Sacrificial Core Cavity for Crack Origin Differentiation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for testing pre-stressed structures, such as strand ground anchors, face challenges in accurately assessing crack width and differentiation between cracks of different origins due to residual compressive stress and additional cracking induced during disassembly and excavation, making it difficult to distinguish between load-induced and other types of cracks.
Innovation Solution
A method involving a removable or sacrificial core to create a cavity within the hardened material, allowing a second hardening material to fill cracks, which can be used to identify and differentiate cracks originating from loading, disassembly, or other sources without requiring drilling, using a curable liquid with suitable additives for efficient filling and visualization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the steel frame and external grout are removed to assess inner grout cracks, then crack width measurements can be obtained, but additional cracks are induced and residual compressive stress creates false cracks
Solution Approach 1:
The cavity is created and the second material is injected into it before the loading test is performed. This preliminary preparation allows the second material to be in position to fill cracks before they form, preventing the formation of false cracks during the testing and disassembly process.
Solution Approach 2:
The second hardening material acts as an intermediary substance that is injected into the cavity and cracks. It has different properties from the first material and can be visually distinguished, allowing clear differentiation between load-induced cracks and other types of cracks while filling and sealing the crack paths.
2Ease of operation
If the core is removed after the first material hardens, then a cavity is created for injecting the second material, but the removal process itself may induce additional cracks
Solution Approach 1:
The core is designed as a temporary, disposable element that is removed after serving its purpose of creating the cavity. It is sacrificed to enable the injection of the second material, and its removal is performed carefully to minimize damage to the surrounding first material.
Solution Approach 2:
The cavity is created and prepared before the loading test and crack formation. By having the cavity ready in advance, the need for invasive removal operations after loading is eliminated, preventing additional cracks from being induced during the assessment process.
3Strength
If residual compressive stress is present in the inner grout body, then the grout maintains structural integrity during loading, but longitudinal cracks form upon unloading and frame removal
Solution Approach 1:
The residual compressive stress, which normally causes harmful longitudinal cracks upon unloading, is converted into a benefit by having the second material already present in the cavity and cracks. When the stress-induced cracks form, the second material fills them, transforming the harmful cracking effect into a useful marking and sealing mechanism.
Solution Approach 2:
The second material serves as an intermediary that mediates between the residual compressive stress and the final crack pattern. It is injected into the cavity before unloading, positioned to intercept and fill any cracks that may form due to stress release, thereby capturing the true load-induced crack pattern.
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 reliable crack width and distribution measurements, allowing for clear differentiation between cracks of different origins, ensuring accurate assessment without causing additional damage, and facilitating compliance with standards like EN 1537 without the need for special molds.
Implementation Method 1
filling a hardening and/or hardenable second material into the at least one cavity created
Implementation Method 2
permitting or causing said second material to harden while maintaining the load
Data Source
Figure 1~3
AI summary
Method of testing a structure comprising the steps of providing at least one ten-sile element, providing at least one removable and/or sacrificial core, arranging the core at a position where a cavity is to be created, embedding the at least one tensile element and the at least one core in a first hardening and/or hardenable material, allowing or causing said first material to harden, creating at least one cavity in the first material by removing at least one core from the hardened first material if necessary, applying a load to the structure to a predetermined load level and maintaining said load level, filling a hardening and/or hardenable second material into the at least one cavity created, permitting or causing said second material to harden while maintaining the load, and removing the load from the structure after the second material has reached a compressive strength that is at least equal to the compressive strength of the first material.