Reinforced Hybrid Stay Cable Pipe With Lower Thermal Expansion

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Solution Overview

Problem

Conventional stay cables face limitations in buckling resistance, tensile strength, and thermal expansion, leading to increased weight, cost, and installation challenges, especially in long or high-span structures, due to the material properties of traditional pipes and the need for expansion sleeves.

Innovation Solution

A hybrid pipe with reinforcing elements, such as metal plates and curved profiles, integrated into the pipe structure to enhance mechanical properties and reduce thermal expansion, allowing for increased buckling resistance and tensile strength while eliminating the need for expansion sleeves and reducing weight and installation complexity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If conventional steel pipes are used for stay cables, then tensile strength is sufficient, but weight increases and corrosion protection cost increases

Engineering Contradiction:
Improvetensile strengthVSAvoidpipe weight
Core Design Contradiction:
StrengthVSWeight of moving object

Solution Approach 1:

The patent employs a composite structure combining steel strands (for tensile strength) with a polyethylene pipe (for corrosion protection and reduced weight). This hybrid composite material approach allows the stay cable to achieve the required mechanical properties while reducing overall weight and eliminating the need for additional corrosion protection systems.

Inventive Principle:
Principle #40Composite materials

2Weight of moving object

If plastic pipes (PE/HDPE) are used for stay cables, then weight is reduced and corrosion protection is provided, but buckling resistance decreases

Engineering Contradiction:
Improvepipe weightVSAvoidbuckling resistance
Core Design Contradiction:
Weight of moving objectVSStrength

Solution Approach 1:

The patent creates a composite system where steel strands are placed inside a polyethylene pipe. The steel strands provide the necessary compressive strength and buckling resistance, while the polyethylene pipe provides corrosion protection and reduces overall weight. This composite material strategy resolves the contradiction between weight reduction and buckling resistance.

Inventive Principle:
Principle #40Composite materials

3Stability of the object's composition

If expansion sleeves are added to compensate thermal expansion, then thermal dilatation is controlled, but device complexity and installation difficulty increase

Engineering Contradiction:
Improvethermal expansion controlVSAvoidinstallation complexity
Core Design Contradiction:
Stability of the object's compositionVSDevice complexity

Solution Approach 1:

The patent selects polyethylene as the pipe material specifically for its coefficient of thermal expansion that matches or is compatible with steel strands. By changing the material parameter (selecting PE with appropriate thermal properties), the patent eliminates thermal expansion incompatibility issues, thereby avoiding the need for expansion sleeves and reducing installation complexity.

Inventive Principle:
Principle #35Parameter changes

4Strength

If pipe thickness is increased to prevent buckling, then buckling resistance improves, but weight and installation difficulty increase

Engineering Contradiction:
Improvebuckling resistanceVSAvoidpipe weight
Core Design Contradiction:
StrengthVSWeight of moving object

Solution Approach 1:

Instead of increasing polyethylene pipe thickness to improve buckling resistance (which would increase weight), the patent uses a composite approach where steel strands provide the compressive strength and buckling resistance. This allows the use of thinner, lighter polyethylene pipe while maintaining adequate buckling resistance through the steel component.

Inventive Principle:
Principle #40Composite materials

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 hybrid pipe provides improved mechanical properties, reduced thermal dilatation, and self-supporting capabilities, enabling the installation of longer stay cables with reduced weight and cost, and improved aerodynamic performance.

Implementation Method 1

A hybrid pipe with reinforcing elements, such as metal plates and curved profiles, integrated into the pipe structure to enhance mechanical properties

Methodology Applied
Scientific EffectComposite materials: Composite Materials

Implementation Method 2

reduced thermal dilatation

Methodology Applied
Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentEP3568526B1Hybrid pipe for stay cable and its manufacturing method
Publication Date: 2023.10.25 VSL INT AG
  • EP3568526B1 patent drawingFigure 1a~2
  • EP3568526B1 patent drawingFigure 3a~3c
  • EP3568526B1 patent drawingFigure 3d~3f

AI summary

The present invention relates to a hybrid pipe (1) for stay cable, comprising a tubular shaped wall (15), the wall having an internal face (18) and an external face (19). The hybrid pipe (1) further comprises at least one reinforcing element (12, 22), the reinforcing element (12, 22) being provided at the wall (15) to form the hybrid pipe (1) such that the hybrid pipe (1) has a higher mechanical properties/ resistance such as higher buckling resistance, higher tensile strength and/or a lower thermal dilatation than the wall (15) itself. The present invention also relates to a cable-stayed system comprising such a hybrid pipe (1) and a method of manufacturing such a hybrid pipe (1).