Cold Heading Wedge for Post-Tensioning Concrete
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Solution Overview
Problem
Existing wedges for post-tensioned concrete anchors lack efficient methods for forming and enhancing the gripping force on tendons, particularly in post-tensioned pre-stressed concrete construction, where consistent engagement with tapered recesses is crucial for maintaining tensile stress reduction.
Innovation Solution
The method involves cold heading a wire to form wedge blanks, which are then refined and treated to create wedge-shaped components that securely engage with the tendon by moving into a tapered recess, utilizing a process that includes forming dies and potential additional treatments like tumbling or heat treatment to enhance the wedges' gripping capability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If traditional wedge forming methods are used, then manufacturing simplicity is maintained, but gripping force and engagement consistency deteriorate
Solution Approach 1:
The wire is cold-headed into a predetermined wedge blank shape with pre-formed geometry including the wedge angle and gripping surface contours before final assembly. This preliminary forming action ensures consistent dimensional accuracy and gripping characteristics while enabling automated high-volume production through die-based forming processes.
2Reliability
If wedge geometry is simplified for ease of manufacture, then production efficiency improves, but engagement reliability with tapered recess deteriorates
Solution Approach 1:
The wedge blank is cold-headed with precisely controlled geometric parameters including wedge angle, gripping surface area, and profile contours that are optimized for reliable engagement with the tapered recess. These parameters are maintained within tight tolerances through controlled cold heading processes that ensure consistent form and fit while enabling efficient automated manufacturing.
3Manufacturing precision
If cold heading process is implemented, then manufacturing precision and gripping capability improve, but process complexity and equipment requirements worsen
Solution Approach 1:
Traditional hot forging or machining processes are replaced with cold heading operations that use controlled mechanical compression and forming dies to shape the wire into wedge blanks. This substitution provides superior dimensional accuracy and surface integrity while enabling automated production, though it requires specialized cold heading equipment with precise die positioning and controlled force application.
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 approach results in wedges that provide a reliable and consistent gripping force on the tendon, effectively maintaining the pre-stressed state of the concrete by ensuring secure engagement within the anchor's tapered recess, thereby enhancing the structural integrity of post-tensioned concrete structures.
Implementation Method 1
cold heading a wire to form wedge blanks
Implementation Method 2
cold heading a wire to form wedge blanks
Implementation Method 3
wedges to further engage the strand
Data Source
Figure 1
Figure 2
Figure 3A~3D
AI summary
A wedge for use in post tensioning concrete is formed by cold heading. The cold heading operation may include providing a wire, feeding the end of the wire into a cold heading apparatus, cold heading the end of the wire to form at least one wedge blank, and finishing the wedge blank to form the wedge.