Ball-Expanded Anchor Structure to Prevent Concrete Cone Failure
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional expansion anchors face limitations in achieving high withdrawal resistance while preventing cone-type failure, where the expansion of the radially expansive portion can lead to a cone-shaped failure in concrete structures, especially under downward loads.
Innovation Solution
The expansion anchor features a hollow shaft with a radially expansive portion formed by axially elongated slits, which is bulged by a multiplicity of metal balls, allowing for deep biting engagement with the installation region without excessive compressive force, thereby enhancing withdrawal resistance and preventing cone-type failure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the radially expansive portion is expanded into a flaring shape to increase withdrawal resistance, then withdrawal resistance is improved, but cone-type failure occurs in the concrete structure
Solution Approach 1:
The radially expansive portion is divided into multiple segments by longitudinal slits, allowing it to expand in a controlled manner that prevents excessive localized pressure on the concrete, thereby avoiding cone-type failure while maintaining withdrawal resistance
Solution Approach 2:
The expansion is localized to specific regions through the slit configuration, creating targeted expansion zones that provide anchoring force without distributing excessive compressive stress across the entire concrete structure, preventing cone-type failure
2Object-affected harmful factors
If the radially expansive portion is prevented from excessive expansion to avoid cone-type failure, then cone-type failure is prevented, but withdrawal resistance is reduced
Solution Approach 1:
The expansion mechanism is made dynamic and controllable through the slit design, allowing the radially expansive portion to expand to an optimal degree that provides sufficient withdrawal resistance while preventing excessive expansion that would cause cone-type failure
Solution Approach 2:
The geometric parameters of the slits (number, width, length) are optimized to control the expansion characteristics, enabling the system to achieve the right balance between withdrawal resistance and prevention of cone-type failure
3Strength
If a bolt is used to directly expand the radially expansive portion, then withdrawal resistance is achieved, but the structure is complex and difficult to install
Solution Approach 1:
The complex bolt mechanism is extracted and replaced with a simpler pin insertion method. The pin with a tapering tip portion provides the necessary expansion function through a straightforward impact insertion, eliminating the need for threading and tightening operations
Solution Approach 2:
The mechanical screwing action of a bolt is replaced with a simpler impact-driven insertion of a tapered pin, reducing installation complexity while maintaining the expansion function through geometric rather than threaded engagement
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
This design provides a high withdrawal resistance while preventing cone-type failure, allowing for reliable fastening and easy maintenance, with adjustable torque to maintain optimal withdrawal resistance and easy removal of the anchor.
Implementation Method 1
a radially expanding action member (10) which pushes the radially expansive portion (7) radially outward in response to pushing action caused by screwing of the bolt (9) into the hollow shaft (3)
Implementation Method 2
the radially expansive portion (7) comes into biting engagement with the pre-formed hole (2) in the installation region (1), thereby providing a resistance against withdrawal
Data Source
Figure 1(A)~1(F)
Figure 2(A)~2(D)
Figure 3(A)~3(E)
AI summary
An expansion anchor includes a hollow shaft 3 and a bolt 9 to be screwed thereinto from a base end side of the hollow shaft. The hollow shaft 3 is formed, at a portion thereof short of a tip end 3a, with a radially expansive portion 7 which includes slits 6, and a multiplicity of balls 10 are inserted into the radially expansive portion 7. When the bolt 9 is screwed, the balls 10 push against each other and move radially. As a result, the radially expansive portion 7 deforms expansively for securely engaging with a pre-formed hole 2. Even when the radially expansive portion 7 expands, stress does not concentrate at a specific portion of an installation region 1, so that it is possible to provide a high withdrawal resistance while preventing cone-type failure. The management of the withdrawal resistance can be easily performed by screwing the bolt 9 using a wrench with a torque limiter or by screwing the bolt 9 using a torque wrench.