Equivalent-Linear Dynamic Stiffness of Surface Footings on Liquefiable Soil

Karatzia, Xenia; Mylonakis, George; Bouckovalas, George D.

doi:10.7712/120117.5500.18213

Cited by 4 publications

(7 citation statements)

References 20 publications

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“…Table 7 shows that the maximum PPR 0 is 1.38 in natural foundation case. According to the Eq (22) and (28), the Poisson's ratio is 0.27 which is basically consistent with the Poisson's ratio of sand in Table 1. In others cases, the maximum PPR 0 is different from the natural case due to the interaction between piles and soil.…”

Section: Effect Of Pile Spacing On Pore Water Pressure At Different Dsupporting

confidence: 81%

“…Li et al [21] used the parameter identification method to analyze the test records of soil acceleration and pore water pressure from the shaking table tests for dynamic liquefiable soil-pilestructure interaction system. Karatzia et al [22] studied the influence of liquefaction on the dynamic impedance (stiffness and damping) of rigid square footings resting on liquefiable soil under external harmonic loading. Their results demonstrate that liquefaction in the foundation soil yields the significant degradation of the dynamic spring coefficients and increases the associated damping coefficients under seismic excitation conditions.…”

Section: Introductionmentioning

confidence: 99%

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Numerical analysis for the vertical bearing capacity of composite pile foundation system in liquefiable soil under sine wave vibration

Huang

Yin

et al. 2021

PLoS ONE

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Composite pile foundation has been widely used in ground engineering. This composite pile foundation system has complex pile-soil interactions under seismic loading. The calculation of vertical bearing capacity of composite pile foundation is still an unsolved problem if the soil around piles is partially or completely liquefied under seismic loading. We have completed indoor shaking table model tests to measure the vertical bearing capacity in a liquefiable soil foundation under seismic loading. This paper will use a numerical approach to analyze the change of this vertical bearing capacity under seismic loading. Firstly, the Goodman contact element is improved to include the Rayleigh damping. Such an improvement can well describe the reflection and absorption of seismic waves at the interface of soil and piles. Secondly, the Biot’s dynamic consolidation theory incorporated an elastoplastic model is applied to simulate the soil deformation and the generation and accumulation of pore water pressure under seismic loading. Thirdly, after verification with our indoor shaking table test data, this approach is used to investigate the effects of pile spacing on liquefaction resistance of the composite pile foundation in liquefiable soil. The time histories of pore water pressure ratio (PPR′) are calculated for the liquefiable soil and the vertical bearing capacity in partially liquefied soil is calculated and compared with our indoor shaking table test data at the 3D, 3.5D, 4D, 5D and 6D cases (D is the pile diameter). It is found that the pile spacing has some influence on the extent of soil liquefaction between piles. The vertical bearing capacity varies with liquefaction extent of inter-pile soil. The optimization of pile spacing varies with liquefaction extent. These results may provide some reference for the design of composite pile foundation under seismic loading.

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Section: Effect Of Pile Spacing On Pore Water Pressure At Different Dsupporting

confidence: 81%

Section: Introductionmentioning

confidence: 99%

Numerical analysis for the vertical bearing capacity of composite pile foundation system in liquefiable soil under sine wave vibration

Huang

Yin

et al. 2021

PLoS ONE

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“…Also, the low value of the shear wave velocity of the crust seems to play an important role in these deviations. The same also holds for the other two modes of oscillation [30,31].…”

Section: Comparison Of Cone and Bem Solutionssupporting

confidence: 53%

Seismic isolation of surface foundations exploiting the properties of natural liquefiable soil

Karatzia

Mylonakis

Bouckovalas³

2019

Soil Dynamics and Earthquake Engineering

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“…The vertical stiffness was modelled as a linear no-tension spring. However, the spring stiffness decreased linearly with an increase in r u from an initial value K v;I , corresponding to r u ¼ 0, to a residual value K v;res at r u ¼ 1, where the residual value was calculated based on Karatzia et al (2017) and a shear wave velocity for the liquefied soil of 30 m=s [15% of the initial value consistent with the range of 10%-30% provided by Karatzia et al (2017)]. The stiffness was calculated at each step by reading the r u time series from the center of the liquefiable layer in the free-field.…”

Section: Estimation Of Soil-foundation Interface Stiffnessmentioning

confidence: 99%

“…The stiffness was calculated at each step by reading the r u time series from the center of the liquefiable layer in the free-field. Original research by Karatzia et al (2017) assumed that the liquefiable layer had the same properties under the building as in the free-field, and this assumption is also made here and may under-or over-estimate the soil stiffness, as the presence of the building modifies pore pressure build up and confining stress. The change in the vertical stiffness was not intended to capture the liquefaction-induced settlement (which was modelled through vertical displacements at the spring ends and is typically driven by several mechanisms as well as vertical loading) as the spring deformation in the case study below was less than 2 mm.…”

Section: Estimation Of Soil-foundation Interface Stiffnessmentioning

confidence: 99%

Macromechanism Approach for Vulnerability Assessment of Buildings on Shallow Foundations in Liquefied Soils

Fonseca

Millen

Quintero

et al. 2023

J. Geotech. Geoenviron. Eng.

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The damage caused by seismic shaking and liquefaction-induced permanent ground deformation has conventionally been assessed as two separate problems often by different engineers. However, the two problems are inherently linked, since ground shaking causes liquefaction, and liquefaction-induced soil softening affects ground shaking. Modelling both problems within a single numerical model is complex for both the engineer and the software, and most finite element software only have the capabilities to address one of them. To improve the estimates of the seismic performance of buildings on liquefiable soil, a new sub-structuring approach is proposed called the macro-mechanism approach. This approach allows the soil-liquefaction-foundation-structure interaction to be considered in a series of sub-models accounting for the major nonlinear mechanisms of the system at a macro level. The proposed approach was implemented in the open-source finite element software OpenSees and then applied to a case study of a building where significant liquefaction-and shaking-induced damage was observed after the 1999 Mw 7.4 Kocaeli Earthquake. The case study building was also simulated using two different commercial software programs, the finite difference software FLAC, and the finite element software PLAXIS, by two different research teams. A comparison between the results from the macromechanism approach compared to full numerical models shows that the macro-mechanism approach can capture the extent of the foundation deformation and provide more realistic estimates of the building damage than full approaches since the FLAC and PLAXIS models consider elastic elements for the building.

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Equivalent-Linear Dynamic Stiffness of Surface Footings on Liquefiable Soil

Abstract: Abstract. The focus of the present study is upon the influence of liquefaction on the dynamic

Cited by 4 publications

References 20 publications

Numerical analysis for the vertical bearing capacity of composite pile foundation system in liquefiable soil under sine wave vibration

Numerical analysis for the vertical bearing capacity of composite pile foundation system in liquefiable soil under sine wave vibration

Seismic isolation of surface foundations exploiting the properties of natural liquefiable soil

Macromechanism Approach for Vulnerability Assessment of Buildings on Shallow Foundations in Liquefied Soils

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