Centrifuge modelling of monopiles subjected to lateral loading

Published on Mar 14, 2018in Scientia Iranica1.435
路 DOI :10.24200/SCI.2018.20222
S. Darvishi Alamouti2
Estimated H-index: 2
(UT: University of Tehran),
Majid Moradi9
Estimated H-index: 9
(UT: University of Tehran),
Mohammad Reza Bahaari11
Estimated H-index: 11
(UT: University of Tehran)
Sources
Abstract
Monopiles are the most common foundation type used for fixed-bottom substructures in offshore wind installations. In an offshore environment, the predominant load is cyclic, which affects the stiffness and deformation properties of foundation systems, especially monopiles. To investigate the effect of cyclic loading on a short (rigid) steel monopile, a set of displacement-controlled 畏g laboratory tests were designed. This paper presents the procedure and results of eight centrifuge tests investigating monopile behaviour when subjected to lateral monotonic and cyclic loading. The general trend of monotonic response is in good agreement with the results of similar experimental studies, however, much softer behaviour was observed compared to the equivalent Winkler model on API p-y curves. The cyclic tests focused on the stiffness and deformation properties of a soil-pile system under fatigue loading. Increases, decreases or no changes in secant stiffness were observed depending on the regime of the applied cyclic displacements which are in contradiction to current design methodology where only cyclic degradation is assumed. Influence of load cycling on cyclic bending moments along the pile shaft was discussed and found to be of minor significance
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References19
Newest
#1K. Farahmand (UT: University of Tehran)H-Index: 1
#2Ali Lashkari (SUTECH: Shiraz University of Technology)H-Index: 15
Last. Abbas Ghalandarzadeh (UT: University of Tehran)H-Index: 18
view all 3 authors...
The large-strain undrained behavior of Firoozkuh No. 161 sand is studied. It is observed that type of sand behavior is significantly affected by relative density (i.e., void ratio), the initial value of mean principal effective stress, and the shear mode. For samples subjected to the mode of triaxial compression, a clear steady-state line in both the q-p and e-p planes was obtained. For extension tests, dilation was not terminated at the end of the tests. As a result, the steady-state line for t...
Source
#1Hongyu Qin (Flinders University)H-Index: 8
#2Wei Dong Guo (UOW: University of Wollongong)H-Index: 17
An experimental investigation was made into the response of piles in sand subjected to lateral cyclic loading. Seven instrumented model piles tests were conducted. Five tests were conducted under typical magnitude and number of cyclic loading, and two were under static loading. The results were used to deduce modulus of subgrade reaction k and the profile of limiting lateral resistance force per unit length (LFP, pu profile) in light of closed-form solutions. The study demonstrates a large impac...
Source
In this paper, the authors present the results of field tests on a single laterally loaded pile and two piles in line. Bored reinforced concrete piles with a diameter of 0路25鈥塵 and a depth of 5鈥塵 were constructed in natural sandy gravels. The lateral loading on a head of tested piles is applied using a hydraulic press with a maximum force of 500鈥塳N. A single pile and two piles in line were incrementally loaded with a controlled head displacement of 2鈥塵m until the ultimate capacity of the pile wa...
Source
This paper deals with three different and important issues for centrifuge testing on monopiles for offshore wind turbines. A series of centrifuge model tests has been conducted on cylindrical stiff model monopiles that were installed at 1g and in-flight before being loaded laterally as well as on conical model piles installed in-flight. All model tests were performed in normally consolidated dense dry sand, simulating drained conditions. The tests confirmed three important issues for centrifuge ...
Source
#1Etienne A. Alderlieste (TU Delft: Delft University of Technology)H-Index: 1
#2Jelke Dijkstra (TU Delft: Delft University of Technology)H-Index: 10
Last. A. Frits van Tol (TU Delft: Delft University of Technology)H-Index: 4
view all 3 authors...
This paper presents the results of model tests on laterally loaded mono-pile foundations in sand. The tests have been performed in a geotechnical centrifuge. The objective of the research is to quantify large diameter effects of these mono-piles on the lateral capacity and the stiffness response for cyclic lateral loading. These large diameters are out of the validity range of the commonly used design methods. For this reason prototype pile diameters up to 4.4 m with a length over diameter ratio...
Source
#3Van Thien Mai (RyeU: Ryerson University)H-Index: 4
#4Ralph Dimaano (RyeU: Ryerson University)H-Index: 1
A sand displacement field around a laterally loaded pile is measured using an image processing technique called digital image correlation. An optical system consisting of a camera, a loading frame, and a computer is developed to capture soil movement during laterally loading the pile. Two images, before and after a deformation, are used to calculate the soil displacement field. Two kinds of piles are used in the tests: one squared-section pile and the other a circular one. Dry loose sand samples...
Source
#2Caspar Thrane LethH-Index: 2
Last. Ole HededalH-Index: 8
view all 3 authors...
A total number of 9 monotonic and 6 cyclic centrifuge tests on laterally loaded piles in very dense, dry sand was performed. The prototype dimensions of the piles were 1 meter in diameter and penetration depths varying from 6 to 10 meters. The static tests were used to investigate the initial subgrade reaction modulus and as a reference for cyclic tests. For the cyclic tests the accumulation of deflections and the change in secant stiffness of the soil from repetitive loading were investigated. ...
Source
#3BoltonH-Index: 2
Mono-pile foundations are widely used for wind turbines at present. They are always subjected to significant cyclic lateral loads due to wind and wave actions. In order to better understand the performance of mono-piles under cyclic lateral loads, a series of cyclic lateral load tests was conducted on a stainless steel mono-pile in the centrifuge. The axial and lateral responses of a large diameter mono-pile under one-way force-controlled cyclic lateral loads are described. Accumulated permanent...
Source
#1Ole HededalH-Index: 8
Modeling the response of large diameter piles subjected to lateral loading is most often done by means of p-y-curves in combination with Winkler beam models. Traditionally the p-y curves are formulated as non-linear (elastic) relations between the lateral movement y and the soil response pressure p in terms of monotonic loading (until failure) as e.g. prescribed byAPI (2000). However, the cyclic and dynamic performance is only to a limited degree accounted for. Here the elasto-plastic framework ...
Source
#1Nina H. Levy (WorleyParsons)H-Index: 4
#2Itai Einav (USYD: University of Sydney)H-Index: 32
Last. Tim Hull (GHD Group)H-Index: 1
view all 3 authors...
Pile foundations are frequently subjected to cyclic lateral loads. Wave and wind loads on offshore structures will be applied in different directions and times during the design life of a structure. Therefore, the magnitude and direction of these loads in conjunction with the dead loads should be considered. This paper investigates a loading scenario where a monotonic lateral load is applied to a pile, followed by two-way cycling in a direction perpendicular to the initial loading. This configur...
Source
Cited By2
Newest
#1Roozbeh Rezanejad Malakshah (UT: University of Tehran)
#2Majid Moradi (UT: University of Tehran)H-Index: 9
Last. Abbas Ghalandarzadeh (UT: University of Tehran)H-Index: 18
view all 3 authors...
Monopiles are the most common foundation type for offshore wind turbines. These structures are subjected to millions of cyclic horizontal loads during their lifespans, mainly from waves and wind; however, there are gaps in conventional design methods for different aspects of cyclic loading. The present study examined the cyclic behaviour of monopiles in dry calcareous sand. Centrifuge tests were carried out to investigate the effect of cyclic loading on the accumulated displacement and soil-pile...
Source
#1A. Faresghoshooni (AUT: Amirkabir University of Technology)
#2S. M. R. Imam (AUT: Amirkabir University of Technology)
Last. A. Mahmoodi (AUT: Amirkabir University of Technology)
view all 3 authors...
In this study, two-way cyclic lateral loading tests with constant displacement amplitude are performed to investigate the effect of cross section geometry and modulus of elasticity on the behavior of model piles in sand. Various laboratory pile models were tested in a metal test tank equipped with various facilities including cyclic lateral loading system, devices to measure displacement and pressure along the pile, an inverter to adjust or change loading frequency, sand raining system, etc. Dif...
Source
#1S. Darvishi Alamouti (UT: University of Tehran)H-Index: 2
#2Mohammad Reza Bahaari (UT: University of Tehran)H-Index: 11
Last. Majid Moradi (UT: University of Tehran)H-Index: 9
view all 3 authors...
Monopiles supporting offshore wind turbines are commonly designed using p鈥搚 curves that are originally validated for slender piles in oil and gas applications. In this study, it is aimed to...
Source
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