Bi-Axial Beam-to-Column Joint Using Gusset Plates on HSS Columns
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Solution Overview
Problem
Conventional methods for connecting Hollow Structural Section (HSS) columns to wide flange beams in moment-resisting steel frames are inefficient, costly, and uncertain in performance, particularly under seismic loading, due to limitations in transferring moment forces through the thin walls of HSS columns.
Innovation Solution
A bi-axial beam-to-column joint connection using a prefabricated column assembly with interconnected gusset plates that extend orthogonally from the column, allowing for secure attachment of beams through bolts, thereby distributing moment resistance across all faces of the column and enhancing ductility and strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If direct welding of beam flanges to HSS column faces is used, then connection strength is improved, but the inherent flexibility of thin HSS walls limits moment transfer capacity and reliability
Solution Approach 1:
Diaphragm plates are introduced as intermediary elements between the beam flanges and the HSS column. These plates transfer moment forces to the column webs through reliable welds, overcoming the limitation of direct welding to thin HSS faces. The diaphragm plates act as mediators that distribute forces to the stiffer column web regions, improving both strength and reliability of moment transfer.
Solution Approach 2:
The connection design transitions from relying solely on the thin HSS column faces (one-dimensional surface) to utilizing the three-dimensional space within the column by inserting diaphragm plates. This allows moment forces to be transferred through a different spatial path - from beam flanges to diaphragm plates and then to the column webs, effectively bypassing the limitation of thin face walls.
2Strength
If through-plate connections are used to transfer moment forces, then moment transfer capacity is improved, but fabrication cost and complexity increase significantly
Solution Approach 1:
The connection system is segmented into distinct functional components: beam flanges, diaphragm plates, and column webs. This segmentation allows each component to be optimized independently and assembled through standardized connection details, reducing fabrication complexity compared to monolithic through-plate solutions while maintaining moment transfer capacity.
Solution Approach 2:
The diaphragm plates are designed as relatively simple, shop-welded components that can be fabricated economically. Rather than using expensive and complex field-welded through-plates, the diaphragm plates serve as disposable-like elements that provide the necessary moment transfer function at reduced fabrication cost and complexity.
3Strength
If HSS column wall thickness is increased to improve moment resistance, then connection strength is improved, but material cost and column weight increase
Solution Approach 1:
Diaphragm plates serve as intermediaries that enable efficient moment transfer without requiring increased HSS wall thickness. The plates distribute moment forces to the column webs, allowing the use of thinner, lighter HSS columns while maintaining adequate moment resistance capacity.
Solution Approach 2:
The connection design changes the force transfer mechanism parameters - instead of relying on the HSS wall thickness parameter alone, the system utilizes the diaphragm plate geometry and weld configuration parameters to achieve moment resistance. This allows optimization of column weight independently of moment capacity requirements.
4Device complexity
If conventional uniaxial connection methods are used, then design simplicity is maintained, but performance under seismic loading and bi-axial moments is insufficient
Solution Approach 1:
The diaphragm plate connection system is designed to perform multiple functions: it transfers moments in both uniaxial and bi-axial directions, provides ductility under seismic loading, and maintains design simplicity. The same basic diaphragm plate configuration handles various loading scenarios, making the connection universally applicable and reliable for seismic performance.
Data Source
AI summary
A prefabricated column assembly includes a hollow tubular column having a longitudinal axis. A gusset plate assembly includes a plurality of gusset plates connected to the column and extending laterally outward from the column in planes generally parallel to the longitudinal axis of the column. A first pair of the gusset plates extends laterally outward from the column along a first axis and defines a space for receiving an end portion of a first beam for mounting the first beam on the first pair of gusset plates. A second pair of the gusset plates extends laterally outward from the column along a second axis that is nonparallel and non-coincident with the first axis. The second pair of gusset plates defines a space for receiving an end portion of a second beam for mounting the second beam on the second pair of gusset plates to provide a bi-axial joint connection.