Experimental investigation of kinematic pile bending in layered soils using dynamic centrifuge modelling

Garala, Thejesh Kumar; Madabhushi, Spg; Laora, Raffaele Di

doi:10.1680/jgeot.19.p.185

Cited by 21 publications

(22 citation statements)

References 21 publications

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“…The results of this study extend, therefore, the validity of the simple analytical solutions to the non-linear range of soil response, denoting that kinematic soil-pile interaction is controlled by the soil stiffness even if the response of the soil is controlled by its strength. The above finding generalizes earlier indications [27][28][29][30] of the controlling role of the mobilized soil stiffness on pile kinematic bending.…”

Section: Frequency Effects: Proposed Analytical Expressionsupporting

confidence: 90%

Kinematic Pile-Head Bending Under Large Earthquake-Induced Shear Strains

Stacul¹,

Rovithis²,

Laora³

2021

Proceedings of the 8th International Conference on Computational Methods in Structural Dynamics and Earthquake Engineering (COM

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The problem of kinematic bending moments imposed at the head of a single pile during the passage of seismic waves is explored under large shear strains in the surrounding soil. To this end, non-linear soil response at free-field conditions is derived numerically by a freelyavailable 1D code and then utilized to calibrate the constitutive law of soil introduced in a rigorous 3D Finite-Difference (FD) model of the soil-pile system employed to obtain pile's head bending moments. The pile is considered embedded to a normally-consolidated clay and seven earthquake records with different amplitude and frequency content are imposed as input motions at the base of the soil layer, thus allowing the investigation of pile kinematic bending with increasing levels of shear strains in the soil, exceeding the limit of equivalentlinear soil behavior. The performance of a simple analytical expression for predicting the kinematic bending moment at the pile-head is compared to the rigorous FD solution. It is concluded that this simple solution is still applicable, with slight modifications, for high shear strains related to non-linear soil behavior close to shear failure, provided that the proper mobilized soil properties from 1D soil response analysis are introduced.

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Section: Frequency Effects: Proposed Analytical Expressionsupporting

confidence: 90%

Kinematic Pile-Head Bending Under Large Earthquake-Induced Shear Strains

Stacul¹,

Rovithis²,

Laora³

2021

Proceedings of the 8th International Conference on Computational Methods in Structural Dynamics and Earthquake Engineering (COM

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“…Centrifuge modelling can be used to eliminate these scaling issues by allowing full-scale stress levels to exist within a small-scale model [ 25 ]. This technique has previously been used to examine the dynamic response of monopile models representing offshore wind turbines but not to examine the dynamic behaviour of bridges [ 26 , 27 ].…”

Section: Introductionmentioning

confidence: 99%

Assessment of bridge natural frequency as an indicator of scour using centrifuge modelling

Kariyawasam

Middleton

Madabhushi

et al. 2020

J Civil Struct Health Monit

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One of the most prevalent causes of bridge failure around the world is "scour"-the gradual erosion of soil around a bridge foundation due to fast-flowing water. A reliable technique for monitoring scour would help bridge engineers take timely countermeasures to safeguard against failure. Although vibration-based techniques for monitoring structural damage have had limited success, primarily due to insufficient sensitivity, these have tended to focus on the detection of local damage. High natural frequency sensitivity has recently been reported for scour damage. Previous experiments to investigate this have been limited as a result of the cost of full-scale testing and the fact that scaled-down soil-structure models tested outside a centrifuge do not adequately simulate full-scale behaviour. This paper describes the development of what is believed to be the first-ever centrifuge-testing programme to establish the sensitivity of bridge natural frequency to scour. A 1/60 scale model of a two-span integral bridge with 15 m spans was tested at varying levels of scour. For the fundamental mode of vibration, these tests found up to a 40% variation in natural frequency for 30% loss of embedment. Models of three other types of foundation, which represent a shallow pad foundation, a deep pile bent and a deep monopile, were also tested in the centrifuge at different scour levels. The shallow foundation model showed lower frequency sensitivity to scour than the deep foundation models. Another important finding is that the frequency sensitivity to "global scour" is slightly higher than the sensitivity to "local scour", for all foundation types. The level of frequency sensitivity (3.1-44% per scour depth equivalent to 30% of embedment of scour) detected in this experiment demonstrates the potential for using natural frequency as an indicator of both local and global scour of bridges, particularly those with deep foundations.

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“…1c. Table 1 lists the properties of fraction-B LB sand (Garala et al 2020) and the properties of speswhite kaolin clay (Lau 2015) are given in Table 2.…”

Section: Methodsmentioning

confidence: 99%

“…The equations used for computing the G0 from literature methods can be found in Garala et al (2020).…”

Section: Model Preparation and Centrifuge Testingmentioning

confidence: 99%

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Influence of phase difference between kinematic and inertial loads on seismic behaviour of pile foundations in layered soils

Garala

Madabhushi

2020

Can. Geotech. J.

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A series of dynamic centrifuge experiments was conducted on model pile foundations embedded in a two-layered soil profile consisted of soft-clay layer underlain by dense sand. These experiments were specifically designed to investigate the individual effect of kinematic and inertial loads on a single pile and a 3×1 row pile group during model earthquakes. It was observed that the ratio of free-field soil natural frequency to the natural frequency of structure might not govern the phase relationship between the kinematic and inertial loads for pile foundations as reported in some previous research. The phase relationship obtained in this study agrees well with the conventional phase variation between the force and displacement of a viscously damped simple oscillator subjected to a harmonic force. Further, as expected, the pile accelerations and bending moments can be smaller when the kinematic and inertial loads act against each other compared to the case when they act together on the pile foundations. This study also revealed that the peak kinematic pile bending moment will be at the interface of soil layers for both single pile and pile group. However, in the presence of both kinematic and inertial loads, the peak pile bending moment can occur either at the shallower depths or at the interface of soil layers depending on the pile cap rotational constraint.

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Experimental investigation of kinematic pile bending in layered soils using dynamic centrifuge modelling

Cited by 21 publications

References 21 publications

Kinematic Pile-Head Bending Under Large Earthquake-Induced Shear Strains

Kinematic Pile-Head Bending Under Large Earthquake-Induced Shear Strains

Assessment of bridge natural frequency as an indicator of scour using centrifuge modelling

Influence of phase difference between kinematic and inertial loads on seismic behaviour of pile foundations in layered soils

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