Pocket Cap for Post-Tensioned Concrete Strand
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Solution Overview
Problem
In post-tensioned concrete construction, existing anchor systems face challenges in preventing corrosion and concrete bonding, which can lead to structural integrity issues and increased maintenance costs due to fluid ingress and restricted movement of post-tensioning tendons.
Innovation Solution
A system comprising an anchor body, a strand with a pocket cap, and a pocket former that forms a cavity in the concrete to encase the tendon, preventing fluid intrusion and allowing for easy access and tensioning, while using a grease-filled sheath to protect the metal strand from corrosion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the strand is exposed at the end of the concrete member, then access for tensioning is improved, but fluid ingress and corrosion risk increase
Solution Approach 1:
A pocket cap is introduced as an intermediary component between the exposed strand end and the environment. The pocket cap covers the strand end while including an opening that allows access for tensioning operations, simultaneously preventing fluid ingress and corrosion to the strand.
2Object-affected harmful factors
If the sheath is made more restrictive to prevent corrosion, then protection is improved, but movement of the post-tensioning tendon is restricted
Solution Approach 1:
The sheath is designed with differential properties: it is restrictive and protective in most areas to prevent corrosion, but includes a localized movable portion that allows tendon movement where needed. This local variation in quality resolves the contradiction between protection and mobility.
3Ease of repair
If a pocket former is used to create a cavity, then access and maintenance are improved, but device complexity increases
Solution Approach 1:
A pocket former is used during the concrete pouring process to preliminarily create a cavity in the concrete member. This cavity is formed in advance to provide access for future tensioning and maintenance operations, eliminating the need for complex post-construction modifications.
Data Source
AI summary
A system for post tensioning a concrete member is disclosed. The system may include an anchor body, and a strand, the strand inserted through the anchor body. The strand may have a strand end and an outer diameter. The system may also include a pocket cap, the pocket cap positioned around the strand. The pocket cap may have a cylindrical interior wall, the cylindrical interior wall having a pocket cap diameter corresponding to the outer diameter of the strand.