Bolt Connection for Wind Tower Lattice Pretension
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Solution Overview
Problem
Conventional bolt connections in lattice wind turbine towers face issues with limited pretension length due to interference fits, leading to potential early failure and loosening, especially under wind-induced vibrations, and existing arc welded joints have drawbacks.
Innovation Solution
The bolt connection design features a pin component with a textured shaft and internal threaded bore, providing a sufficient exposed bolt length for pretension deformation by ensuring the pin component's shaft extends into structural components with a tight friction fit, while the bolt component's threaded shaft engages within the pin's bore, increasing the free length for pretension distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the bolt uses a long interference fit between chamfered shaft section and through holes to provide strength, then connection strength is improved, but the pretension length available on the shaft is reduced
Solution Approach 1:
The bolt is divided into two separate components: a pin component with the interference fit function and a bolt component with the pretension function. The pin component shaft provides the friction fit connection while the bolt component threaded shaft provides the pretension, eliminating the conflict between these two functions in a single bolt design.
Solution Approach 2:
The bolt component is nested within the pin component, where the bolt component threaded shaft engages within the threaded internal bore of the pin component. This nesting allows both components to work together while maintaining their respective functions independently.
2Length of moving object
If the bolt uses a short interference fit to provide more pretension length, then pretension capability is improved, but connection strength is reduced
Solution Approach 1:
By separating the interference fit function (pin component) from the pretension function (bolt component), the design can optimize each function independently. The pin component shaft can have sufficient length for strong friction fit while the bolt component can have sufficient length for proper pretension.
3Reliability
If arc welded joints are used instead of bolted connections to prevent loosening, then connection reliability is improved, but manufacturing complexity and potential defects increase
Solution Approach 1:
The pin component shaft is designed with a textured outer circumferential surface that creates a tight friction fit in advance, providing preliminary stabilization against loosening before the bolt component is fully tightened. This preliminary friction fit complements the pretension action of the bolt component.
Solution Approach 2:
The textured outer circumferential surface on the pin component shaft changes the friction parameter, creating increased resistance to loosening through the friction fit mechanism, providing an alternative to welding for preventing connection failure.
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
This configuration enhances the balance between strength and maintenance by providing increased pretension length, reducing the risk of bolt-nut loosening and improving the durability of the connection under operational conditions.
Implementation Method 1
The shaft (66) has a diameter such that the textured outer circumferential surface (68) forms a relatively tight friction fit within the aligned bores (74) of the structural components (76, 78) and prevents relative rotation of the pin component (62) within the bores (74)
Implementation Method 2
The threaded shaft (82) engages within the threaded internal bore (70) of the pin component (62)... the threaded shaft (82) has a significantly increased free length section (28) as compared to the prior art configuration... providing for an enhanced and increased distribution of the required specified pretension placed on the bolt component (80)
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
A bolt connection assembly (60) is provided that is particularly suited for connecting components of a lattice structure wind tower (48). The assembly includes a pin component (62) having a head (64) and a shaft (66), with the shaft having a textured friction-fit outer circumferential surface (68). The shaft further includes a threaded internal bore (70). A bolt component (80) having a threaded shaft (82) engages within the threaded internal bore. In an assembled state of the pin component and bolt component, the threaded shaft has a free length section that extends into the threaded internal bore for increased distribution of a specified pretension of the bolt component.