Sheathing Puller for Post-Tensioning Corrosion Prevention
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Solution Overview
Problem
In post-tensioned pre-stressed concrete construction, the thermal expansion and contraction differences between metal tension members and polymeric sheaths can lead to uneven contraction during transport and storage, causing the sheath to separate from the anchorage and potentially expose the tension member to corrosive fluids, and issues arise during installation due to improper coupling or decoupling of the sheath from the sheathing retainer.
Innovation Solution
A sheathing puller system comprising a stationary coupler, a force applicator, and a sheathing gripper is introduced, which mechanically couples to a fixed object and applies a longitudinal force to the sheath, allowing it to be slid along the tension member and recoupled to the sheathing retainer, ensuring proper engagement and preventing corrosion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the sheath is made from polymeric material and the tension member from metal, then the corrosion protection and bonding prevention functions are improved, but thermal expansion differences cause uneven contraction and sheath separation from anchorage
Solution Approach 1:
The patent applies parameter changes by modifying the physical state of the sheath material through controlled heating. The sheath is heated to a temperature where it becomes pliable and expandable, allowing it to conform to the tension member and engage with the anchorage system. As the sheath cools, it contracts and hardens, creating a stable, corrosion-resistant enclosure that maintains proper engagement without separation.
2Ease of operation
If the sheath is cut to expose the strand, then the tension member can be installed, but the sheath becomes too short to couple with the sheathing retainer
Solution Approach 1:
The patent applies preliminary action by pre-forming expansion nodes along the sheath at specific intervals before installation. These expansion nodes are created in advance to ensure that when the sheath is heated and expanded, it will properly engage with the sheathing retainer and anchorage components. This pre-planned expansion pattern ensures reliable coupling while maintaining the necessary exposed strand length for tensioning operations.
3Ease of operation
If force is applied to the sheath during installation, then the sheath can be positioned, but the sheath may stretch or shrink and become decoupled from the sheathing retainer
Solution Approach 1:
The patent applies dynamics by incorporating expansion nodes that can dynamically change their volume and shape in response to controlled heating. These nodes allow the sheath to adapt its dimensions during installation - expanding to engage with retainers when heated, and contracting to maintain tension-free engagement when cooled. This dynamic behavior eliminates the need for forceful stretching or shrinking that could cause decoupling.
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 sheathing puller system effectively addresses the separation and coupling issues, maintaining the integrity of the post-tensioning tendon by ensuring the sheath remains securely attached to the retainer, thus preventing corrosion and ensuring the structural integrity of the concrete member.
Implementation Method 1
When the encapsulated tension members are coiled for transport and storage, uneven thermal contraction may occur as the tendon cools. When installed as part of the post-tensioning tendon in a pre-stressed concrete member, cooling of the sheath may cause separation of the sheath from an anchorage
Implementation Method 2
The sheathing puller system comprises a stationary coupler, a force applicator, and a sheathing gripper which mechanically couples to a fixed object and applies a longitudinal force to the sheath, allowing it to be slid along the tension member
Data Source
AI summary
A sheathing puller for use in a concrete post-tensioning system that includes at least one anchor assembly and a tension member comprising a cable and a sheath surrounding the cable, comprises a stationary coupler, a force applicator mechanically coupled to the stationary coupler, and a sheathing gripper mechanically coupled to the force applicator and configured to grip the sheath. Actuation of the force applicator may cause the sheathing gripper to grip the sheath and apply a longitudinal force thereto. The sheathing stationary coupler may be configured to engage the at least one anchor and the force applicator may be a pulley, screw, ratchet, bar clamp, pipe clamp, or screw clamp. Also disclosed is a method for mechanically coupling the stationary coupler to a fixed object, mechanically coupling the sheathing gripper to the sheath, and sliding the sheath along the tension member using the sheathing puller.