Shallow Undercut Concrete Anchor for Limited Embedment Depth
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Solution Overview
Problem
Post-tensioned slabs require anchors that can securely attach objects like pipes to the slab with limited embedment depth due to the proximity of cables/wires to the surface, and existing anchors fail to consistently bear larger loads under standard test conditions.
Innovation Solution
A shallow undercut concrete anchor system featuring a sleeve and plug design with radially extending legs and an increasing diameter portion to lock into a ¾″ or less deep hole, providing dynamic radial outward force for secure anchoring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If post cast anchors are installed in PT slabs, then anchors can be installed after slab casting, but the embedment depth is limited to 3/4" or less due to cable proximity
Solution Approach 1:
The anchor transitions from relying solely on embedment depth (one dimension) to utilizing radial expansion into the concrete matrix (another dimension). The legs expand radially outward to create mechanical interlock, compensating for the limited axial embedment depth available in thin PT slabs with surface-proximity cables.
Solution Approach 2:
The anchor employs a dynamic expansion mechanism where the plug is inserted and then activated to force the legs radially outward. This dynamic transformation from a compact insertion state to an expanded locked state enables the anchor to achieve secure attachment despite the constrained 3/4" or less embedment depth.
2Length of stationary object
If anchors are installed with limited embedment depth, then cable proximity is accommodated, but load-bearing capacity is reduced
Solution Approach 1:
The anchor changes the stress distribution parameters within the concrete by expanding radially. Instead of relying on bond strength over a long embedment length, the system creates localized compressive stress zones around the expanded legs, transforming the load transfer mechanism to achieve high load-bearing capacity within 3/4" or less embedment depth.
Solution Approach 2:
The anchor system creates a composite structure combining the metal sleeve and plug with the concrete matrix. The expanded legs form a mechanical interlock that combines the strength of the metal components with the bonding and friction characteristics of the concrete, achieving superior load-bearing capacity despite limited embedment depth.
3Ease of manufacture
If conventional anchors are used in thin slabs, then installation is possible, but reliability is insufficient under seismic and dynamic loads
Solution Approach 1:
The anchor is designed to be dynamic rather than static, with legs that can expand and flex in response to applied loads. This dynamic capability allows the anchor to maintain reliability under seismic and dynamic loading conditions by adapting its grip strength, while remaining simple enough for straightforward post-cast installation.
Solution Approach 2:
The anchor is pre-assembled in a compact state for easy installation, then activated in situ to expand and lock. This preliminary preparation allows simple installation followed by reliable performance, as the expansion action creates the secure mechanical interlock needed for high-reliability attachment under various load conditions.
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 anchor system effectively resists large loads and maintains secure attachment in both un-cracked and cracked concrete, exceeding minimum load-bearing requirements under various test conditions, including seismic loads, with minimal displacement and high reliability.
Implementation Method 1
The plug includes an increasing diameter portion disposed toward a first end of the plug... The second end of the plug is received in the cylindrical through opening until the increasing diameter portion engages the legs
Implementation Method 2
Dynamic loading on the plug (e.g., via a threaded rod) when the anchor is in use generates a dynamic radially outward force on the legs to secure the anchor in the concrete hole
Implementation Method 3
After installation, legs of the sleeve extend radially outward past the wall and the increasing diameter portion prevents inward movement of the legs to lock the sleeve and the plug in turn in the concrete cylindrical opening
Data Source
AI summary
A concrete anchor capable of resisting large loads while requiring minimal embedment depth. The system includes a concrete structure including a cylindrical opening in the concrete surface thereof. The system also uses an anchor which includes a sleeve and a plug. The sleeve includes at least two legs extending toward a first end of the sleeve. The plug includes an increasing diameter portion disposed toward a first end of the plug. The plug includes a locking opening. After installation, legs of the sleeve extend radially outward past the wall and the increasing diameter portion prevents inward movement of the legs to lock the sleeve and the plug in turn in the concrete cylindrical opening. Furthermore, dynamic loading on the plug via the locking opening when the anchor is in use generates a dynamic radially outward force on the legs to secure the anchor in the concrete hole.