Deck Joist Grooves and Polymer Inserts Prevent Corrosion
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Solution Overview
Problem
The existing methods for attaching deck boards to aluminum joists are prone to shear failure due to seasonal movement, galvanic corrosion, and require pre-drilling, which can lead to cosmetic flaws and increased costs.
Innovation Solution
A deck board supporting system with interconnected skirt joists and deck joists featuring longitudinal grooves on their top surfaces for receiving fasteners, along with plastic inserts to prevent corrosion and allow for expansion/contraction without sacrificing grip force, eliminating the need for pre-drilling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If pre-drilled holes are used to attach fasteners to aluminum joists, then the attachment process is simplified, but galvanic corrosion occurs between stainless fasteners and aluminum joists
Solution Approach 1:
A polymer insert is introduced as an intermediary component between the metal fastener and the aluminum joist. The fastener is inserted into the pre-drilled hole, and the polymer insert is then placed over the fastener shaft, electrically isolating it from the aluminum joist surface to prevent galvanic corrosion while maintaining the simplicity of the pre-drilled hole attachment method
Solution Approach 2:
The attachment system uses a composite structure combining metal fastener, polymer insert, and aluminum joist. The polymer insert acts as a dielectric material that prevents direct contact between dissimilar metals, eliminating the galvanic cell formation while maintaining mechanical fastening strength
2Productivity
If pre-drilled holes are used for fastener attachment, then installation is faster, but seasonal movement causes shear failure of fasteners
Solution Approach 1:
The polymer insert is designed with flexible properties that allow it to dynamically adjust to seasonal expansion and contraction of the deck boards. The insert can deform elastically with the board movement while maintaining continuous contact with the fastener, preventing shear failure without requiring complex adjustment mechanisms
Solution Approach 2:
The polymer insert material is selected with specific viscoelastic properties that allow it to change its mechanical parameters (stiffness, damping) in response to environmental conditions and load variations, providing consistent fastener retention despite seasonal dimensional changes in the deck structure
3Strength
If hole size is reduced to prevent fastener breaking, then fastener integrity is improved, but grip force on the fastener is reduced
Solution Approach 1:
The polymer insert provides localized reinforcement and friction engagement along the entire length of the fastener shaft within the joist, rather than relying solely on the end grain grip. This distributed local engagement maintains fastener integrity with appropriately sized holes while providing sufficient total grip force through cumulative friction along the insert-fastener interface
4Reliability
If timber battens are used to prevent shear failure, then fastener reliability is improved, but cost and installation time increase
Solution Approach 1:
The protective and load-distributing function previously requiring separate timber batten components is extracted and integrated directly into the polymer insert that is already part of the fastening system. This eliminates the need for additional battens while maintaining shear failure prevention through the insert's inherent mechanical properties and fastener-joining capability
Data Source
AI summary
A deck board supporting system includes a plurality of interconnected skirt joists configured as an outer perimeter of the deck board supporting system and a plurality of deck joists configured to be attached to one or more of the plurality of skirt joists within the outer perimeter. Each of the skirt joist and deck joist has a respective longitudinal groove formed on a respective top surface, and the longitudinal groove extends downwards perpendicular to the respective top surface. The longitudinal groove is configured for receiving one or more fasteners for connecting one or more deck boards to the top surfaces of the respective skirt joists and deck joists.