Hollow Profile Joint With Internal Nuts for Robust Connections
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Solution Overview
Problem
Existing joint structures for cold-formed profiles face challenges in achieving robustness and strength, especially under cyclic loading and in unconventional designs, due to limitations in material thickness, access for bolted connections, and potential for brittle failure modes.
Innovation Solution
A joint structure comprising first and second structural members with hollow cross-sections, secured by threaded bolts and nuts, and supported by fixing plates, which allows for efficient transfer of forces and moments while minimizing the need for complex welding and maximizing design flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If cold-formed profiles are used to reduce manufacturing complexity and cost, then ease of manufacture is improved, but the robustness and strength of joints under cyclic loading deteriorates due to limited material thickness and brittle failure modes
Solution Approach 1:
The joint is segmented into multiple functional components: fixing plates attached to structural members, threaded bolts for connection, and threaded nuts for securing. This segmentation allows each component to be optimized independently - fixing plates provide bearing surfaces, bolts provide tensile strength, and nuts provide locking capability - thereby achieving robust joints while maintaining the ease of manufacture associated with cold-formed profiles.
Solution Approach 2:
Threaded nuts are preliminarily secured to the inner surfaces of the structural members before final assembly. This preliminary action ensures proper positioning and alignment during assembly, enables pre-tensioning of bolts to achieve desired clamp loads, and allows for quality control checks before field installation, thereby improving joint robustness without adding manufacturing complexity.
2Strength
If welded connections are used to achieve strong joints, then strength is improved, but the harmful effects of heat input on material strength and durability worsen
Solution Approach 1:
The patent replaces the thermal welding process with a mechanical fastening system consisting of threaded bolts and nuts. This substitution eliminates heat input entirely, avoiding the detrimental effects on cold-formed profile material strength and durability while still achieving robust joint connections through mechanical interlocking and friction.
Solution Approach 2:
Fixing plates serve as intermediary elements between the structural members and the bolted connections. These plates distribute loads over larger areas, provide bearing surfaces that prevent direct contact between mating members, and enable the use of high-strength fasteners without concentrating stresses that could lead to failure in the cold-formed profiles.
3Object-affected harmful factors
If bolted connections are used to avoid welding heat effects, then harmful heat factors are reduced, but the strength and robustness of joints deteriorates due to limited access for applying threaded nuts
Solution Approach 1:
Instead of the conventional approach of attaching nuts to the outer surfaces of structural members (which requires access from both sides), the patent inverts the arrangement by securing threaded nuts to the inner surfaces. This inversion allows nuts to be installed from the interior of the structure, eliminating the need for difficult field access operations while maintaining full thread engagement and connection strength.
Solution Approach 2:
The threaded nuts are nested within the hollow cross-sections of the cold-formed profile structural members. This nesting arrangement allows the nuts to be positioned inside the profiles, utilizing the internal space for connection purposes without increasing external dimensions or requiring access to hard-to-reach exterior locations, thereby facilitating easier installation while maintaining joint robustness.
4Ease of operation
If self-tapping screws are used as alternative to bolted connections for difficult access locations, then ease of operation is improved, but the strength and robustness of joints deteriorates due to brittle failure modes
Solution Approach 1:
The patent employs threaded bolts and nuts that serve multiple functions: they provide strong tensile and shear resistance, enable adjustable clamping forces, allow for disassembly and reassembly, and accommodate various structural member configurations. This universal fastening system replaces the need for specialized self-tapping screws in difficult access locations, maintaining ease of operation through standardized components while achieving superior joint strength and robustness.
Data Source
AI summary
Described is a joint structure comprising: a first and a second structural member, each structural member comprising a hollow cross-section defining at least a first wall, and an inner surface and an outer surface of the respective structural member; at least a first fixing plate extending along at least a part of a respective end portion of each of the first and second structural members, and adjacent the respective outer surfaces thereof; a plurality of threaded bolts extending through a corresponding one of a plurality of apertures in the first fixing plate and a corresponding one of a plurality of apertures in the respective first wall of each of the first and second structural members, each one of the plurality of bolts thread-wise engaging a corresponding one of a plurality of threaded nuts secured to the respective inner surface of the respective structural member at a location corresponding to the respective aperture in the respective first wall, such that the first fixing plate holds the first and second structural members in a pre-determined position relative to each other and transfers forces and moments between the first and second structural members. Also described is a method of forming a joint structure.