Split-Sleeve Fastener for Seismic Anchoring in Cracked Concrete
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Solution Overview
Problem
Conventional drop-in anchors fail to meet seismic and cracked concrete requirements due to limited outward expansion of segments, leading to safety risks and damage to the target structure's walls during installation and potential sliding issues under stress.
Innovation Solution
A fastener design featuring a tubular main body with a split portion having a tapered section and an expansion sleeve that extends to the lower end of the tapered section, allowing for enhanced outward expansion and secure engagement with the target structure, while minimizing friction and damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the expansion sleeve only surrounds the neck and upper part of the tapered portion (as in conventional designs), then the installation process is simpler, but the outward expansion is insufficient and projections are needed which damage the hole walls
Solution Approach 1:
The expansion sleeve is divided into multiple segments that can expand outward independently. This segmentation allows the sleeve to expand uniformly without requiring damaging projections, resolving the contradiction between simple installation and sufficient expansion capability.
Solution Approach 2:
The expansion sleeve extends to the lower end of the tapered section, utilizing the longitudinal dimension to maximize expansion capability without adding radial projections. This dimensional extension provides sufficient outward expansion while maintaining smooth hole wall contact.
2Strength
If the expansion sleeve extends beyond the tapered portion, then outward expansion is enhanced, but friction and contact resistance prevent smooth backward sliding under seismic or crack conditions
Solution Approach 1:
The expansion sleeve extends exactly to the lower end of the tapered section, providing just enough expansion capability without excessive extension that would cause friction. This precise positioning allows smooth sliding while maintaining sufficient expansion strength.
3Strength
If projections are formed on the expansion sleeve outer surface to achieve tight engagement, then frictional engagement is improved, but the projections damage the hole walls during installation and expansion
Solution Approach 1:
The expansion sleeve acts as a flexible shell that expands uniformly to create frictional engagement without rigid projections. This flexible design maintains tight engagement with the hole walls while avoiding concentrated stress points that would cause damage during installation and expansion.
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 design ensures sustained outward expansion and reliable locking engagement, even under seismic conditions or with cracked concrete, by allowing smooth relative sliding between the fastener body and expansion sleeve, thereby enhancing safety and stability.
Implementation Method 1
a tapered expansion piece is forced into the tapered hole when the anchor screw is inserted into the tapped end of the dowel. The tapered expansion piece forces the slotted end of the split portion radially outwards. This deformation is transmitted to the sleeve so that it is pressed against the hole surface
Implementation Method 2
the contact between the lower edge of the expansion sleeve and a side surface of the tapered portion, or the friction between the walls of the hole and the uncovered tapered portion of the anchor body, might hold up a backward sliding of the anchor body with respect to the expansion sleeve
Data Source
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AI summary
A fastener includes a main body having a tubular portion and a split portion that extends from a lower end of the tubular portion, and longitudinally includes a tapered section that tapers in a direction towards the tubular portion. The fastener further includes an expansion sleeve annularly surrounding the split portion, wherein the expansion sleeve longitudinally extends to a lower end of the tapered section.