Collapsible Element Pocket Former for Post-Tensioned Concrete
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Solution Overview
Problem
In post-tensioned prestressed concrete construction, existing methods face challenges in creating a pocket for access to the stressing-end tendon after concrete hardening, as conventional pocket formers are difficult to remove and often result in incomplete or compromised protection against corrosion and fire.
Innovation Solution
A pocket former with a collapsible element extending radially outward from its body, which is inserted between the stressing-end anchor and the concrete form, allowing the tension member to be encased and the pocket former to be collapsed inward, forming a cavity upon removal, facilitating access and protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional pocket formers are used, then the pocket is formed to allow access to the tendon, but the pocket former is difficult to remove and may result in incomplete protection
Solution Approach 1:
The pocket former incorporates a collapsible element that transitions from a rigid extended state during concrete pouring to a collapsed state for easy removal. This dynamic transformation allows the pocket former to maintain its structural integrity during use while enabling simple extraction after hardening, resolving the contradiction between ease of removal and protection completeness.
Solution Approach 2:
The pocket former is divided into a body portion and a collapsible element that can be separated or collapsed independently. This segmentation allows the collapsible element to be compressed into the body for removal while the body remains intact to maintain the pocket structure, facilitating both easy removal and reliable protection.
2Ease of operation
If the pocket former is removed after concrete hardening, then access to the tendon is enabled, but the collapsible element must be compressed which requires significant force
Solution Approach 1:
The collapsible element is designed with dynamic collapse characteristics that allow it to buckle and compress progressively under applied force. This dynamic collapse mechanism reduces the peak force required compared to compressing a rigid structure, as the element can deform and fold rather than resist uniform compression throughout.
Solution Approach 2:
The collapsible element utilizes flexible material properties to enable easy compression and collapse. The flexible construction allows the element to bend, fold, and compress into the pocket former body with relatively low force, making removal practical while maintaining structural integrity during the concrete pouring process.
3Reliability
If the collapsible element extends radially outwardly, then it provides adequate spacing and protection, but it increases the overall size of the pocket former
Solution Approach 1:
The collapsible element transitions from an extended radial configuration during concrete pouring to a collapsed configuration during removal. This dynamic size change allows the element to provide adequate spacing and protection (when extended) while minimizing the overall footprint (when collapsed), resolving the contradiction between protection effectiveness and size.
Solution Approach 2:
The collapsible element is designed to nest within or alongside the pocket former body when collapsed. This nesting arrangement minimizes the overall size and space required for storage and removal, while the same element extends radially outward during the pouring process to provide the necessary spacing and protection, effectively resolving the size-protection contradiction.
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
Enables efficient formation of a cavity within the concrete, allowing for stress application to the tendon and subsequent filling with protective material, while ensuring effective removal of the pocket former and enhanced protection against corrosion and fire.
Implementation Method 1
The pocket former also includes a collapsible element, the collapsible element flexibly coupled to the inner portion and the outer portion of the pocket former body.
Implementation Method 2
The pocket former also includes a collapsible element, the collapsible element pivotably coupled to the pocket former body.
Data Source
Figure 1A~1B
Figure 1C~1E
Figure 2A~2B
AI summary
A pocket former may include a pocket former body, the pocket former body having an outer surface. The pocket former may further include a collapsible element, the collapsible element formed on the outer surface of the pocket former body. The collapsible element may extend radially outwardly from the pocket former body.