Cable Strake Design for Rain-Wind Vibration Mitigation
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Solution Overview
Problem
Cables supporting structures like bridges and antennas experience undesirable vibrations due to wind and rain, which existing viscous or frictional dampers fail to fully mitigate, as they do not prevent rain-wind induced rivulets that alter the aerodynamic profile and exacerbate vibrations.
Innovation Solution
A tension element with a cable and strakes, where the strake height is less than 5% of the cable diameter, featuring a concave surface portion facing away from the cable to deflect water and reduce rivulet formation, thereby minimizing rain and wind-induced vibrations without increasing drag.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If viscous or frictional dampers are introduced to bridge cables, then vibrations are reduced, but rain-wind induced rivulets are not prevented and aerodynamic profile is altered
Solution Approach 1:
The cable surface is segmented into multiple longitudinal strakes that divide the water flow path. This segmentation prevents the formation of continuous rivulets by breaking up water accumulation into smaller segments that can be more effectively managed and directed away from the cable surface.
Solution Approach 2:
The strakes act as intermediary elements between the rain-wind flow and the cable surface. These protrusions intercept water droplets and redirect them before they can form harmful rivulets on the cable, serving as a mediating structure that protects the aerodynamic profile.
2Object-affected harmful factors
If strakes are added to reduce vibrations, then aerodynamic properties improve, but drag force may increase
Solution Approach 1:
The strakes are designed with specific local characteristics: height between 0.5-5% of cable diameter, longitudinal extent of 10-50% of cable circumference, and specific spacing patterns. These localized geometric properties are optimized to provide vibration reduction while minimizing interference with overall aerodynamic flow and drag.
Solution Approach 2:
The invention optimizes multiple geometric parameters of the strakes including height (0.5-5% of cable diameter), length (10-50% of cable circumference), spacing (20-100mm), and cross-sectional shape. By carefully controlling these parameters, the system achieves vibration reduction while maintaining acceptable drag characteristics.
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 solution effectively prevents rain rivulet formation and minimizes wind-induced vibrations, improving the aerodynamic properties of the cable without increasing drag, thus addressing the limitations of existing damping methods.
Implementation Method 1
the first strake surface portion being concave, and wherein the first strake surface portion extends from the strake root part to the strake end part to provide a ramp for rivulets flowing longitudinally along the outer surface of the cable
Data Source
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AI summary
The invention provides a construction comprising a structural element and at least one cable (101) arranged in tension to carry at least a part of the weight of the structural element. The cable defines an outer surface (102) onto which at least one strake (104) forms a protrusion for reducing rain and wind induced vibrations. The strake has a height being a distance from a strake root part connected to the outer surface of the cable and a strake end part terminating the strake outwards away from the cable, and the strake has a width being transverse to the height, the width decreasing in the direction from the strake root part towards the strake end part. The height is less than 5 percent of the diameter of the cable. Furthermore, the strake comprises a first strake surface portion facing away from the cable, which first strake surface portion is concave or straight.