Centrifuge Modeling Studies of Site Response in Soft Clay over Wide Strain Range

Afacan, Kamil Bekir; Brandenberg, Scott J.; Stewart, Jonathan P.

doi:10.1061/(asce)gt.1943-5606.0001014

Cited by 58 publications

(30 citation statements)

References 24 publications

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“…Recent work from Afacan et al [1] on centrifuge modeling of site response in soft clays over a wide range of strains that included nearly linear to strongly nonlinear soil behavior concluded that centrifuge tests using a hinged-plate container are valuable to understand 1-D seismic ground response and to validate nonlinear site response from empirical and numerical models. They did not present a comparison with numerical simulations in the paper, but according to the results presented, the Darendeli [5] functional form appeared to provide a reasonable characterization of the observed modulus-reduction behavior in the centrifuge models.…”

Section: Introductionmentioning

confidence: 98%

Evaluation of 1-D seismic site response modeling of sand using centrifuge experiments

Hashash

Dashti

Romero

et al. 2015

Soil Dynamics and Earthquake Engineering

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a b s t r a c tThe response of an equivalent 26 m-thick deposit of dry, medium-dense, Nevada Sand with a relative density of 60% is measured in the centrifuge under six 1-D, horizontal earthquake motions applied to the base of the centrifuge container. Several 1-D site response analysis techniques are employed to simulate the experiments, including (a) equivalent linear analyses, (b) nonlinear analyses using a multi-degree-offreedom, lumped mass model, and (c) finite element analyses of a soil column using a pressuredependent, multi-yield, plasticity soil model. An average V s profile was estimated using empirical correlations. Soil dynamic properties included published generic modulus reduction and damping curves with implied strength correction as well as recommended plasticity model parameters based on soil index properties. Computed and measured lateral displacements, accelerations, shear strains, spectral accelerations, and Arias Intensities are presented and their differences are quantified in terms of mean residuals and variance. The comparisons demonstrate that 1-D seismic site response analyses using the available strength corrected, generic, pressure-dependent modulus reduction and damping curves for medium-dense dry sand can reliably compute soil response under 1-D wave propagation using any of the three methods, with an absolute mean residual of less than 0.5.

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Section: Introductionmentioning

confidence: 98%

Evaluation of 1-D seismic site response modeling of sand using centrifuge experiments

Hashash

Dashti

Romero

et al. 2015

Soil Dynamics and Earthquake Engineering

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“…In this case, the surrounding soil may undergo large shear strains during earthquake shaking beyond the linear range which makes the accuracy of linear or equivalent linear models at least questionable. In support to the above, recent findings from centrifuge tests on the seismic behavior of soft clays under large intensity levels of input motions ( [15], [16], [17]) revealed attenuation of base acceleration as it propagates through the soil due to the inability of the soft clay to transmit shear stresses close to its limited shear strength. Stiffness degradation with the number of loading cycles has also been observed having a direct impact on the free-field loading imposed on piles [17].…”

Section: Introductionmentioning

confidence: 60%

A Numerical Study on the Filtering Action of Piles in the Soft Clay of Maliakos Gulf, Central Greece

Rovithis¹,

Laora²,

Iovino³

et al. 2019

Proceedings of the 7th International Conference on Computational Methods in Structural Dynamics and Earthquake Engineering (COM

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The potential of piles to reduce the seismic motion transmitted to the superstructure with respect to the free field motion, due to the kinematic interplay between soil and pile, is explored by considering a single pile embedded in the soft marine clay of Maliakos Gulf subsoil in central Greece. The soil profile consists of a very soft normally consolidated clay layer with nearly-zero stiffness at ground surface, increasing proportionally with depth, underlain by a stiffer layer of sandy clay. The problem is tackled numerically by means of Equivalent linear (EL) and strength-controlled non-linear (NL) constitutive laws to model the behavior of the soil under seismic excitation. The latter is chosen on a magnitude-epicentral distance (M-R) basis from the European Strong-motion Database (ESD), taking into account the seismotectonic regime of the broader area under study. Seven (7) motions recorded at soil type A, according to EC8, were chosen to define an average code-compatible spectrum. The average mobilized stiffness of the free field soil obtained from EL and NL analyses is then introduced into a finite-element model of the soil-pile system to investigate the kinematicinduced filtering action of the pile as affected by pile cap embedment depth and pile diameter. The above is quantified in terms of ratios of spectral accelerations at the pile head and free field at ground surface. Results highlight the importance of considering NL response for such type of soils and conclude on the beneficial role of piles as reflected in a large reduction of the free field spectral acceleration, even for piles with relatively small diameter.

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“…Small misfits in the modulus reduction curve can translate to significant misfits in the stressstrain curve at high strain, resulting in errors in the desired shear strength (e.g. [4], [5], [6], [13]).…”

Section: Modulus Reduction Behavior Of Existing Modelsmentioning

confidence: 99%

“…This extrapolation can cause an under-or over-prediction of shear strength depending on the ratio of shear strength to small strain shear modulus, Gmax. These shear strength errors can translate to ground motion prediction errors [4,5,6]. Developing models that accurately capture small strain behavior and shear strength is obviously important for nonlinear site response simulations.…”

Section: Introductionmentioning

confidence: 99%

ARCS: A one dimensional nonlinear soil model for ground response analysis

Yniesta

Brandenberg

Shafiee

2017

Soil Dynamics and Earthquake Engineering

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This paper presents a one dimensional nonlinear stress-strain model called ARCS (Axis Rotation and Cubic Spline) capable of reproducing any user-input modulus reduction and damping curve. Unlike many previous nonlinear models, the ARCS model does not utilize Masing's rules, nor does it require a specific functional form for the backbone curve such as a hyperbola. Rather, the model matches the desired modulus reduction curve by fitting cubic splines to the implied stress-strain curve, and matches the damping curve by utilizing a coordinate transformation technique in which one axis lies along the secant shear modulus line with the other axis in the orthogonal direction for a particular unload-reload cycle. Damping is easily controlled in the transformed coordinate space. An inverse coordinate transformation returns the desired stress. The integration algorithm is independent of strain step size, meaning that the returned stress for a large strain increment is identical to the stress that would be returned by subdividing the strain increment into smaller increments. Small-strain damping may be modeled hysteretically, avoiding the need for supplemental viscous damping. The model is shown to match the results of laboratory cyclic simple shear tests involving deliberately irregular stain histories. The performance of the model is illustrated in a set of ground response simulations where its predictions are compared with those of existing models. The ARCS model does not explicitly account for rate effects, cyclic degradation, or pore pressure generation.However, the equations can potentially be adapted in more advanced constitutive models to capture these effects. Such implementations are reserved for future publications.

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Centrifuge Modeling Studies of Site Response in Soft Clay over Wide Strain Range

Cited by 58 publications

References 24 publications

Evaluation of 1-D seismic site response modeling of sand using centrifuge experiments

Evaluation of 1-D seismic site response modeling of sand using centrifuge experiments

A Numerical Study on the Filtering Action of Piles in the Soft Clay of Maliakos Gulf, Central Greece

ARCS: A one dimensional nonlinear soil model for ground response analysis

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