Low-Profile Concrete Post-Tensioning Device
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Solution Overview
Problem
Conventional methods for repairing cracked concrete, such as doweling, epoxy injection, and post-tensioning, are either impractical, ineffective, or result in high-profile mechanisms that protrude from the concrete surface, failing to adequately restore tensile strength and prevent future cracking.
Innovation Solution
A low-profile tensioning device with an elongated body, stitch catch arm, and anchor, where the anchor interface surface tapers towards the catch arm end, allowing for axial force transfer across cracks, enabling effective post-tensioning without a large protruding mechanism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional post-tensioning is used to repair fractured concrete, then tensile strength is restored and cracks are closed, but a large high-profile mechanism protrudes from the concrete surface
Solution Approach 1:
The invention transitions from a vertical/high-profile anchorage system to a horizontal/low-profile system by placing anchorages within the concrete thickness. The tensioning device extends horizontally across the crack rather than vertically protruding, moving the solution from one spatial dimension to another.
Solution Approach 2:
The anchorages are nested within the concrete member thickness, with the elongated body of the tensioning device contained inside the concrete. The stitch catch arm and anchor aperture are positioned within the concrete cross-section, embedding the entire post-tensioning mechanism within the existing structure rather than adding external protrusions.
2Reliability
If conventional post-tensioning is used to repair fractured concrete, then structural stability is improved, but the tensioning mechanism inhibits future use of the slab
Solution Approach 1:
The entire post-tensioning mechanism is nested within the concrete member, with anchorages positioned inside the slab thickness. This internal placement eliminates external protrusions that would interfere with future slab operations, allowing the slab to be used for its intended purpose without obstruction.
Solution Approach 2:
The invention concentrates the post-tensioning function locally at the crack location within the concrete thickness, rather than requiring a distributed external mechanism. The anchorages are positioned only where needed to address the crack, leaving the rest of the slab surface clear for future use.
3Force
If doweling is used to repair cracks, then load transfer is achieved, but the method is impractical for typical slab thicknesses of 8 inches or less
Solution Approach 1:
The invention changes the geometric parameters of the anchorage system to suit thin slab applications. The anchor aperture and stitch catch arm are designed with dimensions appropriate for 8-inch or less slab thicknesses, unlike conventional dowels which require greater thickness for effective installation and load transfer.
4Strength
If epoxy injection is used to strengthen cracks, then crack strength is increased, but bond separation occurs under loading
Solution Approach 1:
The invention introduces a mechanical intermediary system (elongated body with anchorages) that mediates the load transfer across the crack. Rather than relying solely on epoxy bond strength, the mechanical anchorages provide a reliable physical connection that transfers tension loads without depending on epoxy-concrete bond durability.
Data Source
AI summary
A tensioning device and method for post-tensioning a concrete member having at least one crack is provided. The tensioning device may include an elongated body, a stitch catch arm and an anchor. The catch arm may be perpendicularly joined to one end of the elongated body, wherein the catch arm is inserted into a hole in the concrete member. The elongated body may form an anchor recess therein, wherein an anchor interface surface is defined by the anchor recess. The anchor interface may form an anchor aperture for receiving the anchor. The thickness of the anchor interface may uniformly decrease as the anchor interface extends toward the catch arm end of the anchor recess so that when ratcheting the anchor into the concrete member and onto the anchor interface a portion of the applied compressive force and/or torque may be transformed into an axial force along the elongated body so as to provide post-tensioning through the tensioning device and across the at least one crack.