scholarly journals The Effect of Vertical Loads and the Pile Shape on Pile Group Response under Lateral Two-Way Cyclic Loading

2019 ◽  
Vol 5 (11) ◽  
pp. 2377-2391
Author(s):  
Aseel Kahlan Mahmood ◽  
Jasim M Abbas
Keyword(s):  
Cyclic Loading ◽  
Cyclic Load ◽  
Lateral Displacement ◽  
Load Ratio ◽  
Pile Group ◽  
Pile Groups ◽  
Group Response ◽  
Load Intensity ◽  
Number Of Cycles ◽  
Aluminum Pipe

This paper is presented the lateral dynamic response of pile groups embedded in dry sand under influence of vertical loads and the pile shape in-group, which are subjected to the lateral two-way cyclic loads. The laboratory typical tests with pile groups (2×1) have an aluminum-pipe (i.e. circular, square) pile, embedded length to diameter of pile ratio (L/D=40) and spacing to diameter ratio (S/D) of 3, 5, 7 and 9 are used with different cyclic-load ratio (CLR) 0.4, 0.6 and 0.8. The experimental results are revealed that both the vertical and lateral pile capacity and displacement is significantly affected by the cyclic-loading factors i.e. (number of cycles, cyclic load ratio, and shape of pile) .In this study, important design references are presented. Which are explained that the response of the pile groups under cyclic lateral loading are clear affected by the attendance of vertical load and pile shape. Where, it is reduction the lateral displacement of group piles head and increase lateral capacity about (50) % compared without vertical loads. On the other side, the pile shape is a well affected to the pile response where the level of decline in lateral displacement at the pile groups head in the square pile is more than circular pile about 20 % at the same load intensity.

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.

Pile group elastic load response prediction: friction piles embedded in cohesive soils

1984 ◽  
Vol 21 (3) ◽  
pp. 587-592
Author(s):  
R. A. Douglas ◽  
R. Butterfield
Keyword(s):  
Design Procedure ◽  
Pile Group ◽  
Response Prediction ◽  
Reduction Factor ◽  
Cohesive Soils ◽  
Pile Groups ◽  
Elastic Load ◽  
Stiffness Reduction ◽  
Load Response ◽  
Group Response

Predicting the elastic vertical working load response of friction pile groups embedded in cohesive soils is a problem still requiring a solution that can be easily implemented by practising engineers. A design procedure based on an extensive analysis of the results of a computer program is presented as a solution to the problem.The program was used to study the effects of the interaction of closely spaced piles in groups, on the pile group response to loading. It is possible to define an average pile stiffness (load per unit displacement) and discuss a reduction of this stiffness, due to pile interaction, when the pile is placed in a group of similar piles. This interaction is accounted for by a stiffness reduction factor, ρ.The design approach is compared with load tests at model and full scale, with good agreement. Key words: piles, pile groups, working loads, elastic pile displacements.

scholarly journals Vertical cyclic loading response of shallow skirted foundation in soft normally consolidated clay

2019 ◽  
Vol 56 (4) ◽  
pp. 473-483 ◽  
Author(s):  
Dimitra Zografou ◽  
Susan Gourvenec ◽  
Conleth O’Loughlin
Keyword(s):  
Steady State ◽  
Cyclic Loading ◽  
Threshold Stress ◽  
Cyclic Load ◽  
Vertical Displacement ◽  
Offshore Structures ◽  
Kaolin Clay ◽  
Centrifuge Tests ◽  
Number Of Cycles ◽  
Mode A

Skirted foundations are a potential foundation solution for a range of offshore structures, including hydrocarbon and renewable energy platforms and subsea structures. Offshore foundations can be subject to cyclic loading from environmental, installation, and operational events affecting the geotechnical response. A series of centrifuge tests have been performed on a shallow skirted foundation on normally consolidated kaolin clay under a range of vertical cyclic load sequences to investigate the effect of tensile or compressive average stress, the magnitude of the applied stress, and the effect of cyclic loading of low magnitude followed by consolidation on the foundation response. Results are presented as vertical foundation displacements normalized by the foundation geometry and interpreted within the traditional shear-strain contour approach. The findings indicate that the average, rather than maximum, vertical stress defines the foundation vertical displacement response and failure mode, a threshold stress exists below which a steady state is maintained even at a high number of cycles, and geotechnical resistance increases as a result of low-level cyclic loading followed by consolidation.

scholarly journals Investigation of piles behavior under lateral cyclic load

2019 ◽  
Vol 39 (3) ◽  
pp. 213-220
Author(s):  
Chunhui Liu ◽  
Liang Tang ◽  
Xianzhang Ling
Keyword(s):  
Cyclic Load ◽  
Pile Group ◽  
Nonlinear Finite Element ◽  
Lateral Loading ◽  
Finite Element Models ◽  
Soil System ◽  
Pile Spacing ◽  
Practical Engineering ◽  
Number Of Cycles ◽  
Pile Group Effect

In this paper, the capability of 3D nonlinear finite element models is validated by single pile and 5x3 pile group filed experiments that is subjected to cyclic lateral loading. Then, a series 3D finite elements models are built to analyze the effect of the number of cycles of lateral loading, pile spacing, and pile group arrangement. The results have shown that the number of cycles affected the pile-soil system stiffness seriously, and the pile group effect became insignificant as the increase of pile spacing, while this effect became more significant with the increase of the pile group arrangement. In practical engineering, the pile spacing and pile group arrangement should be considered and chosen carefully.

scholarly journals Effect of Cyclic Loading on the Lateral Behavior of Offshore Monopiles Using the Strain Wedge Model

2015 ◽  
Vol 2015 ◽  
pp. 1-12 ◽  
Author(s):  
Keunju Kim ◽  
Boo Hyun Nam ◽  
Heejung Youn
Keyword(s):  
Cyclic Loading ◽  
Lateral Displacement ◽  
Triaxial Compression ◽  
Lateral Loads ◽  
Compression Tests ◽  
Initial Stiffness ◽  
Quartz Sands ◽  
Number Of Cycles ◽  
Lateral Behavior ◽  
Strain Wedge

This paper presents the effect of cyclic loading on the lateral behavior of monopiles in terms of load-displacement curves, deflection curves, andp-ycurves along the pile. A commercial software, Strain Wedge Model (SWM), was employed, simulating a 7.5 m in diameter and 60 m long steel monopile embedded into quartz sands. In order to account for the effect of cyclic loading, accumulated strains were calculated based on the results of drained cyclic triaxial compression tests, and the accumulated strains were combined with static strains representing input strains into the SWM. The input strains were estimated for different numbers of cycles ranging from 1 to 105and 3 different cyclic lateral loads (25%, 50%, and 75% of static capacity). The lateral displacement at pile head was found to increase with increasing number of cycles and increasing cyclic lateral loads. In order to model these deformations resulting from cyclic loading, the initial stiffness of thep-ycurves has to be significantly reduced.

Numerical Analysis of a Strip With a Hole Subjected to Cyclic Loading

1990 ◽  
Vol 112 (4) ◽  
pp. 471-476
Author(s):  
H. Ishikawa ◽  
K. Sasaki
Keyword(s):  
Numerical Analysis ◽  
Cyclic Loading ◽  
Cyclic Load ◽  
Mean Value ◽  
304 Stainless Steel ◽  
Mean Values ◽  
Nonzero Mean ◽  
Number Of Cycles ◽  
Type 304 ◽  
Type 304 Stainless Steel

This paper deals with the problem of a strip with a hole subjected to cyclic loading at the ends. For the numerical analysis, a constitutive model incorporating the motion of the center of the yield surface is implemented in a finite element method. The distributions of strain and stress during cyclic loading are discussed in detail both for the zero and nonzero mean values of cyclic load. To verify the results of the computer simulation, an experiment on a strip with a hole of type 304 stainless steel is carried out. Results of the experiment show that during cyclic loading with nonzero mean value of cyclic load, strain at the bottom of the circular hole is ratchetted with increase in number of cycles, and the stress approaches that due to the zero mean value of cyclic load.

scholarly journals A model test study on the parameters affecting the cyclic lateral response of monopile foundations for offshore wind turbines embedded in non-cohesive soils

2021 ◽  
Author(s):  
Dennis Frick ◽  
Martin Achmus
Keyword(s):  
Cyclic Loading ◽  
Model Test ◽  
Wind Turbines ◽  
Cyclic Load ◽  
Prediction Models ◽  
Load Ratio ◽  
Offshore Wind ◽  
Small Scale ◽  
Parameter Study ◽  
Offshore Wind Turbines

Abstract. During their service life, monopiles supporting offshore wind turbines are subjected to large numbers of lateral cyclic loads resulting from complex environmental conditions such as wind and waves varying in amplitude, direction, load eccentricity and frequency. The consequential accumulation of displacements and rotations of the foundation structure with cyclic loading is one key concern in the design of monopiles. Nevertheless, the relevant offshore guidelines do not provide suitable procedures for predicting such deformations. Although there are several methods for this purpose in literature, some of them produce very different or even contradictory results, which prevents a consistent approach to dimensioning. This paper briefly summarizes the current standardization regarding design of monopiles for cyclic lateral loading and provides some examples of possible prediction models from the literature. To highlight the need for further research, the predictions according to different approaches are compared and evaluated by a calculation example and a parameter study. Further, the results of a small-scale 1 g model test campaign on the load-displacement behaviour of monopile foundations subjected to lateral cyclic loading and the influencing parameters are presented, evaluated and compared with the findings of other research groups. In this way the tests results can help to support or improve model development and provide insight into key issues relevant to monopile design. The parameters that have been assessed include the cyclic load magnitude, cyclic load ratio, load eccentricity, soil relative density, the grain size distribution of the non-cohesive bedding material as well as the pile embedment length.

Cyclic axial behaviour of piles and pile groups in sand

2012 ◽  
Vol 49 (9) ◽  
pp. 1074-1087 ◽  
Author(s):  
Zheming Li ◽  
Malcolm D. Bolton ◽  
Stuart K. Haigh
Keyword(s):  
Axial Load ◽  
Pile Group ◽  
Offshore Structures ◽  
Pile Groups ◽  
Axial Loads ◽  
Bored Pile ◽  
Load Cycling ◽  
Permanent Settlement ◽  
Number Of Cycles ◽  
Piled Foundations

Piled foundations are often subjected to cyclic axial loads. This is particularly true for the piles of offshore structures, which are subjected to rocking motions caused by wind or wave actions, and for those of transport structures, which are subjected to traffic loads. As a result of these cyclic loads, excessive differential or absolute settlements may be induced during the piles’ service life. In the research presented here, centrifuge modelling of single piles and pile groups was conducted to investigate the influence of cyclic axial loads on the performance of piled foundations. The influence of installation method was investigated and it was found that the cyclic response of a pile whose jacked installation was modelled correctly is much stiffer than that of a bored pile. During displacement-controlled axial load cycling, the pile head stiffness reduces with an increasing number of cycles, but at a decreasing rate; during force-controlled axial load cycling, more permanent settlement is accumulated for a bored pile than for a jacked pile. The performance of individual piles in a pile group subjected to cyclic axial loads is similar to that of a single pile, without any evident group effect. Finally, a numerical analysis of axially loaded piles was validated by centrifuge test results. Cyclic stiffness of soil at the base of pre-jacked piles increases dramatically, while at base of jacked piles it remains almost constant.

Coefficients of Settlement and Lateral Displacement in Pile Group during Tunneling

2012 ◽  
Vol 594-597 ◽  
pp. 1343-1346
Author(s):  
Li Wang ◽  
Gang Zheng
Keyword(s):  
Finite Element ◽  
Finite Element Methods ◽  
Lateral Displacement ◽  
Pile Group ◽  
Finite Element Models ◽  
Group Effect ◽  
Pile Groups ◽  
Centrifuge Tests ◽  
Sheltering Effect ◽  
Couple Effect

Finite element methods are adopted herein to study the group effect and sheltering effect in pile group during shield driven when the couple effect of vertical loads and soil displacement is considered. Results from the FEM show fine agreement with those from the Tianjin No.1 subway line project and the centrifuge tests carried out by Loganathan. Based on the finite element models, the effects of tunneling on pile groups are studied. The coefficients of settlement and lateral displacement are defined to assess the group effect and sheltering effect in pile groups with elevated cap.

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