Yieldable Joist Hanger Prevents Fastener Shearing
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Solution Overview
Problem
Conventional joist hangers face issues with fastener shearing due to uneven load distribution and misalignment during installation, leading to potential failure under shear loads.
Innovation Solution
A hanger design featuring yieldable portions with energy dissipation slots and staggered fastener holes that deform at loads below the shear capacity of the fasteners, allowing for relative movement and preventing screw shearing, while maintaining secure attachment to both the joist and header.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional rigid connection design is used, then structural strength is maintained, but fasteners are prone to shearing under load due to uneven load distribution and misalignment
Solution Approach 1:
The connection portion is designed with a yieldable region that changes the mechanical parameters of the connector, allowing it to deform elastically under load. This deformation capability redistributes shear forces more evenly across fasteners, preventing individual fastener overload and shearing while maintaining overall connection strength
Solution Approach 2:
The connector transitions from a rigid static structure to a dynamic system with elastic deformation capabilities. The yieldable region allows the connection to adapt its geometry under load, accommodating misalignment and uneven load distribution through controlled elastic deformation rather than rigid failure
2Ease of operation
If rigid connection design is used, then manufacturing precision is simplified, but installation alignment becomes difficult leading to fastener misalignment
Solution Approach 1:
The yieldable region acts as a pre-designed cushioning element that anticipates and accommodates alignment errors before they cause fastener misalignment or failure. This elastic deformation capacity compensates for installation tolerances and misalignment issues without requiring high manufacturing precision
Solution Approach 2:
The connector allows dynamic adjustment during installation through elastic deformation, enabling easier alignment and fastener insertion even when initial positioning is imprecise, thereby improving ease of operation without compromising the final connection integrity
3Strength
If larger fasteners are used to prevent shearing, then shear load capacity increases, but device complexity and installation difficulty increase
Solution Approach 1:
The yieldable region extracts and absorbs excess shear forces through elastic deformation, removing the need for oversized fasteners to handle peak loads. This allows the use of smaller, standard fasteners while maintaining adequate shear load capacity through the combined system of fasteners plus elastic deformation capability
Solution Approach 2:
The system changes the load-bearing mechanism from relying solely on fastener strength to a combined mechanism of fastener strength plus elastic deformation of the connection portion. This parameter change allows smaller fasteners to achieve the same effective shear load capacity as larger fasteners would provide in a rigid connection
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 effectively reduces shear lag and prevents fastener failure by accommodating load-induced movement through deformation of yieldable portions, ensuring secure and durable connections with smaller screws, thus enhancing structural integrity and ease of installation.
Implementation Method 1
Each yieldable portion is configured to change a dimension of the aperture by deforming at a load that is less than a shear load capacity of the fastener received through the aperture
Data Source
AI summary
A hanger for connecting a structural member to a structural support including a base sized and shaped for receiving the structural member thereon. First and second side panels extend upward from the base. First and second back panels each extend from a respective one of the side panels. First and second top flanges each extend from a respective one of the back panels. An opening in one of said first and second side panels and said first and second back panels is configured to receive a fastener to attach the hanger to one of the structural member and the structural support. A slot is adjacent the opening. An area between the opening and the slot defines a yieldable portion selected to deform at a load that is less than the shear load capacity of the fastener when received through the opening for connecting the hanger to one of the structural member and the structural support.