Distributed-Load Hold-Down Assembly for Wood Wall Uplift
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Solution Overview
Problem
Existing tension hold down systems in light frame and wood frame construction fail to effectively resist uplift and compensate for wood shrinkage, leading to instability and potential structural damage during storms, hurricanes, or earthquakes.
Innovation Solution
A hold down system comprising a tie-rod anchored to a concrete foundation, extending through openings in rigid members, with a slack absorber assembly that includes expansion devices and washers to maintain tension and distribute load, ensuring the tie-rod remains under tension and the wall is securely anchored.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional hold down system is used, then the structure is simple, but it fails to effectively resist uplift and compensate for wood shrinkage
Solution Approach 1:
The hold down system is divided into multiple functional segments: a tie-rod for tension resistance, a rigid member with openings for load distribution, expansion devices for compensating wood shrinkage, and washers for load distribution. Each segment performs a specific function, collectively providing reliable uplift resistance while managing complexity through modular design.
Solution Approach 2:
The system incorporates dynamic elements including the expansion devices that can expand to compensate for wood shrinkage over time, and the tie-rod that maintains tension as conditions change. This dynamic capability allows the system to adapt to environmental changes while maintaining reliability.
2Reliability
If a traditional hold down system is used, then the installation is simple, but it causes instability during storms, hurricanes, or earthquakes
Solution Approach 1:
The system is pre-assembled with the tie-rod, rigid member, expansion devices, and washers configured before installation. The tie-rod is positioned to extend through predetermined openings in the rigid member, and the expansion devices are pre-positioned to compensate for future wood shrinkage. This preliminary configuration ensures structural stability while simplifying the actual installation process.
Solution Approach 2:
The rigid member features localized openings positioned at specific locations to optimize load distribution. The expansion devices are placed at critical points where wood shrinkage occurs, providing targeted compensation. This localized quality approach enhances structural stability without requiring complete system redesign.
3Strength
If load is concentrated at a single point, then the connection is simple, but it leads to potential structural damage
Solution Approach 1:
The load path is segmented through multiple contact points: the tie-rod contacts the rigid member through openings, the expansion devices contact the wood frame at multiple locations, and the washers distribute load across broader surfaces. This segmentation of the load path prevents concentration at a single point, enhancing strength while using standardized components.
Solution Approach 2:
The system transitions from point-contact to area-contact load distribution by incorporating washers that spread loads over broader surfaces, and expansion devices that contact the wood frame at multiple spatial locations. This dimensional expansion of contact areas improves load distribution without requiring fundamentally new component types.
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 system effectively resists uplift and shear forces, compensates for wood shrinkage, and maintains structural integrity by distributing load through expansion devices and washers, ensuring the tie-rod remains under tension and the wall is securely anchored.
Implementation Method 1
the nut exerting pressure on the second rigid member to place the tie rod under tension loading, the tension loading is transferred by the second rigid member to the first and second supports
Implementation Method 2
thereby causing the first rigid member to press on the horizontal member of the stud wall via the first and second lateral sections of the first rigid member, thus distributing the compression loading
Data Source
AI summary
A hold down system for a building wall comprises a first rigid member and a second rigid member, the second rigid member being vertically spaced apart from the first rigid member, the first rigid member is supported on a horizontal member of a stud wall, the first and second rigid members including first and second openings, respectively; a tie-rod with a lower end portion for being anchored to an anchorage, the tie-rod extending transversely through the first and second openings, the tie-rod dividing the first and second rigid members into a first lateral section on one side of the tie-rod and a second lateral section on a diametrically opposite side of the tie-rod; first support and second support disposed between the first and second rigid members, the first support being disposed in the first lateral section, the second support being disposed in the second lateral section, the tie-rod extending through the first and second rigid members outside of the first support or the second support; and a nut threaded to the tie-rod, the nut exerting pressure on the second rigid member to place the tie rod under tension loading, the tension loading is transferred by the second rigid member to the first and second supports to subject the first and second supports to compression loading, thereby causing the first rigid member to press on the horizontal member of the stud wall via the first and second lateral sections of the first rigid member, thus distributing the compression loading.