Nonlinear vibration of pile groups under lateral loading

1992 ◽  
Vol 29 (4) ◽  
pp. 702-710 ◽  
Author(s):  
Hans H. Vaziri ◽  
Yingcai Han
Keyword(s):  
Dynamic Response ◽  
Nonlinear Vibration ◽  
Damping Ratio ◽  
Pile Group ◽  
Harmonic Excitation ◽  
Pile Groups ◽  
Plane Normal ◽  
Interaction Factors ◽  
Full Scale Tests ◽  
Measured Response

Dynamic response of a pile group, comprising six full-size cast-in-place reinforced concrete piles, is investigated under varying levels of lateral harmonic excitation in two directions: along a plane composed of three piles (X-direction) and along a plane normal to it composed of two piles (Y-direction). The measured response is compared with the theoretical predictions using the dynamic interaction factors approach. To account for the nonlinear response of the pile group using the theoretical model, provisions are made for yielding of soil around the piles by introducing the boundary-zone concept. It is shown that the proposed theory adequately captures the measured response of the pile group under both linear (weak excitation) and nonlinear (strong excitation) conditions. The study performed indicates that although the rocking stiffness of the pile group is strongly influenced by the number of piles along the direction of excitation, the horizontal stiffness remains virtually unaffected. The results obtained show that the stiffness and damping ratio of the pile group reduce as the excitation intensity increases. It is also found that the pile–soil–pile interaction plays a major role in the overall dynamic response of the pile group; this effect is manifested by a reduction in the stiffness and an increase in the damping of the pile group. Key words : dynamics, vibration, piles, pile group, nonlinear vibration, full-scale tests, modelling, resonance, soil separation, soil yielding.

scholarly journals Flexible Pile Group Interaction Factors under Arbitrary Lateral Loading in Sand

2020 ◽  
Vol 8 (10) ◽  
pp. 800
Author(s):  
Miloš Marjanović ◽  
Mirjana Vukićević ◽  
Diethard König
Keyword(s):  
Numerical Study ◽  
Group Interaction ◽  
Pile Group ◽  
Lateral Loading ◽  
Soil Conditions ◽  
Offshore Platforms ◽  
Lateral Loads ◽  
Pile Groups ◽  
Main Hypothesis ◽  
Interaction Factors

Marine and harbor structures, wind turbines, bridges, offshore platforms, industrial chimneys, retaining structures etc. can be subjected to significant lateral loads from various sources. Appropriate assessment of the foundations capacity of these structures is thus necessary, especially when these structures are supported by pile groups. The pile group interaction effects under lateral loading have been investigated intensively in past decades, and the most of the conducted studies have considered lateral loading that acts along one of the two orthogonal directions, parallel to the edge of pile group. However, because of the stochastic nature of its source, the horizontal loading on the pile group may have arbitrary direction. The number of studies dealing with the pile groups under arbitrary loading is very limited. The aim of this paper is to investigate the influence of the arbitrary lateral loading on the pile group response, in order to improve (extend) the current design approach for laterally loaded pile groups. Free head, flexible bored piles in sand were analyzed through the extensive numerical study. The main hypothesis of the research is that some critical pile group configurations, loading directions, and soil conditions exist, which can lead to the unsafe structural design. Critical pile positions inside the commonly used pile group configurations are identified with respect to loading directions. The influence of different soil conditions was discussed.

Stiffness constants and interaction factors for vertical response of pile groups

1990 ◽  
Vol 27 (6) ◽  
pp. 813-822 ◽  
Author(s):  
Bahaa El Sharnouby ◽  
Milos Novak
Keyword(s):  
Group Analysis ◽  
Pile Group ◽  
Soil Parameters ◽  
Pile Groups ◽  
Continuous Transition ◽  
Interaction Factor ◽  
Wide Range ◽  
Interaction Factors ◽  
New Type ◽  
Single Piles

Stiffness constants and flexibility coefficients of single piles and interaction factors are presented to facilitate the analysis of pile groups subjected to static vertical loads. A continuous transition from friction to end-bearing piles is accounted for. A new type of interaction factor, established from subgroups of five piles, is introduced for end-bearing piles. This interaction factor allows for the stiffening effect of the piles occurring between the two reference piles. This feature improves the accuracy of group analysis for end-bearing piles. Numerical results for axially loaded single piles and pile groups are presented for a wide range of pile and soil parameters. The results are applicable toboth rigid and flexible caps. Key words: piles, pile group, settlement, interaction

The Vibration of Pile Groups Embedded in a Layered Poroelastic Half Space Subjected to Harmonic Axial Loads by Using Integral Equations Method

2012 ◽  
Vol 204-208 ◽  
pp. 1170-1173
Author(s):  
Chun Bo Cheng ◽  
Man Qing Xu ◽  
Bin Xu
Keyword(s):  
Dynamic Response ◽  
Layer Thickness ◽  
Integral Equations ◽  
Half Space ◽  
Pile Group ◽  
Dynamic Interaction ◽  
Fredholm Integral Equations ◽  
Pile Groups ◽  
Axial Loads ◽  
Layered Half Space

The dynamic response of a pile group embedded in a layered poroelastic half space subjected to axial harmonic loads is investigated in this study. Based on Biot's theory and utilizing Muki's method, the second kind of Fredholm integral equations describing the dynamic interaction between the layered half space and the pile group is constructed. Numerical results show that in a two-layered half space, for the closely populated pile group with a rigid cap, the upper softer layer thickness has considerably different influence on the center pile and the corner piles, while for sparsely populated pile group, it has almost the same influence on all the piles.

Flexibility coefficients and interaction factors for pile group analysis

1986 ◽  
Vol 23 (4) ◽  
pp. 441-450 ◽  
Author(s):  
Bahaa El Sharnouby ◽  
Milos Novak
Keyword(s):  
Load Distribution ◽  
Group Analysis ◽  
Vertical Plane ◽  
Ground Surface ◽  
Pile Group ◽  
Lateral Loads ◽  
Pile Groups ◽  
Group Evaluation ◽  
Interaction Factors ◽  
Single Piles

Flexibility coefficients of single piles and interaction factors established for groups of two piles are presented to facilitate analysis of arbitrary pile groups exposed to static horizontal loads. Such an analysis may yield pile group flexibility, stiffness, deflection, and distribution of loads on individual piles. The data given are complete in that they include horizontal translation, rotation in the vertical plane, and cross effects between the two, making it possible to establish complete stiffness and flexibility matrices of pile groups provided with either rigid caps or arbitrarily flexible caps. Homogeneous, parabolic, and linear (Gibson's) soil profiles are considered and the piles may have a free length sticking above the ground surface. The methods of group evaluation based on superposition of interaction factors are reviewed and compared and numerical examples are given. Key words: piles, pile groups, lateral loads, flexibility, stiffness, load distribution.

scholarly journals Numerical Investigation of the Dynamic Response of Symmetric Laminated Composite Beams to Harmonic Excitations

2009 ◽  
Vol 18 (5) ◽  
pp. 096369350901800 ◽  
Author(s):  
Zeki Kıral
Keyword(s):  
Dynamic Response ◽  
Frequency Response ◽  
Flexural Rigidity ◽  
Plate Theory ◽  
Damping Ratio ◽  
Excitation Frequency ◽  
Laminated Composite ◽  
Harmonic Excitation ◽  
Numerical Results ◽  
Harmonic Response

The aim of this study is to investigate the dynamic response of a laminated composite beam subjected to a harmonic excitation by a numerical time integration method known as Newmark method. The finite element method based on the classical laminated plate theory is used in order to obtain structural stiffness. The structural damping is modelled as proportional damping which is referred to as Rayleigh damping and two different damping ratios are used. The effect of damping on the frequency response of the beam is investigated for a broad range of excitation frequency. The effect of excitation point on the harmonic response is also considered. Four different lay-up configurations namely [0]2s, [0/90]s, [45/-45]s and [90]2s are considered in order to show the effect of the stacking sequence on the frequency response of the beam. The numerical results presented in this study show that, the magnitude of the harmonic response of the beam reduces considerably as the damping ratio increases and [90]2s lay-up produces largest dynamic response due to the reducing flexural rigidity. Numerical results also show that the location and frequency of the harmonic excitation has important role on the dynamic response of the beam.

scholarly journals Nonlinear vibration of knitted spacer fabric under harmonic excitation

2020 ◽  
Vol 15 ◽  
pp. 155892502098356
Author(s):  
Fuxing Chen ◽  
Hong Hu
Keyword(s):  
Nonlinear Vibration ◽  
Harmonic Balance Method ◽  
Harmonic Excitation ◽  
Polyurethane Foams ◽  
Excitation Level ◽  
Harmonic Amplitude ◽  
Damping Force ◽  
Spacer Fabric ◽  
Fabric System ◽  
Quadratic Stiffness

Knitted spacer fabrics can be an alternative material to typical rubber sponges and polyurethane foams for the protection of the human body from vibration exposure, such as automotive seat cushions and anti-vibration gloves. To provide a theoretical basis for the understanding of the nonlinear vibration behavior of the mass-spacer fabric system under harmonic excitation, experimental, analytical and numerical methods are used. Different from a linear mass-spring-damper vibration model, this study builds a phenomenological model with the asymmetric elastic force and the fractional derivative damping force to describe the periodic solution of the mass-spacer fabric system under harmonic excitation. Mathematical expression of the harmonic amplitude versus frequency response curve (FRC) is obtained using the harmonic balance method (HBM) to solve the equation of motion of the system. Parameter values in the model are estimated by performing curve fit between the modeled FRC and the experimental data of acceleration transmissibility. Theoretical analysis concerning the influence of varying excitation level on the FRCs is carried out, showing that nonlinear softening resonance turns into nonlinear hardening resonance with the increase of excitation level, due to the quadratic stiffness term and the cubic stiffness term in the model, respectively. The quadratic stiffness term also results in biased vibration response and causes an even order harmonic distortion. Besides, the increase of excitation level also results in elevated peak transmissibility at resonance.

Response of Liquid in Cylindrical Tank with Rigid Annual Baffle Considering Damping Effect

2011 ◽  
Vol 255-260 ◽  
pp. 3687-3691 ◽  
Author(s):  
Jia Dong Wang ◽  
Ding Zhou ◽  
Wei Qing Liu
Keyword(s):  
Free Surface ◽  
Dynamic Response ◽  
Potential Function ◽  
Natural Frequencies ◽  
Damping Ratio ◽  
Cylindrical Tank ◽  
Generalized Coordinates ◽  
Damping Effect ◽  
Total Potential ◽  
Free Surface Wave

Sloshing response of liquid in a rigid cylindrical tank with a rigid annual baffle under horizontal sinusoidal loads was studied. The effect of the damping was considered in the analysis. Natural frequencies and modes of the system have been calculated by using the Sub-domain method. The total potential function under horizontal loads is assumed to be the sum of the tank potential function and the liquid perturbed function. The expression of the liquid perturbed function is obtained by introducing the generalized coordinates. Substituting potential functions into the free surface wave conditions, the dynamic response equations including the damping effect are established. The damping ratio is calculated by Maleki method. The liquid potential are obtained by solving the dynamic response equations of the system.

Seismic Response of Pile Groups Improved with Deep Cement mixing Columns in Liquefiable Sand: Shaking Table Tests

2021 ◽  
Author(s):  
Dingwen Zhang ◽  
Anhui Wang ◽  
Xuanming Ding
Keyword(s):  
Seismic Behavior ◽  
Lateral Displacement ◽  
Bending Moment ◽  
Pile Group ◽  
Shaking Table ◽  
Excess Pore Pressure ◽  
Shaking Table Tests ◽  
Pile Groups ◽  
Acceleration Response ◽  
Table Model

A series of shaking table model tests were performed to examine the effects of deep cement mixing (DCM) columns with different reinforcement depths on the seismic behavior of a pile group in liquefiable sand. Due to the DCM column reinforcement, the fundamental natural frequency of the model ground increases noticeably. The excess pore pressure of soils reduces with the increase of reinforcement depths of the DCM columns. Before liquefaction, the acceleration response of soils in the improved cases is obviously lower than that in the unimproved case, but the acceleration attenuation is greater after liquefaction in the unimproved case. Moreover, the lateral displacement of the superstructure, the settlement of the raft, and the bending moment of the piles in the improved cases are significantly reduced compared to those in the unimproved case, and the reduction ratios rise with the increase of reinforcement depth of the DCM columns. However, reinforcement by the DCM columns may result in the variation of the location of the maximum moment that occurs in the pile.

scholarly journals Comparison of Induced Deflection and Forces in Piles Adjacent to Tunnelling and Deep Excavation in 2D and 3D Problems

2018 ◽  
Vol 203 ◽  
pp. 04011
Author(s):  
Ong Yin Hoe ◽  
Hisham Mohamad
Keyword(s):  
Bending Moment ◽  
Pile Group ◽  
3D Models ◽  
Deep Excavation ◽  
Pile Groups ◽  
Out Of Plane ◽  
National University ◽  
Plane Direction ◽  
2D And 3D ◽  
2D Model

There is a trend in Malaysia and Singapore, engineers tend to model the effect of TBM tunneling or deep excavation to the adjacent piles in 2D model. In the 2D model, the pile is modelled using embedded row pile element which is a 1-D element. The user is allowed to input the pile spacing in out-of-plane direction. This gives an impression to engineers the embedded pile row element is able to model the pile which virtually is a 3D problem. It is reported by Sluis (2014) that the application of embedded pile row element is limited to 8D of pile length. It is also reported that the 2D model overestimates the axial load in pile and the shear force and bending moment at pile top and it is not realistic in comparison to 3D model. In this paper, the centrifuge results of single pile and 6-pile group - tunneling problem carried out in NUS (National University of Singapore) are back-analysed with Midas GTS 3D and a 2D program. In a separate case study, pile groups adjacent to a deep excavation is modelled by 3D and 2D program. This paper compares the deflection and forces in piles in 2D and 3D models.

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