Controlling cyclic stiffness of a foundation, by manipulating the deformation history

Publikation: Bidrag til tidsskriftTidsskriftartikelForskningpeer review

Resumé

Offshore wind turbines are slender structures, dynamic response of which depends on foundation stiffness. Unfortunately, foundations embedded in sand can become disturbed, their stiffness can increase and decrease episodically. To investigate the phenomenon governing loss and recovery of stiffness, an original testing program was implemented. A prototype of an offshore foundation was repeatedly disturbed and re-stabilized: the stiffness curve generated while testing peak strength was disturbed and reset back to initial state, multiple times, in one loading sequence.

The ability to reset the "initial stiffness path" was achieved after observing a new physical phenomenon: converging Stiffness hysteresis loops. During cycles of constant deformation amplitude, stiffness hysteresis loop were observed to converge in proportion to applied deformation amplitude. Thus, by controlling position and amplitude of deformation cycles, the stiffness hysteresis loops can be "stretched" and "repositioned" along the deformation axis. Therefore, allowing to de-facto control cyclic stiffness of a foundation - to disturb and reset the initial soil state. The observations provide new factual evidence, which suggests some features of cyclic stiffness in sand could be governed exclusively by deformation history. Furthermore, inputs adequate to control a phenomenon in practice, could be adequate to model the phenomenon in theory. Thus, the new observations could be a precursor to a new generation of numerical models.

The ability to reset the "initial stiffness path" was achieved after observing a new physical phenomenon: converging Stiffness hysteresis loops. During cycles of constant deformation amplitude, stiffness hysteresis loop were observed to converge in proportion to applied deformation amplitude. Thus, by controlling position and amplitude of deformation cycles, the stiffness hysteresis loops can be "stretched" and "repositioned" along the deformation axis. Therefore, allowing to de-facto control cyclic stiffness of a foundation - to disturb and reset the initial soil state. The observations provide new factual evidence, which suggests some features of cyclic stiffness in sand could be governed exclusively by deformation history. Furthermore, inputs adequate to control a phenomenon in practice, could be adequate to model the phenomenon in theory. Thus, the new observations could be a precursor to a new generation of numerical models.
OriginalsprogEngelsk
TidsskriftCanadian Geotechnical Journal
ISSN0008-3674
StatusAfsendt - 2019

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stiffness
History
Stiffness
history
Hysteresis loops
hysteresis
physical phenomena
Sand
sand
Numerical models
Offshore wind turbines
Soils
wind turbine
Testing
dynamic response
Dynamic response
soil

Emneord

  • Soil dynamics
  • Mono bucket
  • Deformation envelope
  • Strain space
  • Irregular loads
  • Offshore foundation

Citer dette

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title = "Controlling cyclic stiffness of a foundation, by manipulating the deformation history",
abstract = "Offshore wind turbines are slender structures, dynamic response of which depends on foundation stiffness. Unfortunately, foundations embedded in sand can become disturbed, their stiffness can increase and decrease episodically. To investigate the phenomenon governing loss and recovery of stiffness, an original testing program was implemented. A prototype of an offshore foundation was repeatedly disturbed and re-stabilized: the stiffness curve generated while testing peak strength was disturbed and reset back to initial state, multiple times, in one loading sequence.The ability to reset the {"}initial stiffness path{"} was achieved after observing a new physical phenomenon: converging Stiffness hysteresis loops. During cycles of constant deformation amplitude, stiffness hysteresis loop were observed to converge in proportion to applied deformation amplitude. Thus, by controlling position and amplitude of deformation cycles, the stiffness hysteresis loops can be {"}stretched{"} and {"}repositioned{"} along the deformation axis. Therefore, allowing to de-facto control cyclic stiffness of a foundation - to disturb and reset the initial soil state. The observations provide new factual evidence, which suggests some features of cyclic stiffness in sand could be governed exclusively by deformation history. Furthermore, inputs adequate to control a phenomenon in practice, could be adequate to model the phenomenon in theory. Thus, the new observations could be a precursor to a new generation of numerical models.The ability to reset the {"}initial stiffness path{"} was achieved after observing a new physical phenomenon: converging Stiffness hysteresis loops. During cycles of constant deformation amplitude, stiffness hysteresis loop were observed to converge in proportion to applied deformation amplitude. Thus, by controlling position and amplitude of deformation cycles, the stiffness hysteresis loops can be {"}stretched{"} and {"}repositioned{"} along the deformation axis. Therefore, allowing to de-facto control cyclic stiffness of a foundation - to disturb and reset the initial soil state. The observations provide new factual evidence, which suggests some features of cyclic stiffness in sand could be governed exclusively by deformation history. Furthermore, inputs adequate to control a phenomenon in practice, could be adequate to model the phenomenon in theory. Thus, the new observations could be a precursor to a new generation of numerical models.",
keywords = "Soil dynamics, Mono bucket, Deformation envelope, Strain space, Irregular loads, Offshore foundation, Soil dynamics, Mono bucket, Deformation envelope, Strain space, Irregular loads, Offshore foundation",
author = "Tomas Sabaliauskas and Ibsen, {Lars Bo}",
year = "2019",
language = "English",
journal = "Canadian Geotechnical Journal",
issn = "0008-3674",
publisher = "N R C Research Press",

}

Controlling cyclic stiffness of a foundation, by manipulating the deformation history. / Sabaliauskas, Tomas; Ibsen, Lars Bo.

I: Canadian Geotechnical Journal, 2019.

Publikation: Bidrag til tidsskriftTidsskriftartikelForskningpeer review

TY - JOUR

T1 - Controlling cyclic stiffness of a foundation, by manipulating the deformation history

AU - Sabaliauskas, Tomas

AU - Ibsen, Lars Bo

PY - 2019

Y1 - 2019

N2 - Offshore wind turbines are slender structures, dynamic response of which depends on foundation stiffness. Unfortunately, foundations embedded in sand can become disturbed, their stiffness can increase and decrease episodically. To investigate the phenomenon governing loss and recovery of stiffness, an original testing program was implemented. A prototype of an offshore foundation was repeatedly disturbed and re-stabilized: the stiffness curve generated while testing peak strength was disturbed and reset back to initial state, multiple times, in one loading sequence.The ability to reset the "initial stiffness path" was achieved after observing a new physical phenomenon: converging Stiffness hysteresis loops. During cycles of constant deformation amplitude, stiffness hysteresis loop were observed to converge in proportion to applied deformation amplitude. Thus, by controlling position and amplitude of deformation cycles, the stiffness hysteresis loops can be "stretched" and "repositioned" along the deformation axis. Therefore, allowing to de-facto control cyclic stiffness of a foundation - to disturb and reset the initial soil state. The observations provide new factual evidence, which suggests some features of cyclic stiffness in sand could be governed exclusively by deformation history. Furthermore, inputs adequate to control a phenomenon in practice, could be adequate to model the phenomenon in theory. Thus, the new observations could be a precursor to a new generation of numerical models.The ability to reset the "initial stiffness path" was achieved after observing a new physical phenomenon: converging Stiffness hysteresis loops. During cycles of constant deformation amplitude, stiffness hysteresis loop were observed to converge in proportion to applied deformation amplitude. Thus, by controlling position and amplitude of deformation cycles, the stiffness hysteresis loops can be "stretched" and "repositioned" along the deformation axis. Therefore, allowing to de-facto control cyclic stiffness of a foundation - to disturb and reset the initial soil state. The observations provide new factual evidence, which suggests some features of cyclic stiffness in sand could be governed exclusively by deformation history. Furthermore, inputs adequate to control a phenomenon in practice, could be adequate to model the phenomenon in theory. Thus, the new observations could be a precursor to a new generation of numerical models.

AB - Offshore wind turbines are slender structures, dynamic response of which depends on foundation stiffness. Unfortunately, foundations embedded in sand can become disturbed, their stiffness can increase and decrease episodically. To investigate the phenomenon governing loss and recovery of stiffness, an original testing program was implemented. A prototype of an offshore foundation was repeatedly disturbed and re-stabilized: the stiffness curve generated while testing peak strength was disturbed and reset back to initial state, multiple times, in one loading sequence.The ability to reset the "initial stiffness path" was achieved after observing a new physical phenomenon: converging Stiffness hysteresis loops. During cycles of constant deformation amplitude, stiffness hysteresis loop were observed to converge in proportion to applied deformation amplitude. Thus, by controlling position and amplitude of deformation cycles, the stiffness hysteresis loops can be "stretched" and "repositioned" along the deformation axis. Therefore, allowing to de-facto control cyclic stiffness of a foundation - to disturb and reset the initial soil state. The observations provide new factual evidence, which suggests some features of cyclic stiffness in sand could be governed exclusively by deformation history. Furthermore, inputs adequate to control a phenomenon in practice, could be adequate to model the phenomenon in theory. Thus, the new observations could be a precursor to a new generation of numerical models.The ability to reset the "initial stiffness path" was achieved after observing a new physical phenomenon: converging Stiffness hysteresis loops. During cycles of constant deformation amplitude, stiffness hysteresis loop were observed to converge in proportion to applied deformation amplitude. Thus, by controlling position and amplitude of deformation cycles, the stiffness hysteresis loops can be "stretched" and "repositioned" along the deformation axis. Therefore, allowing to de-facto control cyclic stiffness of a foundation - to disturb and reset the initial soil state. The observations provide new factual evidence, which suggests some features of cyclic stiffness in sand could be governed exclusively by deformation history. Furthermore, inputs adequate to control a phenomenon in practice, could be adequate to model the phenomenon in theory. Thus, the new observations could be a precursor to a new generation of numerical models.

KW - Soil dynamics

KW - Mono bucket

KW - Deformation envelope

KW - Strain space

KW - Irregular loads

KW - Offshore foundation

KW - Soil dynamics

KW - Mono bucket

KW - Deformation envelope

KW - Strain space

KW - Irregular loads

KW - Offshore foundation

M3 - Journal article

JO - Canadian Geotechnical Journal

JF - Canadian Geotechnical Journal

SN - 0008-3674

ER -