger than a threshold value. Meanwhile, an improved 3D semi-analytical boundary element method (BEM) combined with a thin layer method (TLM) was proposed to account for the rectangular shape of the used WIB and the laminated characteristics of the actual ground condition in analyzing the vibration mitigation of machine foundations. Comparisons between the field experiments and the numerical analyses were also made to validate the proposed BEM.


      PubDate: 2015-01-16T05:56:34Z
       
  • Investigation on the stochastic simulation of strong ground motions for
           Bucharest area
    • Abstract: Publication date: February 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 69
      Author(s): Florin Pavel
      This short article evaluates the stochastic method of ground motion simulation for Bucharest area using both the single-corner frequency model and recently introduced double-corner frequency models. A dedicated Q model is derived using ground motions obtained during the largest Vrancea earthquakes from the past 30 years. The simulated ground motions are tested against the observed data from the Vrancea earthquakes of August 1986 and May 1990. Moreover, the observed data are also compared against simulations obtained using the Q model derived by Oth et al. (2008). Finally, the results of the simulations show that the derived Q model is better suited for larger magnitude events, while the Q model of Oth et al. (2008) provides better results for smaller earthquakes.


      PubDate: 2015-01-16T05:56:34Z
       
  • Passive and hybrid mitigation of potential near-fault inner pounding of a
           self-braking seismic isolator
    • Abstract: Publication date: February 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 69
      Author(s): Mohammed Ismail , José Rodellar , Francesc Pozo
      A seismic isolated structure is usually a long-period structural system, which may encounter a low-frequency resonance problem when subjected to a near-fault earthquake that usually has a long-period pulse-like waveform. This long-period wave component may result in an enlargement of the base displacement and a decrease of the isolation efficiency. To overcome this problem, a rolling-based seismic isolator, referred to as roll-n-cage (RNC) isolator, has been recently proposed. The RNC isolator has a built-in buffer (braking) mechanism that limits the peak isolator displacements under severe earthquakes and prevents adjacent structural pounding. This paper addresses the problem of passive and hybrid mitigation of the potential inner pounding of the self-braking RNC isolator under near-fault earthquakes. Numerical results show that the RNC isolator can intrinsically limit the isolator displacements under near-fault earthquakes with less severe inner pounding using additional hysteretic damping and active control forces.


      PubDate: 2015-01-16T05:56:34Z
       
  • Prediction of railway ground vibrations: Accuracy of a coupled lumped mass
           model for representing the track/soil interaction
    • Abstract: Publication date: February 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 69
      Author(s): G. Kouroussis , O. Verlinden
      Recent advances in railway-induced ground vibrations showed that the track/soil interaction plays an important role in the low frequency range. This paper contributes to the numerical analysis of train/track/foundation dynamics by presenting the accuracy of a coupled lumped mass (CLM) model devoted to the railway foundations and to the track/soil coupling. Following a summary of the background and the advantages of the CLM model, the coupling strategy is quantified through two application cases. Firstly, the dynamic track deflection is calculated for different railway lines considering various degrees of complexities of foundations. Then, the foundation responses are compared depending on whether detailed coupling is introduced or not. The benefit of the proposed model is emphasized by presenting free-field ground vibration responses generated by a tram and a high-speed train, obtained by a revisited two-step prediction model developed by the authors.


      PubDate: 2015-01-16T05:56:34Z
       
  • Comparison of 1D linear, equivalent-linear, and nonlinear site response
           models at six KiK-net validation sites
    • Abstract: Publication date: February 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 69
      Author(s): James Kaklamanos , Laurie G. Baise , Eric M. Thompson , Luis Dorfmann
      Vertical seismometer arrays represent a unique interaction between observed and predicted ground motions, and they are especially helpful for validating and comparing site response models. In this study, we perform comprehensive linear, equivalent-linear, and nonlinear site response analyses of 191 ground motions recorded at six validation sites in the Kiban–Kyoshin network (KiK-net) of vertical seismometer arrays in Japan. These sites, which span a range of geologic conditions, are selected because they meet the basic assumptions of one-dimensional (1D) wave propagation, and are therefore ideal for validating and calibrating 1D nonlinear soil models. We employ the equivalent-linear site response program SHAKE, the nonlinear site response program DEEPSOIL, and a nonlinear site response overlay model within the general finite element program Abaqus/Explicit. Using the results from this broad range of ground motions, we quantify the uncertainties of the alternative site response models, measure the strain levels at which the models break down, and provide general recommendations for performing site response analyses. Specifically, we find that at peak shear strains from 0.01% to 0.1%, linear site response models fail to accurately predict short-period ground motions; equivalent-linear and nonlinear models offer a significant improvement at strains beyond this level, with nonlinear models exhibiting a slight improvement over equivalent-linear models at strains greater than approximately 0.05%.


      PubDate: 2015-01-16T05:56:34Z
       
  • Influence of pile inclination angle on the dynamic properties and seismic
           response of piled structures
    • Abstract: Publication date: February 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 69
      Author(s): Cristina Medina , Luis A. Padrón , Juan J. Aznárez , Orlando Maeso
      This paper aims to contribute to clarify whether the use of battered piles has a positive or a negative influence on the dynamic response of deep foundations and superstructures. For this purpose, the dynamic response of slender and non-slender structures supported on several configurations of 2×2 and 3×3 pile groups including battered elements is obtained through a procedure based on a substructuring model assuming a linear elastic response and taking soil–structure interaction into account. Results are expressed in terms of flexible-base period and maximum shear force at the base of the structure. Moreover, modified response spectra considering soil–structure interaction effects are provided for different rake angles. It is shown that an increment of the rake angle can result in beneficial or detrimental effects depending on the structural slenderness ratio.
      Graphical abstract image Highlights

      PubDate: 2015-01-16T05:56:34Z
       
  • Response of circular flexible foundations subjected to horizontal and
           rocking motions
    • Abstract: Publication date: February 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 69
      Author(s): Shi-Shuenn Chen , Jr-Gang Hou
      A methodology using modal analysis is developed to evaluate dynamic vertical displacements of a circular flexible foundation resting on soil media subjected to horizontal and rocking motions. The influence of the soil reaction forces on the foundation is considered by introducing modal impedance functions, which can be determined by an efficient procedure with ring elements. The displacements of the foundation can then be easily solved by modal superposition. Parametric studies for modal responses of the flexible foundation indicate that the coupled response of the foundation is significantly influenced by relative stiffness among the foundation and the soil medium, vibration frequency range, foundation mass, and boundary contact conditions. The welded boundary condition should be considered to predict the coupling response while the relaxed boundary condition may be used to predict approximately the vertical displacements. As a foundation with a relative stiffness ratio more than three, it is found that the foundation can be considered as rigid to calculate coupling displacements. For a slightly flexible foundation, considerations of three modes are sufficient enough to obtain accurate foundation responses. Moreover, at low frequencies, the coupling effect due to higher mode can be neglected.


      PubDate: 2015-01-16T05:56:34Z
       
  • Dynamic responses of a saturated poroelastic half-space generated by a
           moving truck on the uneven pavement
    • Abstract: Publication date: February 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 69
      Author(s): Yuanqiang Cai , Yao Chen , Zhigang Cao , Honglei Sun , Lin Guo
      A truck–pavement–ground coupling model was established to study the dynamic responses of a saturated poroelastic half-space generated by a moving heavy truck on the uneven pavement. The ground was simulated as a fully saturated poroelastic half-space governed by Biot’s theory. The overlying pavement was simplified as a Kirchhoff thin plate. With the assumption of a sinusoidal pavement surface, the dynamic wheel–pavement force was obtained through a linear Hertizian contact model. The numerical results showed that this dynamic load could make considerable contributions to the stress and excess pore water pressure responses in the ground. Furthermore, the effective stress path of the soil unit beneath the pavement caused by the moving truck was firstly calculated and presented. It was found that the differences between the total stress path and the effective stress path became significant as the truck speed increased, thus the effective stress path was more suitable than total stress path to reflect the stress history of soil elements in the saturated ground during the passage of high-speed traffics.


      PubDate: 2015-01-16T05:56:34Z
       
  • Three-dimensional poro-elasto-plastic model for wave-induced seabed
           response around submarine pipeline
    • Abstract: Publication date: February 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 69
      Author(s): X.L. Zhang , C.S. Xu , Y. Han
      The evaluation of the wave-induced excess pore pressure around a buried pipeline is particularly important for pipeline engineers involved in the design of offshore pipelines. Existing models for the wave-induced seabed response around submarine pipeline have been limited to poro-elastic soil behavior and de-coupled oscillatory and residual mechanisms for the rise in excess pore water pressure. To overcome the shortcoming of the existing models, in this study a three-dimensional poro-elasto-plastic soil model with submarine pipeline is established, in which both oscillatory and residual mechanisms can be simulated simultaneously. With the proposed model, a parametric study is conducted to investigate the relative differences of the predictions of the wave-induced pore pressure with poro-elasto-plastic model. Based on numerical examples, it can be concluded that the poro-elasto-plastic behaviors of soil have more significant influence on wave-induced pore pressure of seabed around submarine pipeline. As the seabed depth increases, the normalized pore pressures decrease rapidly at the upper part of seabed, and then change slightly at the lower part of the seabed. Soil permeability and wave period have obvious influence on the wave-induced normalized pore pressure.


      PubDate: 2015-01-16T05:56:34Z
       
  • Correlation between strong motion durations and damage measures of
           concrete gravity dams
    • Abstract: Publication date: February 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 69
      Author(s): Gaohui Wang , Sherong Zhang , Chuangbing Zhou , Wenbo lu
      Strong motion duration affects the cumulative damage of structures significantly. There are more than 30 different definitions of strong motion duration. This study describes numerically, the interdependency between several different definitions of strong motion duration and structural accumulated damage indices, and the aim is to determine the definitions of strong motion duration that exhibit the strongest influence on structural damages. For this purpose, 20 as-recorded accelerograms with a wide range of durations, which are modified to match a 5% damped target spectrum, are considered in this study, and several different definitions of strong motion duration, such as significant duration, bracketed duration and uniform duration are proposed for measuring these durations. On the other hand, nonlinear seismic analyses of concrete gravity dams subjected to earthquake motions with different strong motion durations are conducted according to the Concrete Damaged Plasticity (CDP) model including the strain hardening or softening behavior. Peak displacement, local damage index, global damage index and damage energy dissipation are established for characterizing the influence of strong motion duration on the dynamic response of concrete gravity dams. The degree of the interrelationship between strong motion durations and damage measures is provided by correlation coefficients. Comparison of the correlation between the different durations of the ground motion and different damage measures reveals that strong motion durations calculated from different definitions have no significant influence on damage measure based on the peak displacement response of the dam, but are positively correlated to the accumulated damage measures such as the local damage index, global damage index and damage energy dissipation for events with similar response spectrum.


      PubDate: 2015-01-16T05:56:34Z
       
  • Simplified method for generating slope seismic deformation hazard curve
    • Abstract: Publication date: February 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 69
      Author(s): Zeljko Zugic , Vlatko Sesov , Mihail Garevski , Mirjana Vukićević , Sanja Jockovic
      A simplified method for generating slope deformation hazard curve that takes into account the variations of input parameters is presented in this paper. The main assumption in the new approach is that the occurrence of peak slope deformation is Poisson׳s process. The procedure is based on logic tree analysis, commercial software and routines programmed by the authors for generating sets of input files, and forming slope performance curve. The methodology was applied to a real landslide in order to demonstrate the advantages and limitations of the proposed approach. The results of the analysis showed the influence of the certain input factors on sliding displacement as well as the advantages of employing continuum mechanics approach.


      PubDate: 2015-01-16T05:56:34Z
       
  • Stress attractors predicted by a high-cycle accumulation model confirmed
           by undrained cyclic triaxial tests
    • Abstract: Publication date: February 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 69
      Author(s): T. Wichtmann , T. Triantafyllidis
      Depending on the boundary conditions a high-cyclic loading (=large number of cycles N ≥ 10 3 , small strain amplitudes ε ampl ≤ 10 − 3 ) may either lead to strain accumulation or stress relaxation in the soil. This paper concentrates on stress relaxation. For a cyclic loading applied under undrained triaxial conditions, the high-cycle accumulation (HCA) model of Niemunis et al. [23] predicts a relaxation of average effective stress until a stress ratio η av = q av / p av = M cc (triaxial compression) or M ec (extension) is reached. M cc and M ec are very similar to the critical stress ratios M c and M e known from monotonic shear tests. The average effective stresses finally reached after a sufficiently large number of cycles are called “stress attractors” herein. A zero effective stress state (liquefaction, p av = q av =0) is obtained as a special case of a stress attractor. However, up to now the stress attractors predicted by the HCA model were based on the data from drained cyclic tests only. In the present study they have been approximately confirmed by stress relaxation experiments, i.e. undrained cyclic triaxial tests with stress or strain control. These tests have been performed on a fine sand, varying the initial values of density, mean pressure and stress ratio as well as the stress or strain amplitude.


      PubDate: 2015-01-16T05:56:34Z
       
  • Displacement-based seismic design of hysteretic damped braces for
           retrofitting in-elevation irregular r.c. framed structures
    • Abstract: Publication date: February 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 69
      Author(s): Fabio Mazza , Mirko Mazza , Alfonso Vulcano
      A displacement-based design procedure is proposed for proportioning hysteretic damped braces (HYDBs) in order to attain, for a specific level of seismic intensity, a designated performance level of a reinforced concrete (r.c.) in-elevation irregular framed building which has to be retrofitted. To check the effectiveness and reliability of the design procedure, a numerical investigation is carried out with reference to a six-storey r.c. framed building, which, originally designed according to an old Italian seismic code (1996) for a medium-risk zone, has to be retrofitted by inserting of HYDBs to attain performance levels imposed by the current Italian code (NTC08) in a high-risk zone. To simulate a vertical irregularity, a change of use of the first two floors, from residential to office, is also supposed; moreover, masonry infill walls, regularly distributed along the perimeter, are substituted with glass windows on these floors. Nonlinear dynamic analyses of unbraced (UF), infilled (IF) and damped braced infilled (DBIF) frames are carried out considering sets of artificially generated and real ground motions, whose response spectra match those adopted by NTC08 for different performance levels. To this end, r.c. frame members are idealized by a two-component model, assuming a bilinear moment–curvature law whose ultimate bending moment depends on the axial load, while the response of an HYDB is idealized by a bilinear law, to prevent buckling. Finally, masonry infills are represented as equivalent diagonal struts, reacting only in compression, with an elastic–brittle linear law.


      PubDate: 2015-01-16T05:56:34Z
       
  • On the influence of a non-cohesive fines content on small strain
           stiffness, modulus degradation and damping of quartz sand
    • Abstract: Publication date: February 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 69
      Author(s): T. Wichtmann , M.A. Navarrete Hernández , T. Triantafyllidis
      The influence of a non-cohesive fines content on small-strain shear modulus G max , small-strain constrained elastic modulus M max , shear modulus degradation G ( γ ) / G max , damping ratio D ( γ ) and threshold shear strain amplitudes γ tl and γ tv has been studied in approx. 130 resonant column (RC) tests with additional P-wave measurements by means of piezoelectric elements. Specially mixed continuous grain size distribution curves of a quartz sand with varying fines contents ( 0 ≤ FC ≤ 20 % , defined as the mass percentage of grains with size d < 0.063 mm according to DIN standard code) and uniformity coefficients ( 1.5 ≤ C u ≤ 50 ) have been tested at different relative densities and pressures. A significant decrease of G max and M max with increasing fines content was observed, while the modulus degradation curves G ( γ ) / G max were found rather independent of FC. A pressure-dependent decrease of the damping ratio and a slight increase of the threshold shear strain amplitudes γ tl and γ tv with fines content were measured. Extensions of several empirical equations for G max , M max , G ( γ ) / G max and D ( γ ) considering the influence of the fines content are proposed in the paper.


      PubDate: 2015-01-16T05:56:34Z
       
  • Scattering and intrinsic attenuation in Cairo metropolitan area using
           genetic algorithm
    • Abstract: Publication date: February 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 69
      Author(s): Mohamed F. Abdelwahed , Ali K. Abdel-Fattah
      A total number of 46 local earthquakes (2.0≤ML≤4.0) recorded in the period 2000–2011 by the Egyptian seismographic network (ENSN) were used to estimate the total (Q t −1), intrinsic (Q i −1) and scattering attenuation (Q sc −1) in Cairo metropolitan area, Egypt. The multiple lapse time window analysis (MLTWA) under the assumption of multiple isotropic scattering with uniform distribution of scatters was firstly applied to estimate the pair of L e −1, the extinction length inverse, and B 0, the seismic albedo, in the frequency range 3–24Hz. To take into account the effect of a depth-dependent earth model, the obtained values of B 0 and L e −1 were corrected for an earth structure characterized by a transparent upper mantle and a heterogeneous crust. The estimated values of Q t −1, Q sc −1 and Q i −1 exhibited frequency dependences. The average frequency-dependent relationships of attenuation characteristics estimated for the region are found to be: Q t −1=(0.015±0.008)f (−1.02±0.02), Q sc −1=(0.006±0.001)f (−1.01±0.02), and Q i −1=(0.009±0.008)f (−1.03±0.02); showing a predominance of intrinsic absorption over scattering attenuation. This finding implies that the pore-fluid contents may have great effect on the attenuation mechanism in the upper crust where the River Nile is passing through the study area. The obtained results are comparable with those obtained in other tectonic regions.


      PubDate: 2015-01-16T05:56:34Z
       
  • Stochastic analysis of ground response using non-recursive algorithm
    • Abstract: Publication date: February 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 69
      Author(s): A. Johari , M. Momeni
      During an earthquake, the amplitudes of seismic wave may amplify significantly as it propagates through the soil layers near the ground surface. Analysis of site amplification potential is strongly influenced by the uncertainty associated to the definition of soil thickness and its properties. In this paper, the non-recursive algorithm is used in linear and nonlinear Hybrid Frequency Time Domain (HFTD) approaches for stochastic analysis of site amplification. The non-recursive algorithm causes time reduction of analysis that is the essential base of stochastic analysis. The selected soil stochastic parameters are shear wave velocity, density, damping and thickness. The results of sensitivity analysis also show that the damping ratio is the most effective parameter in PGA at ground surface. The stochastic peak ground acceleration, response spectrum and amplification factor at the ground surface are determined by the two approaches for four sites with different average shear wave velocities. Comparison of the results shows that the nonlinear HFTD approach predicts closer response to real recorded data with respect to linear HFTD.


      PubDate: 2015-01-16T05:56:34Z
       
  • Assessing the impact of ground-motion variability and uncertainty on
           empirical fragility curves
    • Abstract: Publication date: February 2015
      Source:Soil Dynamics and Earthquake Engineering, Volume 69
      Author(s): Ioanna Ioannou , John Douglas , Tiziana Rossetto
      Empirical fragility curves, constructed from databases of thousands of building-damage observations, are commonly used for earthquake risk assessments, particularly in Europe and Japan, where building stocks are often difficult to model analytically (e.g. old masonry structures or timber dwellings). Curves from different studies, however, display considerable differences, which lead to high uncertainty in the assessed seismic risk. One potential reason for this dispersion is the almost universal neglect of the spatial variability in ground motions and the epistemic uncertainty in ground-motion prediction. In this paper, databases of building damage are simulated using ground-motion fields that take account of spatial variability and a known fragility curve. These databases are then inverted, applying a standard approach for the derivation of empirical fragility curves, and the difference with the known curve is studied. A parametric analysis is conducted to investigate the impact of various assumptions on the results. By this approach, it is concluded that ground-motion variability leads to flatter fragility curves and that the epistemic uncertainty in the ground-motion prediction equation used can have a dramatic impact on the derived curves. Without dense ground-motion recording networks in the epicentral area empirical curves will remain highly uncertain. Moreover, the use of aggregated damage observations appears to substantially increase uncertainty in the empirical fragility assessment. In contrast, the use of limited randomly-chosen un-aggregated samples in the affected area can result in good predictions of fragility.


      PubDate: 2014-12-08T15:45:21Z
       
 
 
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