An Overview of Support Structure and Foundation System of Wind Turbines 20131120

8/12/2019 An Overview of Support Structure and Foundation System of Wind Turbines 20131120

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testing of wind turbines that are not only more efficient but also much larger than

those currently in use. These large turbines will place significant demands on their

support structures. The combination of greater water depths, increased tower

heights, and larger rotor diameters will impose loads that greatly complicate the

process of designing support structures.

An offshore wind turbine (OWT) is formed by both mechanical and structural

elements. Therefore, it is not a common civil engineering structure; it behaves

differently according to the different circumstances related to the specific

functional activity (parked, operation, etc), and it is subject to highly variable loads

(wind, wave, sea currents loads, etc.). In the design process, different structural

schemes for the supporting structure can be adopted (Figure X), mainly depending

on the water depth, which determines the hydrodynamic loads acting on the

structure and drives the choice of the proper techniques for the installation and

maintenance of the support structure [2].

As mentioned above, there are a variety of loads would be applied on the

support structure of an OWT. The load-induced vibration would lead to the

resonance of an OWT, and impose even greater demands on the design of the

support structures. Accordingly, the support structure systems would need to be

made relatively stiff. However, a stiffer foundation will require more materials and

therefore will cost more than a flexible foundation. Figure X shows all common

type of the support structures systems.

Figure [7]: Types of foundation and support structures of wind turbine system



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2. OWT System

I. Classification[Ref]

With advantages of the system approach applied to OWT design, the

whole structural system could be decomposed. Figure 1 shows the overview

of the system, and Figure 3 shows the system hierarchy.

Figure 1: Main parts of an offshore wind turbine for different support structures



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Figure 3[2]: Offshore wind turbine structural system decomposition

Since the structural behavior of OWTs is influenced from nonlinearities,

uncertainties and interactions, they can be defined as complex structural

systems. This system approach includes a set of activities which lead and

control the overall design, implementation and integration of the complex set

of interacting components.

In order to govern the complexity introduced from nonlinearities,

uncertainties and interactions, structural system decomposition, represented

by the design activities related with the classification and the identification of

the structural system components, and by the hierarchies (and the

interactions) between these components.

The decomposition is carried out focusing the attention on different

levels of detail: starting from a macro-level vision and moving towards

micro-level details.

We can decompose the structure as follows [Ref]:

Macro-scopic: related to geometric dimensions comparable with the

whole construction or parts with a principal role in the structural behavior;



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the parts so considered are called macro components which can be divided

into:

- The main structure, that has the objective to carry the main loads;

- the secondary structure, connected with the structural part directly

loaded by the energy production system;

- The auxiliary structure, related to specific operations that the turbine may

normally or exceptionally face during its design life: serviceability,

maintainability and emergency.

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Focusing the attention on the main structure, it consists in all the elements

that from offshore wind turbine. In general, the following segments can be

identified:

A. Support structure (the main subject of this study);

B. Rotor-nacelle assembly (RNA).

Mesoscopic (meso-level), related to geometric dimensions still relevant

if compared to the whole construction but connected with specialized role in

the macro components; the parts so considered are called meso-components.

In particular the support structure can be decomposed in the following parts:

A. Foundation: the part which transfers the loads acting on the

structure into the seabed;B. Substructure: the part which extends upwards from the seabed and

connects the foundation to the tower;

C. Tower: the part which connects the substructure to the

rotor-nacelle assembly.

Microscopic (micro-level), related to smaller geometric dimensions and

specialized structural role: these are simply components or elements.

II. An Introduction to OWT Foundations

i. Gravity based foundation[Ref]

Gravity foundations are concrete structures that use their weight to

resist wind and wave loading. Gravity foundations require unique fabrication

facilities capable of accommodating their weight (either drydocks, reinforced

quays, or dedicated barges).

They are less expensive to build than monopiles, but the installation



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costs are higher, largely due to the need for dredging and subsurface

preparation and the use of specialized heavy-lift vessels.

Also, they are most likely to be used where piles cannot be driven and the

region has dry-dock facilities for concrete construction.

Figure []: Gravity foundation

In Europe, gravity foundations will likely continue to fill an important

niche for shallow to moderate water depth regions where drivability is a

concern.

The structure requires a flat base and for most locations will require

some form for scour protection which is determined during detailed design

stage.

In general, gravity foundations are designed with the objective of

avoiding tensile loads (lifting) between the bottom of the support structure

and the seabed. This is achieved by providing sufficient dead loads such that

the structure maintains its stability in all environmental conditions solely by

means of its own gravity.

Gravity foundations are usually competitive when the environmental



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loads are relatively modest and the “natural” dead load is significant or when

additional ballast can relatively easily be provided at a modest cost.

Some of the wind farms where this type of foundation has been installed

are Rødsand 2 (Denmark); Vindeby(Denmark-first offshore wind farm in the

world); Kårehamn (Sweden), currently completing construction;

Middelgrunden, Nysted, Thornton Bank, and Lillgrund.

ii. Monopile Foundation[Ref]

Figure []: Monopile foundation

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Figure []: Monopile foundation

Monopiles are large diameter, thick walled, steel tubulars that are driven (hammered) or drilled (or both) into the seabed. Outer diameters usually

range from 4 to 6 m and typically 40–50% of the pile is inserted into the

seabed. The thickness and the depth the piling is driven depend on the design

load, soil conditions, water depth, environmental conditions, and design codes.

Pile driving is more efficient and less expensive than drilling.

The monopile support structure is a relatively simple design by which

the tower is supported by the monopile, either directly or through a transition

piece. The monopile continues down into the seabed. The structure is made of

a cylindrical steel tube.

The pile penetration depth is adjustable to suit the actual environmental

and seabed conditions. A limiting condition of this type of support structure is

the overall deflection (lateral movement along the monopile) and vibration,

and are subjected to large cyclic, lateral loads and bending moments (due to

the current and wave loads) in addition to axial loads (e.g. vertical loads due to

the transition piece).



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Monopiles are currently the most commonly used foundation in the

offshore wind market due to their ease of installation in shallow to medium

water depths. This type of structure is well suited for sites with water depth

ranging from 0-30m, but because they are limited by depth and subsurface

conditions, they are likely to decline in popularity in deeper water.

However, in nascent markets such as the U.S., and for the near term

future, monopiles are expected to be heavily employed.

Monopile variations are drilled monopile and drilled concrete monopile.

Grouting issues.The examples of wind farm using monopile foundation and

support structure are Horns Rev , Robin Rigg, Rhyl Flats.

iii. Tripods Foundation [Ref]

The tripod structure is considered to be a relatively lightweight three-legged

steel jacket compared to a standard lattice structure. Under the steel central

column, which is below the turbine, there is a steel frame which transfers the forces

from the tower into the three steel piles. Piles are installed at each leg position to

anchor the tripod to the seabed. The three piles are driven 10-20m into the seabed.

The tripod can also be installed using suction buckets.

The tripod foundation has good stability and overall stiffness. However it's not

suitable at water depths less than 6-7m, as this causes problems to the vessels

approaching the foundation as sufficient draught is need to clear the steel frame.



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Figure []: Tripods strucutre

The foundation is anchored into the seabed using a relatively small steel pile

(typically 0.9m diameter) on each corner.

Proponents state the advantages of the tripod are the suitability for greater water

depths, and a minimum of preparations required at the site before installation

(assuming absence of large boulders etc.). Erosion is not normally a problem associated

with this type of foundation. They go on to cite the foundations potential to save costs

compared to a more complex jacket design. The effect of scour can be less significant

when compared to the monopile support structure.

Others argue that tripods are not suited for locations with uneven sea beds with

large boulders, and that the complex main joint has a potentially greater risk of fatigue

from the large impact of wind and waves.

The tripod support structure is pre-assembled in an onshore construction yard.

The entire structure is placed on a suitable vessel such as a barge and transported to the

offshore location where it is slowly lowered onto the seabed ensuring that the structure



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is entirely level. Mud mats may be used at the three corners of the tripod ensure that the

structure settles onto the seabed in a stable manner, while providing support until the

foundation piles are in place. The foundation pin piles are each driven through pile

sleeves at the three corners at the bottom of the structure using a submersible hammer.

When the piles are at the required depth, a connection between the top of the pile and

the pile sleeve is made by filling the annulus with grout or by means of a swaged

connection.

Scour protection can be reduced if the foundation piles of a tripod support

structure are loaded mainly in the axial direction. No separate transition piece is

required, as the requirements for pile driving do not apply to the tripod and the

appurtenances can be connected directly to the tripod support structure.

The tripod foundation draws on the experiences gained in the oil and gas industry

where light weight three-legged steel jackets have been used for marginal offshore fields

Until now, the tripod foundation has been only used at Alpha Ventus, Borkum

Phase 1 (under construction), Global Tech I (under construction) but will also be used

at MEG Offshore I and Borkum Phase 2 offshore wind farms.

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Figure []: Tripods foundation construction

iv. Jacket(Braced-Frame) Foundation [Ref]

Jacket foundations are an open lattice steel truss template consisting of a

welded frame of tubular members extending from the mudline to above the

water surface Piling2 is driven through each leg of the jacket and into the

seabed or through skirt piles at the bottom of the foundation to secure the

structure against lateral forces. Jackets are robust and heavy structures and

require expensive equipment to transport and lift.



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Figure []: Jacket foundation

To date, jacket foundations have not been used extensively due to the

preference for shallow, near-shore environments. At around 50 m, jacket

structures are required. Jackets have been used for two of the deepest

developments, Beatrice (45 m) and Alpha Ventus (30 m), supporting large 5

MW turbines. Jackets are also commonly used to support offshore substations

Jackets can be used in deep water (100s of meters), although economic

considerations are likely to limit their deployment to water under 100 m.

Examples using jacket foundations and support structures are South Korean

offshore wind farm Tamra with water depth 3.5m and Beatrice Demonstration

project with water depth 45m in UK.

There are many variants of the three or four-legged jacket/lattice structure

typically consisting of corner piles interconnected with bracings with diameters up to

2m. The soil piles are driven inside the pile sleeves to the required depth to gain

adequate stability for the structure. The tubular joints are welded.

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These types of structures are considered well suited for sites with water depth ranging

from 20-50m according to the DNV. The minimum is 3.5m at the South Korean offshore

wind farm Tamraand the maximum depth for an operational project is 45m on

theBeatrice Demonstration project. Other projects in the plannng pipeline are

suggestion using jackets in water dephs up to 60-70m but these have yet to be

consented.

The transition piece forms the connection between the main jacket and the tower

of the wind turbine. Loads are transferred through the members mainly in axial

direction. The large base of the jacket structure offers large resistance to overturning.

The secondary steel includes the work platform, ladders and stairs, access systems,

J-tube, cables, and corrosion protection systems.

Proponents cite the advantages of the jacket structures as:

• Low wave loads in comparison to monopiles (the jacket structure is very stiff and

the area facing the wave movement is smaller than monopiles)

• Fabrication expertise is widely available, in part due to Offshore Oil and Gas

industry supply chain

Others cite disadvantages as:

• High initial construction costs and potentially higher maintenance costs

• Transportation is moderately difficult and expensive

v. Foundation Comparisons [Ref]

Comparisons Characteristics Advantages Disadvantages

Gravity

Mono-pile

Tripod

Jacket







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3. OWT Dynamics

I. Load Concept

i. Internal

Figure []: Rotor-Nacelle-Assembly (RNA)

The RNA system of an OWT plays an important role during operation.

Therefore, lots of literatures have investigated the control mechanisms when

generating electricity. However, from the view of structure mechanics, the

investigation of vibrations caused by rotor imbalances is essential and should

get the attention [11].

The growing size of new wind turbines leads to a more flexible structure

and therefore even bigger vibration amplitudes. Additionally, the operation of

large off-shore wind parks requires a careful remote monitoring of

imbalances. A well balanced rotor will prevent early fatigue and ensure a safe

and economic operation of the wind turbine. Imbalances affect the drive train

components as well as the structural health of the turbine [10]. Hence the

detection and elimination of imbalances are of vital importance.



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ii. External

Figure []: Loads from the interactions between an OWT and the environment

This is the whole view of an OWT. From the figure, its components and

assembly could be observed, such as blades, rotor, tower, support structure and

foundation. The blue color indicates sea level, and brown color represents sea bed.

II. Loads

i. Harmonic loading

1. Gravity loads on blades

2. Mass imbalance rotor

3. Aerodynamics imbalance rotor

4. Small regular waves

ii. Non-harmonic periodic loading

1. Wind-shear



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2. Yaw misalignment

3. Tower shadow

4. Rotational sampling of turbulence

iii. Non-periodic random loading

1. Seismic

2. Turbulence (small scale)

3. Random waves

III. Dynamics

i. Basic excitation behavior (The Concept of Resonance)

The importance of proper modeling of the structural dynamics can be

most illustrated by single degree of freedom mass-spring-damping system as

shown in Figure 7 [4].

Here is the equation of motion in 1DOF

mx(t) ̈ + cx(t) ̇ + kx(t) = F(t)

Figure []: Single degree of freedom mass-spring-damper system

After careful derivation of the motion equations, three steady state response

regions can be illustrated: (a) Quasic-static (b) Resonance (c) Inertia dominated

Figure []: a) Quasic-static b) Resonance c) Inertia dominated



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The dynamic amplification factor (DAF) depicts the ratio between the dynamic

response magnitude and the static response magnitude due to the same magnitude

of loading.

Figure []: DAF and phase lag diagram

The important conclusion that can be drawn from this review is that the

response of a wind turbine system subjected to time-varying loads needs to be

carefully assessed. Resonance should be avoided.

i. RNA Mass Imbalance & Rotational Sampling

To translate the basic model to a wind turbine system, the excitation

frequencies are examined first. The most visible source of excitation in a wind

turbine system is the rotor.

While the excitation with the rotor frequency (1P) is mainly fed by mass

imbalance, the higher harmonics are generated by atmospheric turbulence

(so-called ”rotation sampling”) [Ref].

These two frequencies are plotted in a graph as shown in Figure 8. The

horizontal axis represents the frequency [Hz] and the vertical axis represents

an arbitrary response without values. Though higher order excitations do

occur, here only 1P and 3P are considered as these are the primary excitations.

To avoid resonance, the structure should be designed such that its first



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natural frequency does not coincide with either 1P or 3P excitation. This

leaves three possible intervals.

A very stiff structure, with its first natural frequency above 3P is called a

stiff-stiff (structure-foundation combination [Ref]) structure; if the first

natural frequency falls between 1P and 3P, the structure is said to be soft-stiff

while a very soft structure with its first natural frequency below 1P is called a

soft-soft structure.

Figure []: Soft to stiff frequency intervals of a three bladed, constant rotational speed turbine

Similarly, the frequency plot for a variable turbine system shows that

interval for a soft-stiff design is correspondingly narrower.

Figure []: Frequency intervals for a variable speed turbine system

ii. Simple OWT model

Moreover, the support structure could be modeled as follows:



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Figure []: Structural model of a flexible wind turbine system

The natural frequencies of the sample model with a uniform beam at a

fixed base and a top mass could be estimated: [6].

One can derive the frequency equation by assuming shape function:

∅(x) = 1 − cos π2, and using Lagrangian formulation to get the generalized

mass and generalized stiffness to the derive the following frequency equation:

m∗ = ∫ μ[∅(x)2]dx + mp∅(L)

k∗ = ∫ EI[∅′′(x)2]dx

m∗q(t) ̈ + k∗q(t) = 0

Where,q(t) is the top displacement.

Where [6],



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Where,

The natural frequency of an OWT should be positioned on the frequency spectrum

to avoid resonance.

iii. Wave excitation and loads

For offshore wind turbine systems an additional source of excitation is

present in the waves. Wave frequencies are generally lower than the rotational

frequency of the rotor. Because waves come in various periods, they span a

wide range in the frequency band.

Figure 11: Occurrence of wave frequencies with plotted 1P and 3P frequencies.

Additionally, the wave loads on vertical towers are demonstrated. The

wave particle kinematics can now be used to calculate the loads on a structure

with the Morison Equation. The relative velocity of the structure can also be

incorporated but is ignored here as its magnitude is very small compared to

the water particle velocities. The Morison equation is an empirical formula to

calculate the hydrodynamic loads on slender members per unit length:



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Where,

In most situations, the inertial term could dominate the wave loads [4].

iv. Seismic effects

Wind turbines are already playing a critical role in the infrastructure of

many countries and regions. By recognizing the fact that a wind farm is a

collection of large, expensive, unique and homogeneous structures importantto the infrastructure, it becomes imperative that the probability of total

shut-down should be at a minimum. In the extreme event of a larger

earthquake in a city the spread of different building will equally allocate the

damage throughout the city.

Usually, the seismic design is based on earthquake spectrum. For

example:



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Figure []: Displacement response spectra of EI-Centro, 1940 earthquake ground motion

Figure []: Velocity response spectra of EI-Centro, 1940 earthquake ground motion



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Figure []: Accleration response spectra of EI-Centro, 1940 earthquake ground motion

However, at a wind farm, an earthquake can cause a collapse of every

turbine within a defined area. Consequently, some guidelines recommend

designing the wind turbines (or at least some of its components) as high

safety class [DNV, 2013; Risø, 2002; EC8-1, 2004] [12].

From the researches [12, 13], several results could be

observed:

1. Experimental contributions:

A. For small utility scale turbines, a first mode response was



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shown to provide a reasonable approximation. For larger

modern turbines, higher modes may play a prominent role in

the overall seismic response.

B. Experimental results on a 65-kW turbine show that

degradation of the connection between the tower and

foundation was identified as a possible and undesirable

damage mechanism.

C. Both first and second tower bending modes in the fore-aft and

side-to-side directions show little out of plane deformation,

supporting assumed independence between fore-aft and

side-to-side motions in multi-modal codes.

D. An increase in damping, likely due to aerodynamic interaction,

was identified while the 900-kW turbine was operating.

2. Numerical contributions:

A. The relatively stiff soil produced little SSI influence on the first

and second longitudinal modes. In contrast, when softer soils

were investigated, a more significant influence was apparent.

The second bending mode behavior was clearly impacted,

showing a reduction in frequency and increased foundation

rotation. B. For earthquake like motion, it was found that the soil stiffness

can influence the maximum moment and shear demand

distributions. Unlike the differences in natural frequencies, this

shift in demand parameter distribution may influence turbine

design. In particular, the increased demand at higher

elevations, near maximum displacement in the second mode,

may require special consideration of this portion of the tower

for large turbines installed in seismically active regions.

C. In contrast to the possibility of tower moment demand being

driven by seismic demand, results show that it is unlikely that

even strong shaking will result in design driving loads for the

turbine blades.

D. The dynamic wind-induced load mainly produced large

displacements – larger than most of the displacements from

earthquake. Also, the dynamic wind-induced load proved to

yield larger response than the statically applied wind. This

result shows the importance of either; 1) make sure to use



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sufficient conservative static load, or 2) apply turbulent

wind-induce load.

v. Aerodynamics effects

The aerodynamic loading is caused by the flow past the structure, in

other words the blades and the tower. The wind field seen by the rotor varies

in space and time due to atmospheric turbulence as sketched in Figure .

As also seen in Figure 13.4, the wind field is characterized by shear; in

other words the mean wind speed increases with the height above the ground.

For neutral stability this shear may be estimated as:

V 10min(x ) is the time averaged value for a period of 10 minutes at a height

x above the ground.

V 10min(h ) is the time averaged value at a fixed height h and zo is the

so-called roughness length.

vi. Foundation Modeling (Soil-Structure Interaction)

A. Transfer of horizontal loads, vertical loads and moments[Ref]

In the design of offshore support structures, two main directions of

load transfer must be analyzed.

First, the foundation must be able to transfer all vertical loads, the

weight of the structure, to the soil. This is mainly done by friction: the

soil around the pile takes a small load per area of surface and as long as

the load-transfer-area is large enough, the foundation will suffice. Next to

the friction on the outside of the pile, the steel rim of the pile and the soil



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plug inside the pile may also give vertical bearing capacity. For monopiles

of 4 m diameter and more, the extra pile plug resistance is usually not

taken into account due to the large diameter of the pile.

Second, for overturning moments, multi-legged structures mainly

rely on vertical capacity. Due to the fixation in the frame, the piles of a

multi-legged structure deform in an S-shape, deforming at the same time ,

subjected to horizontal soil resistance. The overturning moment is then

transferred as axial loads to opposing foundation piles as shown in

Figure 2.61.

For monopiles, all horizontal loads and moments must be

transferred directly to horizontal soil reactions, as shown in the

right-hand side of Figure 2.61. As the pile is not fixed at the top, it is free

to rotate and translate. For offshore wind turbines on monopiles, this

horizontal load transfer usually dictates the pile length: the pile must be

long enough to mobilize enough soil over its length to transfer all loads

and prevent "toe kick": displacement of the tip of the pile.

B. Soil Springs

To model the soil reaction loads a set of soil springs is used. Figure

2.62 shows the springs for the horizontal and vertical direction as well as

for the pile plug [57].



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All springs in Figure 2.62 are non-linear.

The properties can be derived from site measurements through

calculation methods prescribed in the standards [52], [77]. The typical shape

of these curves is shown in Figure 2.63. For the first part, left-hand side, the

soil reacts linearly and elastically; when the load is released, the soil will

return to its original state. Beyond a break point in the curve, deformations

will become permanent and the soil starts to lose resistance.

For extreme load cases and foundation design, the full non-linear model

must be used. For load calculations of the offshore wind turbine and its

support structure, a reduced model can also be used as described next.



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C. Stiffness Matrix model for foundation representation

The non-linear spring model can be created in a straightforward way in

a finite element program. For fatigue load simulations of the offshore wind

turbine however, the full complexity of the non-linear systems is usually not

required: most soil reactions remain within the linear elastic range. To reduce

calculation time, a stiffness matrix model can be used, which has shown

excellent agreement with full non-linear models [57]. The foundation

properties are represented by two coupled springs for lateral and rotational

reactions as shown in Figure 2.64.

The spring properties are derived by applying two load sets that aretypical for operational conditions of the offshore wind turbine to the

non-linear model and using the outcome to derive the spring constants in:

Although other models exist, the non-linear p-y model for foundation

detailing and the coupled spring model for offshore wind turbine load cases

were proven to be the most suitable for offshore wind turbine design. For

more details on these and other models and comparison with measurements

on offshore wind turbines, the reader is referred to [57] [58].



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vii. Suitable Stiffness of An OWT System

Due to the rotation of the rotor, the dynamic loads on the wind turbine

are lumped close to discrete frequencies i.e. the rotor frequency and the lower

blade multiples. In case of the soft-soft or soft-stiff design, the strong blade

excitation (3P) is beyond the first eigen-value of the support structure and has

therefore in general a lower dynamic amplification factor (DAF) than a

stiff-stiff design. [5]

Figure[]: Dynamic amplification factor of the tower top loads for three OWT designs.(2% structural damping, 3% aerodynamic damping)

Stiffness has been identified as one major aspect in the design of OWT support

structures which has a strong influence on technical and economic performance.

Structural dynamics should be considered, at least in a qualitative manner, at an

early design stage. Optimum OWT design should be based on an integrated design

approach and be related directly to the particular site conditions and the chosen

concepts for wind turbines and support structures.

As far as structural dynamics are concerned, structures with an overall stiff

behavior e.g. stiff-stiff characteristics are problematic due to the increase of wind

induced fatigue. So, at least in the upper part flexibility should be introduced.

In contrast, soft-stiff support structures should be possible for most sites but

not for all generic concepts. Problems may occur if the design range for the

fundamental eigen-frequency is not large enough.

Soft-soft designs are economically interesting but inherently prone to wave

fatigue thus very careful design is required. [5]

A stiff-soft system is not recommended for the capacity of a soft foundation



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would compromise the whole structure stability when the support structure is

stiff.

4. Design Tools for OWT Modeling

I. FAST( with BModes)

i. Fatigue, Aerodynamics, Structures, and Turbulence

1. Sample input

A. Geometry

i. Tower: Onshore / 20 nodes / 87.6m

ii. Blade length: 63 m

iii. Rotating frequency: 12.1 rpmB. Loads

i. Aero dynamics / Gravity / Seismic

ii. Simulation of seismic loads using the FAST

iii. Movable platform – A force and moment applied to

the tower base platform, without rocking and SSI

effects.

2.

Sample outputA. Tons of parameters, primarily including displacements,

velocities, accelerations corresponding to time steps.

Figure []: Modes of operation



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Figure []: Input and output files

ii. BModes

1. Pre-processor for FAST

A. B(eam)Modes for blade or tower modal analysis.

B. FAST uses uncoupled modes for fore and lateral motion of

the tower and ignores the torsion DOF.

C. The BModes-computed scheme of coupled-modes

overcomes this problem.

Figure []: BModes element model



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II. SAP2000

i. SAP2000 is common used in civil engineering industry. However, it is

not an aerodynamic software. The wind (when of interests) is applied as

an equivalent an equivalent thrust-force working on the rotor with a load

value depending on the wind speed.

Figure []: Wind turbine model in SAP2000

III. Bladed [Ref]

i. Bladed is the industry standard integrated software package for the

design and certification of onshore and offshore turbines. It provides

users with a design tool that has been extensively validated against

measured data from a wide range of turbines and enables them to

conduct the full range of performance and loading calculations.

ii. It offers

1. Multibody structural dynamics

2. Rotor

3. Drive train

4. Generator and electrical

5. Control

6. Tower and nacelle



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7. Wind field model

8. Waves and currents

9. Response Calculations

10. Post-processing facility

11. Graphics

12. Project management

13. Seismic design

14. Offshore support structure design

Figure []: Bladed snapshot

Figure []:Bladed snapshot

5. Present Wind Turbine Health Monitoring Techniques

6. References



35

1. References

1. http://www.smh.com.au/business/carbon-economy/asia-to-lead-quadrupli

ng-of-wind-energy-by-2030-siemens-20130827-2smsb.html

2. http://web3.moeaboe.gov.tw/ECW_WEBPAGE/webpage/book_en1/page1.

htm

3. Supporting the winds of change

4. Structural Design and Analysis of Offshore Wind Turbines from a

System Point of View

3. Design of Offshore Wind Farms. LIC Engineering.

4. Design pf Support Structures for Offshore Wind Turbines. Proefschrift

5. Soft to stiff: A fundamental question for designers of offshore wind energy

converters.

6. Wind turbine structural dynamics - A Review of the principles for Modern

Power Generation, Onshore and Offshore.

7. Malhotra, S. Design & Construction Consideration for Offshore Wind Turbine

Foundations in North America.

8.

http://sbwi.dhigroup.com/end_user_workshop/02_Design%20of%20Offshore%

20Wind%20Farms.pdf

9. Bontempi, F., Basis of Design and expected Performances for the Messina Strait

Bridge, Proceedings of the International Conference on Bridge Engineering –

Challenges in the 21st Century, Hong Kong, 1-3 November, 2006.

10. Ciang, C.C.; Lee, J.; Bang, H. Structural health monitoring for a wind turbine

system: A review of damage detection methods. Meas. Sci. Technol. 2008, 19,

122001.

11. Mass and Aerodynamic Imbalance Estimates ofWind Turbines - Jenny

Niebsch 1,?, Ronny Ramlau 2 and Thien T. Nguyen 3

12. Seismic Response of Wind Turbines

http://www.smh.com.au/business/carbon-economy/asia-to-lead-quadrupling-of-wind-energy-by-2030-siemens-20130827-2smsb.html





http://web3.moeaboe.gov.tw/ECW_WEBPAGE/webpage/book_en1/page1.htm











13. An experimental and numerical study of wind turbine seismic behavior

An Overview of Support Structure and Foundation System of Wind Turbines 20131120

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