Radially Adjustable Ring Stiffener for Wind Tower Buckling Resistance

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Solution Overview

Problem

Conventional wind turbine towers face challenges in balancing reduced material costs with structural strength, as thinner walls increase flexibility and susceptibility to buckling, while reinforcement methods like welding can compromise fatigue strength and are costly.

Innovation Solution

A radially adjustable ring stiffener is used to reinforce tubular structures by adjusting its radius to engage the inner surface through friction, without welding or fastenings, effectively increasing the cross-sectional thickness and buckling resistance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If the wall thickness of tower sections is reduced to minimize material cost, then material cost is reduced, but the strength and buckling resistance of the tower is reduced

Engineering Contradiction:

Improvematerial costVSAvoidbuckling resistance

Core Design Contradiction:

Quantity of substanceVSStrength

Solution Approach 1:

The tower is divided into multiple tower sections that can be individually manufactured and transported. Ring stiffeners are applied as separate segments at specific locations along the tower to reinforce buckling-resistant areas without requiring the entire tower to have increased wall thickness, thus maintaining cost efficiency while improving structural strength where needed.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Ring stiffeners are strategically positioned at specific locations along the tower where buckling resistance is most critical, such as at transitions between tower sections or at heights where mechanical loads are highest. This localized reinforcement approach provides enhanced strength precisely where required without unnecessarily increasing material costs across the entire tower structure.

Inventive Principle:

Principle #3Local quality

2Strength

If ring stiffeners are welded to the tower to reinforce vulnerable sections, then buckling resistance is improved, but fatigue strength is reduced due to hotspots from the welding process

Engineering Contradiction:

Improvebuckling resistanceVSAvoidfatigue strength

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

A friction-based coupling mechanism serves as an intermediary between the ring stiffener and the tower wall, replacing direct welding. The ring stiffener is expanded radially outward to create frictional contact with the tower's inner surface, providing reinforcement without the harmful thermal effects of welding that would compromise fatigue strength.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The welding process is replaced with a mechanical friction-based attachment system. The ring stiffener uses radial expansion to generate sufficient friction force to secure it to the tower structure, substituting the thermal-mechanical welding process with a purely mechanical attachment method that preserves the tower's fatigue properties.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Strength

If ring stiffeners are welded to reinforce the tower, then structural strength is improved, but the complexity and cost of installation increases

Engineering Contradiction:

Improvestructural strengthVSAvoidinstallation complexity

Core Design Contradiction:

StrengthVSEase of manufacture

Solution Approach 1:

The ring stiffener incorporates a dynamic expansion mechanism that allows it to be inserted in a compact state and then expanded radially outward to engage with the tower wall. This dynamic transformation simplifies the installation process compared to welding, as it requires only insertion and activation of the expansion mechanism rather than complex welding procedures.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The ring stiffener undergoes a parameter change in its radial dimension during installation. It is inserted with a smaller radius and then expanded to a larger radius to create frictional engagement with the tower wall. This parameter change enables a simpler, non-welding installation process while maintaining effective structural reinforcement.

Inventive Principle:

Principle #35Parameter changes

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The method enhances structural strength without reducing fatigue strength, allowing for economical reinforcement of existing towers and extending their lifespan.

Implementation Method 1

engage an inner surface of the tubular wind turbine structure with a radial force that holds the ring stiffener at the reinforcement position by means of friction between the ring stiffener and the tubular wind turbine structure

Methodology Applied

Scientific EffectFriction: Friction

Data Source

PatentUS12442207B2Reinforcement of wind turbine structures

Publication Date: 2025.10.14 VESTAS WIND SYSTEMS AS

AI summary

An aspect of the invention relates to a method of reinforcing a tubular wind turbine structure using a radially adjustable ring stiffener. The ring stiffener comprises a pair of adjacent ring segments coupled together by a coupling means configured to permit radial adjustment of the ring stiffener by varying an intersegmental separation between adjacent ends of those ring segments. The method comprises: positioning the ring stiffener at a reinforcement position within the tubular wind turbine structure; and adjusting the intersegmental separation between the pair of adjacent ring segments to increase the radius of the ring stiffener; and thereby to engage an inner surface of the tubular wind turbine structure with a radial force that holds the ring stiffener at the reinforcement position by means of friction between the ring stiffener and the tubular wind turbine structure.