Modal analysis of pile‐supported structures during seismic liquefaction

Lombardi, Doménico; Bhattacharya, Subhamoy

doi:10.1002/eqe.2336

Cited by 80 publications

(24 citation statements)

References 36 publications

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“…Overall, the stiffness of the test system in Model 2 was relatively great than that in Model 1. Lombardi and Bhattacharya (2014) indicated that the natural frequency reduced by 20%-25% and 50%-60% at partial and full liquefaction, and the damping ratio increased by approximately 20% and 50% at partial and full liquefaction, respectively. The modal parameters of structure are listed in Table 1 at different stages of liquefaction.…”

Section: Assessment Of Modal Parametersmentioning

confidence: 99%

“…According to the experimental results, the modal parameters of the pile-superstructure were calculated before liquefaction and investigated based on the previous study (Lombardi and Bhattacharya, 2014) at partial and full liquefaction of the sand stratums. This was done because the experiments were not performed with a higher amplitude of white noise.…”

Section: Assessment Of Modal Parametersmentioning

confidence: 99%

See 1 more Smart Citation

Responses of reinforced concrete pile group in two-layered liquefied soils: shake-table investigations

Tang

Ling

et al. 2015

J. Zhejiang Univ. Sci. A

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During earthquakes, the response of pile foundations in liquefiable sand reinforced by densification techniques is still a very complex dynamic soil-structure interaction problem. Two shake-table experiments were conducted to investigate the behavior of a reinforced concrete (RC) low-cap pile group embedded in liquefiable soils. Discussion is focused on the behavior of soil-pile-superstructure systems prior to and during liquefaction of the medium-dense and dense sand stratums, which are involved in restoring force characteristics at the superstructure and pile group effect. The test results demonstrated a stiffness reduction and dependent nonlinear behavior appearing in the liquefied medium-dense sand; however, an overall stiffening response was observed in liquefied dense sand. The pile group effect seemed insignificant in liquefied medium-dense sand, but was very significant in the liquefied dense sand.

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Section: Assessment Of Modal Parametersmentioning

confidence: 99%

Section: Assessment Of Modal Parametersmentioning

confidence: 99%

Responses of reinforced concrete pile group in two-layered liquefied soils: shake-table investigations

Tang

Ling

et al. 2015

J. Zhejiang Univ. Sci. A

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“…The effects induced by soil liquefaction increase the damping ratio, which can reach values as high as 20% (Lombardi and Bhattacharya, 2014).…”

Section: Dampingmentioning

confidence: 99%

“…Ductility may be significantly lower in liquefaction conditions (Lombardi and Bhattacharya, 2014). Displacement ductility demand is defined as the ratio of global frame displacement demand to the yield displacement.…”

Section: Ductilitymentioning

confidence: 99%

Seismic analysis of pile in liquefiable soil and plastic hinge

Rostami

Hytiris

Bhattacharya

et al. 2017

Geotechnical Research

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Liquefaction is one of the leading seismic actions that cause extensive damage to buildings and infrastructure during earthquakes. In many historic cases, plastic hinge formations in piles were observed at inexplicable locations. This project investigated the behaviour of piled foundations within soils susceptible to liquefaction by using numerical analysis carried out in Abaqus software in terms of plastic hinge development. Three different soil profiles were considered in this project that varied in the thickness of both the liquefiable and non-liquefiable layers, pile length and free-and fixed-head pile conditions. Modelling a single pile as a beam-column element carrying both axial and El Centro record earthquake loading produced results of the seismic behaviour of piles that could be assessed by force-based seismic design approaches. The displacements and deformations induced by dynamic loads were analysed for piles affected by liquefaction, and the results were used to demonstrate the pile capacity and discuss the damage patterns and location of plastic hinges. Parametric studies generally demonstrate that plastic hinge formation occurs at the boundaries of the liquefiable and non-liquefiable layers; however, the location can be affected by a variety of factors such as material properties, pile length and thickness of the liquefied soil layer.

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“…Based on these structural parameters, the acceleration required for the assessment of the base shear force can be determined from an idealised acceleration response spectrum, such as the one depicted in Figure . In a conventional force‐based design, the effects induced by soil liquefaction, namely lengthening in period and increase in damping ratio, which can reach value as high as 20%, see for example , have significant consequences on the assessment of the seismic demand imposed by the shaking. Lombardi & Bhattacharya concluded that the pseudo‐acceleration, and consequently the base‐shear force, that the structure would experience during liquefaction condition may be significantly lower than that experienced prior to liquefaction condition (see Figure ).…”

Section: Introductionmentioning

confidence: 99%

Evaluation of seismic performance of pile‐supported models in liquefiable soils

Lombardi

Bhattacharya

2016

Earthq Engng Struct Dyn

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SUMMARYThe seismic performance of four pile-supported models is studied for two conditions: (i) transient to full liquefaction condition, i.e. the phase when excess pore pressure gradually increases during the shaking; (ii) full liquefaction condition, i.e. defined as the state where the seismically induced excess pore pressure equalises to the overburden stress. The paper describes two complementary analyses consisting of an experimental investigation, carried out at normal gravity on a shaking table, and a simplified numerical analysis, whereby the soil-structure interaction (SSI) is modelled through non-linear Winkler springs (commonly known as p-y curves). The effects of liquefaction on the SSI are taken into account by reducing strength and stiffness of the non-liquefied p-y curves by a factor widely known as p-multiplier and by using a new set of p-y curves. The seismic performance of each of the four models is evaluated by considering two different criteria: (i) strength criterion expressed in terms of bending moment envelopes along the piles; (ii) damage criterion expressed in terms of maximum global displacement. Comparison between experimental results and numerical predictions shows that the proposed p-y curves have the advantage of better predicting the redistribution of bending moments at deeper elevations as the soil liquefies. Furthermore, the proposed method predicts with reasonable accuracy the displacement demand exhibited by the models at the full liquefaction condition. However, disparities between computed and experimental maximum bending moments (in both transient and full liquefaction conditions) and displacement demands (during transient to liquefaction condition) highlight the need for further studies.

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Modal analysis of pile‐supported structures during seismic liquefaction

Cited by 80 publications

References 36 publications

Responses of reinforced concrete pile group in two-layered liquefied soils: shake-table investigations

Responses of reinforced concrete pile group in two-layered liquefied soils: shake-table investigations

Seismic analysis of pile in liquefiable soil and plastic hinge

Evaluation of seismic performance of pile‐supported models in liquefiable soils

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