Soil Dynamics and Earthquake Engineering [SJR: 1.482] [H-I: 45] [7 followers] Follow Hybrid journal (It can contain Open Access articles) ISSN (Print) 0267-7261 Published by Elsevier [2801 journals] |
- Vibration control by damped braces of fire-damaged steel structures
subjected to wind and seismic loads- Abstract: Publication date: April 2016
Source:Soil Dynamics and Earthquake Engineering, Volume 83
Author(s): Fabio Mazza, Marco Fiore
The aim of the present work is to evaluate the effectiveness of viscoelastic-damped braces (VEDBs) to improve the wind and earthquake responses of fire-damaged steel framed buildings, where a significant reduction of stiffness and strength properties of the structural elements following exposure to fire is highlighted. To this end, a ten-storey steel office building, designed for a low-risk zone under the former Italian seismic code and in line with Eurocodes 1 and 3, is considered as test structure. The dynamic response of the test structure in a no fire situation is compared with what would happen in the event of three fire scenarios, on the assumption that the fire compartment with a uniform temperature is confined to the area of the first (i.e. F1), fifth (i.e. F5) and tenth (i.e. F10) level, with the parametric temperature–time fire curve evaluated in line with Eurocode 1. Two retrofitting structural solutions are examined to upgrade the fire damaged test structures, by inserting diagonal steel braces with or without viscoelastic dampers. Frame members are idealized by a bilinear model, which allows the simulation of the nonlinear behavior under seismic loads, while an elastic linear law is considered for diagonal braces. Finally, viscoelastic dampers are idealized by means of a frequency-dependent model.
PubDate: 2016-02-01T11:44:47Z
- Abstract: Publication date: April 2016
- Seismic ground motion amplification pattern induced by a subway tunnel:
Shaking table testing and numerical simulation- Abstract: Publication date: April 2016
Source:Soil Dynamics and Earthquake Engineering, Volume 83
Author(s): Masoud Rabeti Moghadam, Mohammad Hassan Baziar
A series of 1g shaking table tests, followed by the numerical simulations, is performed to investigate the effect of a circular subway tunnel on the ground motion amplification pattern. Effects of various parameters, including shear wave velocity of soil, frequency content of input motion, flexibility ratio and tunnel depth on the amplification pattern is investigated. Experimental study revealed that the tunnel did not affect free field response at dimensionless period greater than 10. Subsequent parametric study demonstrated that the amount of amplifications were mainly controlled by dimensionless period, dimensionless depth and flexibility ratio. Tunnel effect on the amplification pattern is more prominent for dimensionless period between 3 to 10, flexibility ratio greater than 1 and dimensionless depth less than 3. The study revealed that subway tunnel influences the seismic response of low period buildings, constructed above the tunnel.
PubDate: 2016-02-01T11:44:47Z
- Abstract: Publication date: April 2016
- Investigation on the accuracy of the N2 method and the equivalent
linearization procedure for different hysteretic models- Abstract: Publication date: April 2016
Source:Soil Dynamics and Earthquake Engineering, Volume 83
Author(s): Claudio Amadio, Giovanni Rinaldin, Massimo Fragiacomo
In this paper, an extensive parametric study was carried out to evaluate the dynamic response of single degree of freedom (SDOF) systems with elasto-plastic and flag-shape hysteretic behaviour for three different dissipation capacities. Three sets of natural accelerograms were used, each one composed by at least 7 records which are on average spectrum-consistent in pseudo-acceleration, spectral displacement or both of them. All sets were also employed to draw the inelastic spectra for different ductility values. Such rigorous spectra were then compared with the approximated curves calculated using the N2 method and the Equivalent Linearization Procedure (ELP) based on the use of overdamped elastic spectra. The analyses demonstrate a general accuracy of the N2 method, which is mostly based on the ductility of the system, even for the hysteretic behaviour characterised by reduced energy dissipation. Larger discrepancies were found for systems with lower damping ratios and reduced fundamental periods. The ELP, which mainly depends upon the dissipated energy, led instead to overall slightly larger discrepancies than the N2 method, particularly for not dissipative and ductile systems, whereas the approximation is generally acceptable for elasto-plastic systems.
PubDate: 2016-02-01T11:44:47Z
- Abstract: Publication date: April 2016
- Identification of dynamic soil properties through shaking table tests on a
large saturated sand specimen in a laminar shear box- Abstract: Publication date: April 2016
Source:Soil Dynamics and Earthquake Engineering, Volume 83
Author(s): Chi-Chin Tsai, Wei-Chun Lin, Jiunn-Shyang Chiou
Many laminar shear boxes have recently been developed into sliding-frame containers that can reproduce 1D ground-response boundary conditions. The measured responses of such large specimens can be utilized to back-calculate soil properties. This study investigates how the boundary effect in large specimens affects the identified soil properties through shaking table tests on a soil-filled large laminar box conducted at the National Center for Research on Earthquake Engineering in Taiwan. The tested soil-box system is unique because only 80% of the container is filled with soil. This system can be regarded as a two-layer system: an empty top and soil-filled bottom. The dynamic properties of this two-layer system are identified through various approaches, including theoretical solutions of wave propagation, free vibration, and nonparametric stress–strain analyzes. Therefore, the coupling effect of the box and soil can be evaluated. Results show that, compared with the two-layer system considering the influence of the box, the conventional approach with a single-layer system slightly underestimates shear wave velocity but obtains the same damping ratio of the soil layer. In addition, the identified modulus reduction and damping curves in the two-layer system are consistent with those obtained in a laboratory test on a small specimen. Furthermore, based on detailed acceleration measurements along different depths of soil, a piecewise profile of shear wave velocity is built. The identified shear wave velocity increases with depth, which is not uniform and differs from the constant velocity typically assumed for the specimen.
PubDate: 2016-02-01T11:44:47Z
- Abstract: Publication date: April 2016
- InterPACIFIC project: Comparison of invasive and non-invasive methods for
seismic site characterization. Part II: Inter-comparison between
surface-wave and borehole methods- Abstract: Publication date: Available online 28 January 2016
Source:Soil Dynamics and Earthquake Engineering
Author(s): F. Garofalo, S. Foti, F. Hollender, P.Y. Bard, C. Cornou, B.R. Cox, A. Dechamp, M. Ohrnberger, V. Perron, D. Sicilia, D. Teague, C. Vergniault
The InterPACIFIC project was aimed at assessing the reliability, resolution, and variability of geophysical methods in estimating the shear-wave velocity profile for seismic ground response analyses. Three different subsoil conditions, which can be broadly defined as soft-soil, stiff-soil, and hard-rock, were investigated. At each site, several participants performed and interpreted invasive measurements of shear wave velocity (Vs) and compression wave velocity (Vp) in the same boreholes. Additionally, participants in the project analysed a common surface-wave dataset using their preferred strategies for processing and inversion to obtain Vs profiles. The most significant difference between the invasive borehole methods and non-invasive surface wave methods is related to resolution of thin layers and abrupt contrasts, which is inherently better for invasive methods. However, similar variability is observed in the estimated invasive and non-invasive Vs profiles, underscoring the need to account for such uncertainty in site response studies. V S,30 estimates are comparable between invasive and non-invasive methods, confirming that the higher resolution provided by invasive methods is quite irrelevant for computing this parameter.
PubDate: 2016-01-28T08:15:42Z
- Abstract: Publication date: Available online 28 January 2016
- Earth pressure of layered soil on retaining structures
- Abstract: Publication date: April 2016
Source:Soil Dynamics and Earthquake Engineering, Volume 83
Author(s): Shi Han, Jinxing Gong, Yanqing Zhang
Earth pressure evaluation of retaining structure is not a new thing in geotechnical engineering. Up to date, many analytical and numerical approaches have been developed, but limitations of these available approaches are obvious for the application in some situations. The main objective of this paper is to develop a method to predict the earthquake pressure of retaining structures based on wedge method with as few limitations as possible. The developed method is suitable for retaining structures in the case of layered backfill with zero slope angle from horizontal level and with curved failure surface. To generate a curved failure surface, the sliding wedge is divided into many thin-layer micro-elements and the equilibrium equations of each micro-element are established. In the case of seismic analysis, the seismic actions are considered as static inertia forces on layered micro-elements. The shape of failure surface is determined by using available optimization method. Effects of the friction angle between wall and backfill soil on the distribution of earth pressure and the shape of failure surface were investigated, and earth pressures estimated based on curved and linear failure surfaces were compared. Analysis results indicate that the potential failure surface in the backfill soil depends on the friction angle between wall and backfill soil. For small friction angle, the failure surface tends to be planar. The active earth pressures corresponding to curved and planar failure surfaces are almost identical, but the discrepancies between the results of the two failure surface are large and increase with the increase of wall friction. Comparisons between results of the proposed method and those of the available methods as well as experimental results were conducted. Comparison result indicates that the merits of the proposed method are obvious.
PubDate: 2016-01-28T08:15:42Z
- Abstract: Publication date: April 2016
- InterPACIFIC project: Comparison of invasive and non-invasive methods for
seismic site characterization. Part I: Intra-comparison of surface wave
methods- Abstract: Publication date: Available online 21 January 2016
Source:Soil Dynamics and Earthquake Engineering
Author(s): F. Garofalo, S. Foti, F. Hollender, P.Y. Bard, C. Cornou, B.R. Cox, M. Ohrnberger, D. Sicilia, M. Asten, G. Di Giulio, T. Forbriger, B. Guillier, K. Hayashi, A. Martin, S. Matsushima, D. Mercerat, V. Poggi, H. Yamanaka
The main scope of the InterPACIFIC (Intercomparison of methods for site parameter and velocity profile characterization) project is to assess the reliability of in-hole and surface-wave methods, used for estimating shear wave velocity. Three test-sites with different subsurface conditions were chosen: a soft soil, a stiff soil and a rock outcrop. This paper reports the surface-wave methods results. Specifically 14 teams of expert users analysed the same experimental surface-wave datasets, consisting of both passive and active data. Each team adopted their own strategy to retrieve the dispersion curve and the shear-wave velocity profile at each site. Despite different approaches, the dispersion curves are quite in agreement with each other. Conversely, the shear-wave velocity profiles show a certain variability that increases in correspondence of major stratigraphic interfaces. This larger variability is mainly due to non-uniqueness of the solution and lateral variability. As expected, the observed variability in V S,30 estimates is small, as solution non-uniqueness plays a limited role.
PubDate: 2016-01-22T08:06:46Z
- Abstract: Publication date: Available online 21 January 2016
- Closed form solution of Eigen frequency of monopile supported offshore
wind turbines in deeper waters incorporating stiffness of substructure and
SSI- Abstract: Publication date: April 2016
Source:Soil Dynamics and Earthquake Engineering, Volume 83
Author(s): Laszlo Arany, S. Bhattacharya, John H.G. Macdonald, S. John Hogan
Offshore wind turbines (OWTs) are dynamically loaded structures and therefore the estimation of the natural frequency is an important design calculation to avoid resonance and resonance related effects (such as fatigue). Monopiles are currently the most used foundation type and are also being considered in deeper waters (>30m) where a stiff transition piece will join the monopile and the tapered tall tower. While rather computationally expensive, high fidelity finite element analysis can be carried to find the Eigen solutions of the whole system considering soil–structure interaction; a quick hand calculation method is often convenient during the design optimisation stage or conceptual design stage. This paper proposes a simplified methodology to obtain the first natural frequency of the whole system using only limited data on the WTG (Wind Turbine Generator), tower dimensions, monopile dimensions and the ground. The most uncertain component is the ground and is characterised by two parameters: type of ground profile (i.e. soil stiffness variation with depth) and the soil stiffness at one monopile depth below mudline. In this framework, the fixed base natural frequency of the wind turbine is first calculated and is then multiplied by two non-dimensional factors to account for the foundation flexibility (i.e. the effect of soil–structure interaction). The theoretical background behind the model is the Euler–Bernoulli and Timoshenko beam theories where the foundation is idealised by three coupled springs (lateral, rocking and cross-coupling). 10 wind turbines founded in different ground conditions from 10 different wind farms in Europe (e.g. Walney, Gunfleet sand, Burbo Bank, Belwind, Barrow, Kentish flat, Blyth, Lely, Thanet Sand, Irene Vorrink) have been analysed and the results compared with the measured natural frequencies. The results show good accuracy (errors below 3.5%). A step by step sample calculation is also shown for practical use of the proposed methodology.
PubDate: 2016-01-22T08:06:46Z
- Abstract: Publication date: April 2016
- Evaluation of underground tunnel response to reverse fault rupture using
numerical approach- Abstract: Publication date: April 2016
Source:Soil Dynamics and Earthquake Engineering, Volume 83
Author(s): Mohammad Hassan Baziar, Ali Nabizadeh, Ronak Mehrabi, Chung Jung Lee, Wen Yi Hung
The present paper implemented a finite-element methodology to simulate the interaction behavior between tunnel and sandy soil deposit when a reverse fault rupture propagated from the base rock to the ground surface. The location of shear zones and propagation of subsurface rupture traces through overlying sand were discussed with the changes in the tunnel location, tunnel rigidity and soil relative density. The results indicated that the presence of a tunnel could have a significant influence on the fault rupture path. It was further shown that different factors affected the rotation and displacement of the tunnel. This study also investigated the evolution of a surface deformation profile using both centrifuge experiments and the finite element simulation. The results of finite element studies were verified using centrifuge experiments. Reasonable agreement between numerical and experimental results indicated the credibility of the numerical approach. Verified numerical methodology was then used to present a parametric study, offering further insight into the effect of different parameters on the soil-tunnel interaction phenomenon.
PubDate: 2016-01-22T08:06:46Z
- Abstract: Publication date: April 2016
- Constitutive modeling of sand: Formulation of a new plasticity approach
- Abstract: Publication date: March 2016
Source:Soil Dynamics and Earthquake Engineering, Volume 82
Author(s): Panagiota Tasiopoulou, Nikos Gerolymos
A constitutive model for sand is derived based on a new theoretical framework that combines features of perfect elastoplasticity and smooth hysteresis. It resembles a bounding surface model with vanished elastic region, but with considerable modifications in that the plastic modulus is not explicitly defined, and the mapping rule is Bouc–Wen motivated and works equally well in monotonic as in stress-reversal loading. Among the proposed features, are: (a) critical state compatibility not only for monotonic but also for cyclic loading, and (b) novel plastic flow rule accounting for anisotropic distribution of the dilatancy strain ratio, d, to the normal plastic strain increments. The capability of the model in capturing complex aspects of sand behavior (e.g. cyclic mobility, static liquefaction, densification) is demonstrated through illustrative paradigms with emphasis on the physical meaning of each key-model parameter and comparisons with experimental data.
PubDate: 2016-01-18T03:21:24Z
- Abstract: Publication date: March 2016
- Pile response to liquefaction-induced lateral spreading: a shake-table
investigation- Abstract: Publication date: March 2016
Source:Soil Dynamics and Earthquake Engineering, Volume 82
Author(s): Lei Su, Liang Tang, Xianzhang Ling, Chunhui Liu, Xiaoyu Zhang
Case histories have shown that the liquefaction-induced lateral spreading is one of the main causes of damage to pile foundations subjected to seismic loading. This study will investigate the effect of lateral spreading on a single pile behind a quay wall. A shake-table experiment on a single pile embedded in a fully saturated sand stratum is conducted. The ground surface and pile head displacement are in close agreement prior to liquefaction. Upon liquefaction, soil acceleration is clearly attenuated. Simple liquefied lateral soil pressure analysis approaches (uniform and triangular) are calibrated using the experimental results. Subsequently, a Beam on Nonlinear Winkler Foundation (BNWF) model is proposed, and the response is compared to the experimental results. It is found that the proposed BNWF model better predicts the observed pile response compared to the simple soil pressure approaches. A parametric study through the BNWF model is performed to explore the effect of several salient factors on the pile behavior. On this basis, it is shown that a larger pile bending stiffness decreases the lateral spreading-induced deformation, and a larger pile diameter for the same stiffness results in a higher displacement and bending moment.
PubDate: 2016-01-14T03:07:28Z
- Abstract: Publication date: March 2016
- Corrigendum to: “Generalized cyclic p–y curve modeling for
analysis of laterally loaded piles” [Soil Dyn. Earthq. Eng. 63
(2014) 138–149]- Abstract: Publication date: Available online 13 January 2016
Source:Soil Dynamics and Earthquake Engineering
Author(s): Mehdi Heidari, Hesham El Naggar, Mojtaba Jahanandish, Arsalan Ghahraman
PubDate: 2016-01-14T03:07:28Z
- Abstract: Publication date: Available online 13 January 2016
- Dam–reservoir interaction effects on the elastic dynamic response of
concrete and earth dams- Abstract: Publication date: March 2016
Source:Soil Dynamics and Earthquake Engineering, Volume 82
Author(s): Loizos Pelecanos, Stavroula Kontoe, Lidija Zdravković
The relative effects of dam–reservoir interaction on the dynamic response of concrete and earth dams are studied. The amplification of accelerations at the dam crest is explored under harmonic acceleration load. For certain cases of concrete dams the accelerations can be significantly affected by the upstream reservoir, whereas this influence is smaller for earth dams.
PubDate: 2016-01-10T11:15:05Z
- Abstract: Publication date: March 2016
- An innovative cyclic loading device to study long term performance of
offshore wind turbines- Abstract: Publication date: March 2016
Source:Soil Dynamics and Earthquake Engineering, Volume 82
Author(s): G. Nikitas, Nathan J. Vimalan, S. Bhattacharya
One of the major uncertainties in the design of offshore wind turbines is the prediction of long term performance of the foundation i.e. the effect of millions of cycles of cyclic and dynamic loads on the foundation. This technical note presents a simple and easily scalable loading device that is able to apply millions of cycles of cyclic as well as dynamic loading to a scaled model to evaluate the long term performance. Furthermore, the device is economic and is able to replicate complex waveforms (in terms of frequency and amplitude) and also study the wind and wave misalignment aspects. The proposed test methodology may also suffice the requirements of Technology Readiness Level (TRL) Level 3–4 i.e. Experimental Proof of Concept validation as described by European Commission. Typical long term test results from two types of foundations (monopile and twisted jacket on piles) are presented to show the effectiveness of the loading device.
PubDate: 2016-01-10T11:15:05Z
- Abstract: Publication date: March 2016
- A stochastic ground motion accelerogram model for Northwest Europe
- Abstract: Publication date: March 2016
Source:Soil Dynamics and Earthquake Engineering, Volume 82
Author(s): Carlos Medel-Vera, Tianjian Ji
This article presents a stochastic ground-motion accelerogram model for Northwest Europe which simulates accelerograms compatible with seismic scenarios defined by earthquake magnitudes 4<Mw <6.5, distance-to-site 10km<Repi <100km and different types of soil (rock, stiff and soft soil). This model is developed based on Rezaeian and Der Kiureghian (2008, 2010) [1,2] and is a set of predictive equations that define a time-modulated filtered white-noise process. Such predictive equations were calibrated by means of the random-effects regression technique using a subset of the European database of accelerograms. The model is validated in terms of PGA, PGV and spectral accelerations using GMPEs for the UK, Europe and Middle East, and other Stable Continental Regions. This model is the first of its kind for NW Europe.
PubDate: 2016-01-10T11:15:05Z
- Abstract: Publication date: March 2016
- Parametric investigation for rigid circular foundations undergoing
vertical and torsional vibrations- Abstract: Publication date: March 2016
Source:Soil Dynamics and Earthquake Engineering, Volume 82
Author(s): Shi-Shuenn Chen, Ke-Hung Liao, Jun-Yang Shi
This study derives the vertical and torsional responses of a rigid circular foundation resting on unbounded soil. The rigid foundation is subjected to vertical incident P-waves, torsional incident waves, vertical harmonic forces, and harmonic torques, respectively. The solutions of the proposed method are found to agree well with existing solutions of previous research. Results of dimensionless parameter analysis show that the vertical response of the rigid surface foundation can be simplified to a function of the Poisson ratio, the dimensionless frequency and mass ratio, and that the torsional response can be further simplified to a function of dimensionless frequency and mass ratio. As the dimensionless mass ratio increases, the vertical and torsional responses increase at low frequencies but decrease at high frequencies, while the fundamental frequency of the foundation-soil system also decreases. As the Poisson ratio increases, the vertical response increases at low frequencies but increases at high frequencies, while the fundamental frequency of the system increases. As the damping ratio of the viscoelastic half-space increases, the vertical and torsional responses rapidly decrease, and the fundamental frequency of the system slightly decreases. The study found significant characteristics of dynamic responses for the foundation undergoing vertical and torsional vibrations, which can provide helpful physical insights for foundation designs.
PubDate: 2016-01-10T11:15:05Z
- Abstract: Publication date: March 2016
- Seismic pressures on rigid cantilever walls retaining elastic continuously
non-homogeneous soil: An exact solution- Abstract: Publication date: March 2016
Source:Soil Dynamics and Earthquake Engineering, Volume 82
Author(s): C. Vrettos, D.E. Beskos, T. Triantafyllidis
The dynamic response of an elastic continuously nonhomogeneous soil layer over bedrock retained by a pair of rigid cantilever walls to a horizontal seismic motion and the associated seismic pressure acting on these walls are determined analytically–numerically. The soil non-homogeneity is described by a shear modulus increasing nonlinearly with depth. The problem is solved in the frequency domain under conditions of plane strain and its exact solution is obtained analytically. This is accomplished with the aid of Fourier series along the horizontal direction and solution of the resulting system of two ordinary differential equations with variable coefficients by the method of Frobenius in power series. Due to the complexity of the various analytical expressions, the final results are determined numerically. These results include seismic pressures, resultant horizontal forces and bending moments acting on the walls. The solution of the problem involving a single retaining wall can be obtained as a special case by assuming the distance between the two walls to be very large. Results are presented in terms of numerical values and graphs using suitable dimensionless quantities. The effect of soil non-homogeneity on the system response is assessed through comparisons for typical sets of the parameters involved.
PubDate: 2016-01-06T14:37:52Z
- Abstract: Publication date: March 2016
- Shaking table test of a multi-story subway station under pulse-like ground
motions- Abstract: Publication date: March 2016
Source:Soil Dynamics and Earthquake Engineering, Volume 82
Author(s): Zhiyi Chen, Wei Chen, Yueyang Li, Yong Yuan
A series of shaking table tests were conducted to investigate the effect of pulse-like ground motion on a multi-story subway station. Dynamic response data, including internal forces, column drift, and settlement and deformation of the soil were obtained and analyzed. Results show that the pulse-like ground motion increases dynamic responses of the subway station and surrounding soils mainly owing to its inherent rich low-frequency component and high energy. In terms of the structure, central columns, especially central columns on a floor with large story height, are vulnerable components of a multi-story subway station. Both the dynamic earth pressure and the deformation mode of the side wall were analyzed.
PubDate: 2015-12-29T06:00:37Z
- Abstract: Publication date: March 2016
- On the selection of ground–motion attenuation relations for seismic
hazard assessment of the Peninsular Malaysia region due to distant
Sumatran subduction intraslab earthquakes- Abstract: Publication date: March 2016
Source:Soil Dynamics and Earthquake Engineering, Volume 82
Author(s): Abdollah Vaez Shoushtari, Azlan Bin Adnan, Mehdi Zare
The assessment of seismic hazard from seismicity especially those induced by either subduction interface or intraslab earthquakes requires appropriate ground-motion attenuation relations that are tuned to a suitable magnitude–distance range. The Peninsular Malaysia region could be subject to a remarkable seismic hazard due to the large-magnitude, long-distance earthquakes from the Sumatran subduction zone. The earthquakes from Sumatran subduction intraslab zone have not been taken into special consideration in terms of applying the applicable ground-motion relations in the most previous probabilistic seismic hazard assessment (PSHA) studies for the region. This study has attempted first to derive response spectral ground-motion attenuation relations for distant subduction intraslab earthquakes based on the ground-motion data recorded in Peninsular Malaysia, Japan, and Iran. The response spectra database has been compiled from hundreds of ground motions from subduction intraslab events of moment magnitude (M) 5.0–7.7 recorded at sites with hypocentral distance (Rhyp ) of about 120 up to 1400km. The proposed empirical relations are for peak ground acceleration (PGA), peak ground velocity (PGV), and 5% damped pseudo-acceleration (PSA) for four site classes (i.e., National Earthquake Hazards Reduction Program (NEHRP) site classes B, C, D, and E). Second, an evaluation of the applicability of the present study, the global and overseas regional ground-motion relations to the Sumatran subduction intraslab earthquakes has been presented in order to develop ground-motion logic tree for seismic hazard assessment in the Peninsular Malaysia region.
PubDate: 2015-12-29T06:00:37Z
- Abstract: Publication date: March 2016
- Evaluating nonlinear effective stress site response analyses using records
from the Canterbury earthquake sequence- Abstract: Publication date: March 2016
Source:Soil Dynamics and Earthquake Engineering, Volume 82
Author(s): Christopher S. Markham, Jonathan D. Bray, Jorge Macedo, Roberto Luque
A widely used one-dimensional nonlinear effective stress site response analysis program is used to model the response of potentially liquefiable soils during strong shaking. Ground motion records from six events of the 2010–2011 Canterbury earthquake sequence and the extensive site investigation data that have been obtained for the Christchurch area provide the basis for the analyses. The results of the analyses depend significantly on the input motions and soil profile characterization, so these important aspects are examined. Deconvolved Riccarton Gravel input motions were generated, because recorded rock or firm layer motions were not available. Nonlinear effective stress seismic site response analyses are shown to capture key aspects of the observed soil response through the comparison of acceleration response spectra of calculated surface motions to those of recorded surface motions; however, equivalent-linear and total stress nonlinear analyses capture these aspects as well. Biases in the computed motions compared to recorded motions were realized for some cases but they can be attributed primarily to the uncertainty in the development of the input motions used in the analyses.
PubDate: 2015-12-29T06:00:37Z
- Abstract: Publication date: March 2016
- Nonlinear site response from the strong ground-motion recordings in
western China- Abstract: Publication date: March 2016
Source:Soil Dynamics and Earthquake Engineering, Volume 82
Author(s): Mianshui Rong, Zhenming Wang, Edward W. Woolery, Yuejun Lyu, Xiaojun Li, Shanyou Li
Strong ground-motion records from the mainshocks and aftershocks of the 2008 Wenchuan (Ms 8.0) and 2013 Lushan (Ms 7.0) earthquakes, within 300km from the faults, were used for horizontal-to-vertical spectral ratio (HVSR) analysis. The HVRSs of the S-wave show that the predominant site frequency decreases with increasing ground-motion level, a characteristic of nonlinear dynamic soil response. We applied diffuse field theory and Monte Carlo search in the model space to produce an inverted shear-wave velocity profile using the HVSRs of weak S-wave motions. The inverted velocity structures are significantly different from the initial ones derived from in-situ measurements. We also applied 1-D equivalent-linear site-response analysis to derive the spectral ratios (i.e., transfer function) for the original and inverted soil models, and compared the results with the observed HVRSs of the S-wave motions. The comparisons showed that the spectral ratios from 1-D simulation for the inverted soil models agree quite well with the observed HVRSs. In other words, this study suggests that the HVSR from observed earthquake ground motion resembles the empirical transfer function of nonlinear site-response.
PubDate: 2015-12-25T05:55:30Z
- Abstract: Publication date: March 2016
- Editorial Board / Aims and Scope
- Abstract: Publication date: February 2016
Source:Soil Dynamics and Earthquake Engineering, Volume 81
PubDate: 2015-12-25T05:55:30Z
- Abstract: Publication date: February 2016
- Sensitivity analysis of the seismic response of gravity quay walls to
perturbations of input parameters- Abstract: Publication date: March 2016
Source:Soil Dynamics and Earthquake Engineering, Volume 82
Author(s): Armando Calabrese, Carlo G. Lai
Gravity quay walls are extremely common geotechnical systems in many ports. In earthquake-prone regions it is important to assess the seismic behavior of such berths, and to determine which input parameters have the largest effect on the response. This study presents a seismic sensitivity analysis of a blockwork wharf, wherein the effects of inherent variations of ground motions and geotechnical quantities are investigated. An advanced finite difference model is used to propagate the uncertainties, and several nonlinear dynamic analyses are performed for this purpose. Two methodologies are also adopted: Tornado and First Order Second Moment (FOSM). Results from both approaches are found to be in fair agreement, and throw light on the relative importance of input parameters for the considered case. It is showed that the uncertainties associated with the seismic input, i.e. intensity level and ground motion definition, are the most relevant ones. Then there are the effects of the geotechnical parameters, the largest of which is given by the friction angle of the backfill.
PubDate: 2015-12-21T05:55:18Z
- Abstract: Publication date: March 2016
- Principle of superposition for assessing horizontal dynamic response of
pile groups encompassing soil nonlinearity- Abstract: Publication date: March 2016
Source:Soil Dynamics and Earthquake Engineering, Volume 82
Author(s): Chandra Shekhar Goit, Masato Saitoh, George Mylonakis
Model tests on fixed-head floating piles embedded in dry cohesionless soil (Gifu sand) are carried out under 1-g conditions on a shaking table, to investigate the effects of local soil nonlinearity on the dynamic response of pile groups. Results obtained from these tests are employed to assess the applicability of Poulos׳ superposition method in determining the pile group response under different levels of material nonlinearity. A wide range of head loading amplitudes inducing low-to-high levels of soil strain are employed for a broad range of frequencies. Utilizing the aforementioned superposition method, horizontal impedance functions of a closely spaced 3×3-pile group are computed based on: (1) experimentally-measured values of horizontal impedance functions for a single pile, and (2) experimentally-measured pile-to-pile interaction factors. Comparisons between computed and measured impedance functions show good agreement for low to intermediate loading amplitudes, suggesting that the superposition method is valid even under moderately nonlinear conditions.
PubDate: 2015-12-21T05:55:18Z
- Abstract: Publication date: March 2016
- Dynamic elastic analysis of 3-D flexible pavements under moving vehicles:
A unified FEM treatment- Abstract: Publication date: March 2016
Source:Soil Dynamics and Earthquake Engineering, Volume 82
Author(s): Niki D. Beskou, Stephanos V. Tsinopoulos, 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. Both the uniform elastic half-space and the layered elastic half-space with or without damping are considered. The moving with constant speed loads (wheels) of the vehicle are simulated by assigning time dependent load values at all the 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. Both concentrated (one or a series of them) and distributed moving loads are considered. Simple supports on rollers and viscous absorbing boundaries of the pavement domain are both considered. Comparisons with analytical exact solutions for the half-space model under moving loads and analytical approximate solutions for the layered half-space model under static loads are made for validation and comparison reasons, respectively. The cases of static versus dynamic loads, of a single load versus a series of loads and low versus high vehicle׳s velocity are also compared and discussed from the viewpoint of how they affect the response of the pavement.
PubDate: 2015-12-21T05:55:18Z
- Abstract: Publication date: March 2016
- Experimental assessment of dynamic lateral resistance of railway concrete
sleeper- Abstract: Publication date: March 2016
Source:Soil Dynamics and Earthquake Engineering, Volume 82
Author(s): M. Esmaeili, S.A.S. Hosseini, M. Sharavi
The single tie (sleeper) push test (STPT) is a common method to evaluate the lateral resistance of a railway track sleeper. This methodology evaluates the lateral resistance phenomenon in a static manner despite the fact that the majority of the exerted loads on a railway track have a dynamic nature. For this reason, a mass–spring–damper numerical model was created to investigate the dynamic lateral interaction between an isolated sleeper and ballast layer in the presence of various lateral impact loads. On the basis of the model outputs, a pendulum loading test device (PLTD) was designed and developed in the laboratory. In this regard, a cylindrical hammer with modifiable mass and triggering angle was installed on a steel frame for imposing lateral impact load on an instrumented concrete sleeper. The graphs of the sleeper–ballast interaction force versus the sleeper lateral displacement were extracted for different masses and triggering angles of the hammer. Considering a same condition for sleeper, the maximum value of this interaction force was called the dynamic lateral resistance (DLR) and static lateral resistance (SLR) respect to the dynamic and static states of lateral loading. Comparing the values of the sleeper DLRs and SLR indicated that unlike the constant SLR of 6.5kN, the DLR was in the range 2–10.2kN in the impact load domain of 3–40kN. However, as a key finding, the average slopes of the DLR and SLR graphs were equivalent in the dynamic and static tests.
PubDate: 2015-12-21T05:55:18Z
- Abstract: Publication date: March 2016
- Dynamic behaviors of underground structures in E-Defense shaking
experiments- Abstract: Publication date: March 2016
Source:Soil Dynamics and Earthquake Engineering, Volume 82
Author(s): Yohsuke Kawamata, Manabu Nakayama, Ikuo Towhata, Susumu Yasuda
In mitigating disasters, underground structures are required to play an important role because they generally perform well even under large seismic loads and can be used as bases for reconstructing damaged cities. Underground structures compose a network, and therefore, disconnections caused by localized damage may induce critical malfunctions. To investigate this problem, a series of shake table tests using large-scale soil-underground structure models was performed at E-Defense, Japan in 2012. The intent of the tests was to capture detailed localized behaviors of underground structures around inground joints and boundaries between two different soil strata. In the experiments, significant failure developed at an inground joint due to displacement of the surrounding soil. In addition, noticeable localized behaviors, such as conversion of horizontal ground displacement to vertical bending of a tunnel appeared around the inground joints. Also, it was found that a flexible segment along underground structures is effective in mitigating damage to those underground structures, but only in its immediate vicinity.
PubDate: 2015-12-21T05:55:18Z
- Abstract: Publication date: March 2016
- Large-scale shaking table model tests on seismically induced failure of
Concrete-Faced Rockfill Dams- Abstract: Publication date: March 2016
Source:Soil Dynamics and Earthquake Engineering, Volume 82
Author(s): Jun Liu, Fuhai Liu, Xianjing Kong, Long Yu
An increasing number of high Concrete-Faced Rockfill Dams (CFRDs) have been and are being built in highly seismic hazardous regions. Because there are few examples, the failure mechanisms for each damaged CFRD still remain unclear, which prevents a rational evaluation of aseismic performance of a CFRD. In this paper, a series of large-scale shaking table tests are conducted to determine the dynamic failure modes of CFRDs, especially the failure mechanism of the face slab. A type of model slab material is developed according to similitude rules. Particle Image Velocimetry (PIV) is used and improved to track the motion of each grain and subsequently measure the entire velocity field of the deforming cross-sections of dam models. The failure processes of the dams, the failure mechanisms of the slab fractures and the slab dislocations are discussed based on the experimental results. The experiments indicate that large deformations of the uppermost part of the dam caused the face slab to curve upward and crack. Another important fracture morphology of the face slab is the dislocation of its joint. The change in the granular fabric caused the granular slope to slide down and thrust outward, eventually dragging the upper half of the face slab down against its lower half; this motion is accompanied by the formation of a joint dislocation. Therefore, the stability and anti-deformation ability of both the downstream slope and the crest region of the upstream slope should be improved to withstand earthquake. The results of the shaking table model tests are consistent with the numerical simulation, and both results support the prototype dam׳s seismically induced failure characteristics.
PubDate: 2015-12-21T05:55:18Z
- Abstract: Publication date: March 2016
- Seismic assessment of the rigid sliding displacements caused by pulse
motions- Abstract: Publication date: March 2016
Source:Soil Dynamics and Earthquake Engineering, Volume 82
Author(s): Jian Song, Guang-Yun Gao, Adrian Rodriguez-Marek, Ellen M. Rathje
This paper presents a comprehensive study on the rigid block sliding displacement of slopes subjected to ground motions with large velocity pulses. A comparison of the performance of various existing empirical displacement models is provided through analyses of the displacement residuals of slopes subject to pulse-like motions. Except for the PGA- and PGV-based Saygili and Rathje model (2008, referred to as SR08), positive medians of residuals are observed for selected models, indicating an under-estimation. There is a negative constant shift in the total residuals for the SR08 model, which can be easily fixed by changing the constant term in the predictive equation. The residuals from the SR08 model also have the smallest standard deviation compared to the other models. A modified SR08 model is developed for predicting rigid block sliding displacements for pulse-like motions. The modified predictive model is used in probabilistic seismic displacement analyses of slopes in a hypothetical near-fault region.
PubDate: 2015-12-13T18:13:18Z
- Abstract: Publication date: March 2016
- Study of the train-induced vibration impact on a historic Bell Tower above
two spatially overlapping metro lines- Abstract: Publication date: February 2016
Source:Soil Dynamics and Earthquake Engineering, Volume 81
Author(s): Meng Ma, Weining Liu, Chunyu Qian, Guohua Deng, Yudong Li
There is concern regarding the long-term vibration effects caused by metro trains on historic buildings. In this paper, the impact of metro train-induced vibrations on the Bell Tower in Xi’an above two spatially overlapping tunnels was studied. Metro Line 2 has been operational since 2011, and Line 6 is still under construction. To study and control the effect of micro vibrations on the Bell Tower, a metro train–track–tunnel–soil 3D dynamic FE model was developed. The vibration response generated by Line 2 was then predicted, and the influences of train speed on ground vibration were analysed. In addition, a detailed in situ measurement, which helped calibrate the numerical model and determine the dynamic behaviour of timber structures, was performed. Finally, the calibrated models and measured results were used to predict vibrations caused by road traffic and trains from two spatially overlapping metro lines. This was performed under different route schemes and train operation conditions. The results showed that installing steel spring floating slab tracks (FST) and decreasing train speeds had obvious effects on controlling the ground peak particle velocity (PPV). Simulated results from both the input impulse and output response generated by metro Line 2 matched well with actual measurements. If correct designs are employed, it is possible to resolve the vibration problem on historic buildings caused by metro trains.
PubDate: 2015-12-08T18:00:36Z
- Abstract: Publication date: February 2016
- Analytical solution of the asymmetric transient wave in a transversely
isotropic half-space due to both buried and surface impulses- Abstract: Publication date: February 2016
Source:Soil Dynamics and Earthquake Engineering, Volume 81
Author(s): Mehdi Raoofian Naeeni, Morteza Eskandari-Ghadi
With the aid of a complete set of two scalar potential functions, the problem of transient wave propagation in transversely isotropic half-space, subjected to time dependent tractions applied on a finite patch at an arbitrary depth below the free surface of the half-space is investigated. With the use of the displacement–potential function relationships in a cylindrical coordinate system, the coupled equations of motion are uncoupled; resulting in two separate partial differential equations one of which is second order and the other is fourth order. These two partial differential equations are solved with the aid of both Fourier series expansion and joint Hankel–Laplace integral transforms. The solutions are also investigated in details for tractions varying with time as Heaviside step function, which may be used as a kernel in any integral based method for more complicated elastodynamic initial-boundary value problems. Moreover, some displacement Green׳s functions are numerically evaluated for a synthetic transversely isotropic material to graphically demonstrate the transient motion of the free surface of the half-space.
PubDate: 2015-12-08T18:00:36Z
- Abstract: Publication date: February 2016
- A comparison of initial stiffness formulations for small-strain
soil–pile dynamic Winkler modelling- Abstract: Publication date: February 2016
Source:Soil Dynamics and Earthquake Engineering, Volume 81
Author(s): L.J. Prendergast, K. Gavin
Dynamic Soil-Structure Interaction (DSSI) is an area of much ongoing research and has wide and varied applications from seismic response analysis to offshore wind foundation response. DSSI covers a wide range of load regimes from small-strain vibrations to large-strain cyclic loading. One of the most common ways to model DSSI uses the Winkler model, which considers the soil as a series of mutually independent springs. The difficulty with modelling DSSI arises with the inelastic and nonlinear load–displacement response of soil with increasing strain, therefore modelling of large-strain DSSI relies on the specification of many interrelated parameters. The relative magnitude of these parameters can have a significant effect on the modelled response. In this paper, the specification of an initial stiffness coefficient to model the elastic (small-strain) response of a soil–pile system is investigated. The coefficient of subgrade reaction method can be used to generate spring stiffness moduli for Winkler type models. A number of subgrade reaction theories have been proposed and their application to the problem of static loading has been widely studied. However, relatively little research concerning the application of these models for small-strain dynamic loading has been undertaken. This paper describes a sensitivity study in which a number of subgrade reaction models were used to estimate the frequency response at small-strain levels for a range of pile geometries and ground conditions. A field investigation was undertaken on two piles with different slenderness ratios to estimate the frequency response and damping ratios. The experimental results were compared to predictions of damped natural frequency obtained from numerical models using the force input and measured damping ratio from each experiment. The ability of each subgrade reaction formulation to model the response at small-strain levels is evaluated.
PubDate: 2015-12-08T18:00:36Z
- Abstract: Publication date: February 2016
- A simplified Nonlinear Sway-Rocking model for evaluation of seismic
response of structures on shallow foundations- Abstract: Publication date: February 2016
Source:Soil Dynamics and Earthquake Engineering, Volume 81
Author(s): Yang Lu, Alec M. Marshall, Iman Hajirasouliha
This paper presents a simplified Nonlinear Sway-Rocking model as a preliminary design tool for seismic soil-structure interaction analysis. The proposed model is intended to capture the nonlinear load-displacement response of shallow foundations during strong earthquake events where foundation bearing capacity is fully mobilised. Emphasis is given to heavily-loaded structures resting on a saturated clay half-space. The variation of soil stiffness and strength with depth, referred to as soil non-homogeneity, is considered in the model. Although independent springs are utilised for each of the swaying and rocking motions, coupling between these motions is taken into account by expressing the load-displacement relations as functions of the factor of safety against vertical bearing capacity failure (FSv) and the moment-to-shear ratio (M/H). The simplified model has been calibrated and validated against results from a series of static push-over and dynamic analyses performed using a more rigorous finite-difference numerical model. Despite some limitations of the current implementation, the concept of this model gives engineers more degrees of freedom in defining their own model components, providing a good balance between simplicity, flexibility and accuracy.
PubDate: 2015-12-08T18:00:36Z
- Abstract: Publication date: February 2016
- Analysis of wave propagation and soil–structure interaction using a
perfectly matched layer model- Abstract: Publication date: February 2016
Source:Soil Dynamics and Earthquake Engineering, Volume 81
Author(s): Josif Josifovski
This paper presents an application of a perfectly matched layer as an absorbing condition for solution of linear wave equations for unbounded domains. The perfectly matched layer can be combined with different numerical methods. In this particular case, a frequency dependent finite element formulation has been pursued. What is most significant is that it utilizes a newly established requirement for definition of the perfectly matched layer, which improves the accuracy and efficiency of the method. In this study, different definitions of the attenuation were considered to optimize the performance of the radiation condition. They were verified in comparison with an exact solution of wave propagation in a half-plane. This analysis was used later to establish a requirement for definition of minimum layer depth as an accuracy prerequisite. Similar requirements are presented for the other nonphysical attenuation parameters. The advantages of the proposed model for a rigid foundation over a half-plane are shown in comparison to other solutions from the literature, but also to exact analytical result. The importance of well-defined boundary condition is best demonstrated when compared to a model with viscous damper boundary. In fact, even if a perfectly matched layer is a rigorous boundary condition, it performs much better, reducing the computational time in half by using fewer elements. Moreover, an application of the approach is presented where the kinematic effects of vibrating foundation for different ground conditions are evaluated.
PubDate: 2015-12-08T18:00:36Z
- Abstract: Publication date: February 2016
- In-plane soil–structure interaction in layered, fluid-saturated,
poroelastic half-space I: Structural response- Abstract: Publication date: February 2016
Source:Soil Dynamics and Earthquake Engineering, Volume 81
Author(s): Jianwen Liang, Jia Fu, Maria I. Todorovska, Mihailo D. Trifunac
Linear in-plane soil–structure interaction in two dimensions (2D) is studied in fluid-saturated, poroelastic, layered half-space using the Indirect Boundary Element Method (IBEM). The structure is a shear wall supported by a rigid embedded foundation. Exact stiffness matrices for the soil layer and half-space, and Green׳s functions of uniformly distributed loads and pore pressure on an inclined line are derived. Results of the system response in the frequency domain are presented for the special case of single soil layer over bedrock, semi-circular foundation and zero seepage force. The effects of water saturation, soil porosity, depth of soil layer, rigidity contrast between layer and bedrock are investigated in the frequency domain for incident plane P- and SV waves. The results suggest that water saturation may cause increase of the system frequency by more than 10%.
PubDate: 2015-12-08T18:00:36Z
- Abstract: Publication date: February 2016
- Comparison of different models for friction pendulum isolators in
structures subjected to horizontal and vertical ground motions- Abstract: Publication date: February 2016
Source:Soil Dynamics and Earthquake Engineering, Volume 81
Author(s): Luca Landi, Gianluca Grazi, Pier Paolo Diotallevi
This research focuses on the different modelling approaches for the simulation of the seismic response of structures with friction pendulum isolation systems. The behaviour of such systems is strongly affected by several parameters, as for example the friction coefficient and the axial load. The latter has a particular importance in presence of seismic actions characterized by the simultaneous presence of high horizontal and vertical accelerations. To study these aspects, several nonlinear dynamic analyses have been performed considering a two degree of freedom model isolated at the base and subjected to recorded horizontal and vertical ground motions. The response of the selected isolation systems has been studied through different models, starting by the more simple ones based on a constant friction coefficient to the more complex ones based on a friction coefficient varying with the sliding velocity and axial force. A set of ground motions with near field records characterized by different values of the ratio between peak vertical and horizontal accelerations has been considered. The results have allowed to compare the different models and to study the effect of the vertical seismic component on the response of the isolators.
PubDate: 2015-12-08T18:00:36Z
- Abstract: Publication date: February 2016
- Editorial Board / Aims and Scope
- Abstract: Publication date: January 2016
Source:Soil Dynamics and Earthquake Engineering, Volume 80
PubDate: 2015-12-03T17:50:50Z
- Abstract: Publication date: January 2016
- Vertical dynamic impedance of the support plate of the Rod-less drilling
rig in layered soil- Abstract: Publication date: January 2016
Source:Soil Dynamics and Earthquake Engineering, Volume 80
Author(s): Wen-Wu Liu, Chang-Sheng Hu, Nian-Li Lu
The vertical dynamic response of the support plate of the Rod-less drilling rig in layered soil is theoretically investigated. The soil layers are modeled as a set of viscoelastic continuous media, and the distributed Voigt model is proposed to simulate the dynamic interactions of the adjacent soil layers. Meanwhile, the support plate is regarded as an annular friction pile with a certain radian and can be divided into several plate segments allowing for soil layers. The governing equation of soil vibration is solved by virtue of the Laplace transform and the separation of variables method. Then the vertical dynamic impedance at the bottom of the support plate is derived by means of the impedance function transfer method as well as the force and displacement continuity conditions at the soil–plate interface. By means of the inverse Fourier transform and convolution theorem, the velocity response in the time domain can also be obtained. The reasonableness of the assumptions of the support plate and soil–layer interactions has been verified by comparing the present solutions with dynamic experiments on a full-scale plate in the field. It is shown that the solution derived in this study agrees better with the experimental one than the more limited solution of Novak. An extensive parametric study has been conducted to investigate the effects of major parameters.
PubDate: 2015-11-12T07:46:07Z
- Abstract: Publication date: January 2016
- Dynamic responses of structure–soil–structure systems with an
extension of the equivalent linear soil modeling- Abstract: Publication date: January 2016
Source:Soil Dynamics and Earthquake Engineering, Volume 80
Author(s): M. Ghandil, F. Behnamfar, M. Vafaeian
A three-dimensional problem of cross interaction of adjacent structures through the underlying soil under seismic ground motion is investigated. The story shears and lateral relative displacements (drifts) are the targets of the computations. These are calculated using a detailed modeling of soil, the foundations and the two adjacent structures. An equivalent linear behavior is assumed for the soil by introducing reduced mechanical properties consistent with the level of ground shaking for the free-field soil. Then a distinctive soil zone (the near-field soil) is recognized in the vicinity of the foundations where the peak shear strain under the combined effect of a severe earthquake and the presence of structures is much larger than the strain threshold up to which the soil can be modeled as an equivalent linear medium. It is shown that it is still possible to use an equivalent linear behavior for the near-field soil if its shear modulus is further reduced with a factor depending on the dynamic properties of the adjacent structures, the near-field soil, and the design earthquake. Variations of the dynamic responses of different adjacent structures with their clear distances are also discussed.
PubDate: 2015-11-12T07:46:07Z
- Abstract: Publication date: January 2016
- A borehole seismic source and its application to measure in-situ seismic
wave velocities of geo-materials- Abstract: Publication date: January 2016
Source:Soil Dynamics and Earthquake Engineering, Volume 80
Author(s): Young Jin Mok, Chul Soo Park, Boo Hyun Nam
A borehole seismic source was developed to measure horizontally-polarized shear (SH-) waves in the near surface and to improve drawbacks of conventional seismic sources. An electro-mechanical-type source, called “TahcBalm”, has exceptional repeatability in generating signature SH-waves, while being sufficiently small and light to be fitted in 76mm diameter cased or uncased boreholes. The source has been extensively used for borehole seismic testing at various locations with diverse soil and rock conditions. The cross-hole and in-hole testing signals are strong enough and allow the clear identification of the first arrival of SH-waves in all tested geologic environments. TahcBalm generates SH-waves with proper wavelength of about 1m and 0.5m for cross-hole and in-hole testing configurations respectively, at soil and rock sites. The source performs well in terms of data quality and ease of use.
PubDate: 2015-11-08T07:37:34Z
- Abstract: Publication date: January 2016
- A predictive model for fling-step in near-fault ground motions based on
recordings and simulations- Abstract: Publication date: January 2016
Source:Soil Dynamics and Earthquake Engineering, Volume 80
Author(s): Lynne S. Burks, Jack W. Baker
We identify potential data sources for fling-step and discuss their value, compile a dataset of simulated and recorded ground motions containing fling, extract fling pulses from these ground motions, and derive a predictive model for fling amplitude and period that is compared to existing empirical models. Fling is the result of permanent static offset of the ground during an earthquake, but is usually ignored because ground motion records from accelerometers contain errors that make it difficult to measure static offsets. However, some data sources include fling, such as specially processed recordings, ground motion simulations, and high-rate global positioning systems (GPS). From this data, we extract fling pulses using the pattern search global optimization algorithm. The resulting displacement amplitudes and periods are used to create a new predictive equation for fling parameters, are compared to existing empirical models for pulse period, fling amplitude, and surface displacement along the fault, and are found to match reasonably well.
PubDate: 2015-11-08T07:37:34Z
- Abstract: Publication date: January 2016
- Effects of soil–structure interaction on distribution of seismic
vulnerability in RC structures- Abstract: Publication date: January 2016
Source:Soil Dynamics and Earthquake Engineering, Volume 80
Author(s): F. Behnamfar, M. Banizadeh
Seismic vulnerability analysis of structures is usually accomplished without regard for soil–structure interaction (SSI). This is while accounting for SSI can result in variation of intensity and distribution of seismic vulnerabilities especially when a more rigorous analysis is implemented by nonlinear modeling of both structure and its underlying soil. This study moves in the same direction. Reinforced concrete buildings being 3, 5, 6, 8, 9 stories high, resting on soft and very soft soil types, once with moment resisting and once with concrete shear walls are considered. Twenty suits of 10 ground motions (200 records) consistent with 5 buildings with two different lateral load bearing systems on two types of soils are selected and scaled for nonlinear dynamic analysis of buildings. The analysis is once implemented for fixed-based and once for flexible-base buildings. The results show that contrary to the common belief, with a flexible-base, the location of maximum drift shifts to the first story where the most intensive vulnerability is observed. SSI changes the pattern of distribution of vulnerability especially for the beams of shear wall buildings and intensifies the seismic vulnerability on soft soils.
PubDate: 2015-11-03T20:50:04Z
- Abstract: Publication date: January 2016
- Effects of tectonic regime and soil conditions on the pulse period of
near-fault ground motions- Abstract: Publication date: January 2016
Source:Soil Dynamics and Earthquake Engineering, Volume 80
Author(s): Timothy G. Cork, Jung Han Kim, George P. Mavroeidis, Jae Kwan Kim, Benedikt Halldorsson, Apostolos S. Papageorgiou
In this article, the effects of site conditions (rock vs. soil) and tectonic regime (interplate vs. intraplate) on the pulse period of near-fault forward-directivity ground motions are investigated through linear regression analyses, and appropriate scaling laws that relate the pulse period to the earthquake magnitude are derived. The analyses of rock and soil sites are performed using interplate records only. The results show that for earthquakes of smaller magnitude, the pulse period is longer at soil sites than at rock sites. As the earthquake magnitude increases, the pulse period values at rock and soil sites converge. This observation is in agreement with findings reported in previous studies. However, as shown in this article, the effect of soil conditions on the pulse period is not statistically significant at the 10% level based on the available near-fault ground motion datasets. Regression analyses for interplate and intraplate records are also performed, including regressions with and without self-similarity. The results show that the pulse periods of interplate records are significantly longer (factor of 2.45, on average) than the pulse periods of intraplate records with similar magnitude. It is demonstrated that this difference should also be reflected in the rise times of the events originating in the two different tectonic regimes. Using the specific barrier model as a “tool” of analysis, it is shown that the significant difference in the pulse periods also implies a significant difference (factor of 4) in the local stress drops for the events of the two tectonic regimes. This latter conclusion is supported by recent reports in the literature of the reanalysis of eastern North American earthquakes, accounting more carefully for attenuation.
PubDate: 2015-11-03T20:50:04Z
- Abstract: Publication date: January 2016
- Design of a variable stiffness bracing system: Mathematical modeling,
fabrication, and dynamic analysis- Abstract: Publication date: January 2016
Source:Soil Dynamics and Earthquake Engineering, Volume 80
Author(s): Amir Fateh, Farzad Hejazi, Mohd Saleh Jaafar, Izian Abd. Karim, Azlan Bin Adnan
This paper presents a new bracing system with variable stiffness springs; this adaptive structural control system is designed to protect buildings against severe vibration and ground movement. The developed variable stiffness bracing (VSB) system comprises four nonlinear steel leaf springs that provide nonlinear and variable stiffness capacity at different frame displacements. The inelastic actions of the VSB system׳s nonlinear leaf springs keep the energy dissipation characteristics and ductility of moment-resisting frames. At large vibration amplitudes, the VSB device restrains unallowably story drift. Therefore, frames display ductile performance. We developed a mathematical model to simulate the mechanical behavior of the system, including the stiffness nonlinearity of the springs. Moreover, we evaluated the efficiency of the VSB implementation in a single-degree-of-freedom system by dynamically analyzing different models: a moment-resisting frame, a conventional braced frame, and a frame using the VSB system. This article discusses and proves the effectiveness of the proposed system through numerical analysis.
PubDate: 2015-11-03T20:50:04Z
- Abstract: Publication date: January 2016
- Use of offshore wind farms to increase seismic resilience of Nuclear Power
Plants- Abstract: Publication date: January 2016
Source:Soil Dynamics and Earthquake Engineering, Volume 80
Author(s): S. Bhattacharya, K. Goda
One of the challenges faced by the engineering profession is to meet the energy requirement of an increasingly prosperous world. Nuclear power was considered as a reliable option until the Fukushima Daiichi Nuclear Power Plant (NPP) disaster which eroded the public confidence. This short paper shows that offshore wind turbines (due to its shape and form, i.e. heavy rotating mass resting at the top of a tall tower) have long natural vibration periods (>3.0s) and are less susceptible to earthquake dynamics. The performance of near-shore wind turbines structures during the 2011 Tohoku earthquake is reviewed. It has been observed that they performed well. As NPPs are often sited close to the sea, it is proposed that a small wind farm capable of supplying emergency backup power along with a NPP can be a better safety system (robust and resilient system) in avoiding cascading failures and catastrophic consequences.
PubDate: 2015-10-27T19:47:04Z
- Abstract: Publication date: January 2016
- Propagation of torsional surface waves in a double porous layer lying over
a Gibson half space- Abstract: Publication date: January 2016
Source:Soil Dynamics and Earthquake Engineering, Volume 80
Author(s): Sushant Shekhar, Imtiyaz A. Parvez
The present study deals with the behavior of torsional surface waves when they propagate through an inhomogeneous fluid saturated porous double layers over a dry sandy inhomogeneous Gibson half space. The inhomogeneities of the porous layers are taken as quadratic and exponential variation with depth in the density, elastic moduli and initial stress. In the half space it varies linearly in the elastic moduli and initial stress. For simplicity of the problem, we have used the separation of variable technique. The dispersion equation has been derived with boundary conditions and solved by an iterative method (Newton Raphson method). We have also converted our dynamical equations into non-dimensional form. It has been observed from the numerical validation of the proposed model that the presence of the initial stress and inhomogeneity of both media affect significantly the phase velocity of torsional surface waves. The effect of initial stress, inhomogeneity parameters, depth ratio, sandy parameter, Biot׳s gravity parameter and porosity of the layer on the dimensionless phase velocity of the torsional surface waves are demonstrated graphically with respect to the non-dimensional wave number kH 1 (where k is the wave number and H 1 is the thickness of the second porous layer).
PubDate: 2015-10-27T19:47:04Z
- Abstract: Publication date: January 2016
- Vulnerability of floating tunnel shafts for increasing earthquake loading
- Abstract: Publication date: January 2016
Source:Soil Dynamics and Earthquake Engineering, Volume 80
Author(s): Juan M. Mayoral, Sotiris Argyroudis, Ernesto Castañon
Fragility curves constitute the cornerstone in seismic risk evaluations and performance-based earthquake engineering. They describe the probability of a structure to experience a certain damage level for a given earthquake intensity measure, providing a relationship between seismic hazard and vulnerability. In this paper a numerical approach is applied to derive fragility curves for tunnel shafts built in clays, a component that is found in several critical infrastructure such as urban metro networks, airport facilities or water and waste water projects. The seismic response of a representative tunnel shaft is assessed using tridimensional finite difference non-linear analyses carried out with the program FLAC3D, under increasing levels of seismic intensity. A hysteretic model is used to simulate the soil non-linear behavior during the seismic event. The effect of soil conditions and ground motion characteristics on the soil-structure system response is accounted for in the analyses. The damage is defined based on the exceedance of the concrete wall shaft capacity due to the developed seismic forces. The fragility curves are estimated in terms of peak ground acceleration at a rock or stiff soil outcrop, based on the evolution of damage with increasing earthquake intensity. The proposed fragility models allows the characterization of the seismic risk of a representative tunnel shaft typology and soil conditions considering the associated uncertainties, and partially fill the gap of data required in performing a risk analysis assessment of tunnels shafts.
Graphical abstract
PubDate: 2015-10-27T19:47:04Z
- Abstract: Publication date: January 2016
- Effects of cross-anisotropic soil behaviour on the wave-induced residual
liquefaction in the vicinity of pipeline buried in elasto-plastic seabed
foundations- Abstract: Publication date: January 2016
Source:Soil Dynamics and Earthquake Engineering, Volume 80
Author(s): H.-Y. Zhao, D.-S. Jeng, C.C. Liao
In this paper, a two-dimensional integrated numerical model is developed to examine the influences of cross-anisotropic soil behaviour on the wave-induced residual liquefaction in the vicinity of a pipeline buried in a porous seabed. In the wave model, the RANS (Reynolds Averaged Navier–Stokes) equation is used to govern the wave motion. In the seabed model, the residual soil response in the vicinity of an embedded pipeline is considered with the 2-D elasto-plastic solution, where the phase-resolved shear stress is used as a source for the build-up of residual pore pressure. Classical Biot׳s consolidation equation is used for linking the solid-pore fluid interaction. The validation of the proposed integrated numerical model is conducted by the comparisons with the previous experimental data. Numerical examples show that the pore pressures can accumulate to a large value, thus resulting in a larger area of liquefaction potential in the given anisotropic soil compared to that with isotropic solution. The influences of anisotropic parameters on the wave-induced residual soil response in the vicinity of pipeline are significant. A high rate of pore pressure accumulation and dissipation is observed and the liquefaction potential develops faster as the anisotropic parameters increase. Finally, a simplified approximation based on a detailed parametric investigations is proposed for the evaluation of maximum liquefaction depth (z L ) in engineering application.
PubDate: 2015-10-27T19:47:04Z
- Abstract: Publication date: January 2016
- A generalized multi-level seismic damage model for RC framed structures
- Abstract: Publication date: January 2016
Source:Soil Dynamics and Earthquake Engineering, Volume 80
Author(s): Jianguang Yue, Jiang Qian, Dimitri E. Beskos
A generalized multi-level damage model is developed to evaluate the seismic damage of reinforced concrete (RC) framed structures. This model is a deformation-based continuum damage model with stiffness degradation and is based on a deformation equivalent principle and generalized force–deformation relationships for concrete and its steel reinforcement. The model is called multi-level in the sense that is associated with many performance levels (e.g., immediate occupancy, life safety, collapse prevention) and structural levels (e.g., material, member, structure). Thus, it has different damage indicators for the various structural levels with specific limit values at each performance level. In order to build the correlations between the generalized damage model and the multi-level damage performance, a normalized corresponding parameter is introduced into the damage model to specify the damage limit values at each structural level. The normalized corresponding parameters are obtained by statistical analysis of results coming from finite element response calculations and tests involving 400 RC columns and 54 loading-cases of a 12-storey model frame structure. The proposed damage model is used to study evolution at various structural levels for a 12-storey model frame structure and a real tested in situ structure consisting of RC frame skeleton and masonry walls. The finite element method utilizing the proposed damage model produces results in good agreement with those of the tests.
PubDate: 2015-10-27T19:47:04Z
- Abstract: Publication date: January 2016
- Multi-transmitting formula for finite element modeling of wave propagation
in a saturated poroelastic medium- Abstract: Publication date: January 2016
Source:Soil Dynamics and Earthquake Engineering, Volume 80
Author(s): Li Shi, Peng Wang, Yuanqiang Cai, Zhigang Cao
An absorbing boundary condition that is called the multi-transmitting formula (MTF) was originally proposed by Liao and Wong for wave propagation in an elastic medium. In this paper, the MTF was extended for modeling wave propagation in a saturated poroelastic medium using the finite element method. Reflection coefficients of the MTF that is applied to the boundaries of a finite element grid were analytically derived for the incidence of SV, P1 and P2 waves, respectively. The effects of the excitation frequency and the artificial wave velocity on the reflection coefficients of the MTF were theoretically investigated. The MTF was then implemented into a finite element code to examine its capacity to absorb the one-dimensional longitudinal/shear wave, the plain-strain waves, the moving-load generated waves and the three-dimensional waves in the saturated poroelastic medium. It is found that the reflection coefficients evaluated from the numerical simulation agree with the predicted values in the theoretical investigations.
PubDate: 2015-10-27T19:47:04Z
- Abstract: Publication date: January 2016