Shallow Undercut Concrete Anchor for Low-Depth High-Load Fixing
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Solution Overview
Problem
Post-tensioned slabs require anchors that can securely attach objects like pipes to the slabs with limited embedment depth due to the proximity of cables/wires to the surface, and existing anchors fail to consistently bear larger loads, especially in cracked concrete.
Innovation Solution
A shallow undercut concrete anchor system featuring a sleeve and plug design with radially extending legs and an increasing diameter portion that locks into a cylindrical opening in the concrete, providing dynamic radial outward force to secure the anchor and resist pull-out forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If post cast anchors are drilled into set concrete, then anchors can be installed after slab casting, but the embedment depth is limited to 3/4" or less due to cable proximity to surface
Solution Approach 1:
The anchor transitions from a simple cylindrical form to an undercut geometry where the embedded portion has a smaller diameter than the exposed portion. This dimensional change in the anchor's cross-section allows the anchor to engage concrete at multiple depths and provides mechanical interlock that compensates for the limited embedment depth constraint.
Solution Approach 2:
The anchor is divided into distinct functional segments: an embedded portion for concrete engagement, an undercut portion that creates mechanical interlock, and an exposed portion for load application. This segmentation allows each portion to optimize its function within the constrained embedment depth while collectively achieving high load-bearing capacity.
2Reliability
If embedment depth is limited to 3/4" or less, then cable damage is avoided, but anchor load-bearing capacity is reduced
Solution Approach 1:
The anchor incorporates curved and tapered surfaces, particularly in the undercut transition zones, that distribute stresses more effectively than sharp angles. The curved geometry of the embedded portion optimizes stress distribution in the concrete while the tapered exposed portion efficiently transfers applied loads into the concrete substrate despite limited embedment depth.
Solution Approach 2:
The anchor system effectively creates a composite structure where the metal anchor body and concrete substrate work together as an integrated load-bearing system. The undercut geometry ensures intimate contact and mechanical interlock between the two materials, allowing them to function as a unified structure that achieves high load capacity within the 3/4" depth constraint.
3Ease of manufacture
If conventional anchors are used in cracked concrete, then installation is simple, but load-bearing reliability is insufficient
Solution Approach 1:
The anchor's undercut geometry is designed in advance to anticipate and counteract the presence of cracks in the concrete. The expanded exposed portion and undercut features create multiple mechanical interlock points that remain effective even when cracks develop, preventing the anchor from becoming dislodged or losing load-bearing capacity due to concrete cracking.
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 with a ¾″ embedment depth or less, maintaining stability in both un-cracked and cracked concrete, exceeding minimum load-bearing standards and ensuring reliable attachment in various installation conditions.
Implementation Method 1
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
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.