Precast Segment Duct Sealing with UHPFRC Recesses
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Solution Overview
Problem
Existing solutions for connecting post-tensioning tendon ducts in precast concrete segmental structures often fail to achieve reliable and repeatable air-tightness, especially when tendons are inclined, and can be costly and complex, with some couplers not meeting the required air tightness test standards.
Innovation Solution
A method using Ultra High Performance Fibre Reinforced Concrete (UHPFRC) to create an air-tight connection between duct ends by pouring sealing material into recesses around the duct ends, preventing ingress into the ducts, and utilizing a thermo-retractable sleeve or other sealing mechanisms to ensure air-tightness, even for inclined tendons.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional couplers are used to connect duct ends, then air tightness may be achieved in some cases, but the device complexity increases and cost increases
Solution Approach 1:
The invention extracts the sealing function from complex mechanical couplers and transfers it to a simple sealing element (grommet or membrane) that is integrated into the recess structure. The duct ends are simply inserted into recesses that contain the sealing element, eliminating the need for complex coupler assemblies while maintaining air tightness.
Solution Approach 2:
The sealing solution applies local quality by placing a sealing element (grommet or membrane) specifically at the critical interface where the duct end meets the recess. This localized sealing approach provides effective air tightness without requiring the entire coupling mechanism to be complex, addressing the sealing need precisely where it is required.
2Reliability
If complex multi-component couplers are used, then air tightness may be improved, but the ease of manufacture deteriorates
Solution Approach 1:
The invention merges the sealing function with the recess structure itself. The sealing element is integrated into the recess during segment casting or installation, combining what were previously separate components (coupler body and sealing element) into a unified, simpler assembly that is easier to manufacture and install.
Solution Approach 2:
The sealing element is pre-installed in the recess before the duct end is inserted. This preliminary action ensures that the sealing is already in place and properly positioned, eliminating the need for complex assembly operations during the coupling process and significantly easing manufacture and installation.
3Ease of manufacture
If sealing material is poured into recesses without proper sealing mechanisms, then the process becomes simple, but grout may escape and air tightness fails
Solution Approach 1:
The sealing element (grommet or membrane) acts as an intermediary between the duct end and the recess. It allows the simple pouring process to continue while preventing grout escape and maintaining air tightness. The intermediary element bridges the gap between process simplicity and sealing reliability.
4Ease of manufacture
If no sealing material is used at duct junctions, then the process is simple and cost-effective, but air tightness and corrosion protection are compromised
Solution Approach 1:
The invention uses flexible sealing elements (grommets or membranes) that conform to the duct end geometry and create an effective seal. These thin film elements provide reliable corrosion protection and air tightness while maintaining process simplicity and cost-effectiveness, avoiding the need for complex rigid sealing structures.
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 method consistently passes the 0.1 bar air tightness test with durability and cost-effectiveness, providing a reliable and simple solution for duct continuity that meets the required standards without the need for complex couplers.
Implementation Method 1
pouring a sealing material into the recesses of the two consecutive segments around the duct ends while preventing the material to enter the internal space of the ducts
Implementation Method 2
utilizing a thermo-retractable sleeve or other sealing mechanisms to ensure air-tightness
Data Source
Figure 1~3
Figure 4~6
Figure 7A~7C
AI summary
A method for establishing an air-tight connection between post-tensioning tendon ducts (20) of two consecutive precast segments (10) of a structure, each segment (10) being cast with a recess (40) opening out on a jointing face (14;15) of the segment leaving an access to ends of the ducts (20), the method comprising: c) Connecting pairs of respective duct ends (20) of the two consecutive segments (10) together, and d) pouring a sealing material into the recesses (40) of the two consecutive segments around the duct ends (20) while preventing the material to enter the internal space of the ducts, thus forming an air-tight connection at the junction of ducts.