CFST Column Connection to RC Footing via Rotational Interlock
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Solution Overview
Problem
Existing methods for connecting circular concrete-filled steel tubular (CFST) columns to reinforced concrete (RC) footings struggle to integrate with precast elements, failing to develop sufficient strength, stiffness, and ductility required for carrying gravity loads and seismic designs.
Innovation Solution
A method involving a reinforced concrete footing with a cavity and embedded tubular member, where the CFST column is anchored using an elliptical base plate with flange slots, allowing rotation for interlocking and securement, followed by concrete grouting and filling to enhance mechanical interlock and resistance to lateral loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional connection methods are used for CFST columns to RC footings, then the connection can be made, but the connection fails to develop sufficient strength, stiffness, and ductility required for carrying gravity loads and seismic designs
Solution Approach 1:
The patent embeds a tubular member within the RC footing cavity, creating a nested structure where the steel tube is partially embedded in concrete. This nesting allows the column to be integrated with the footing while maintaining the necessary strength and ductility for both gravity and seismic loads through the interaction between the embedded tubular member and the surrounding concrete.
Solution Approach 2:
The connection utilizes composite construction by combining steel (tubular member and CFST column) with concrete (footing and grout). This composite approach allows the connection to develop sufficient strength, stiffness, and ductility by leveraging the complementary properties of both materials working together to resist gravity and seismic loads.
2Stability of the object's composition
If the steel tube is embedded in the footing, then the column can be anchored, but the connection lacks the ductility cycles required for seismic designs
Solution Approach 1:
The patent employs a dynamic connection mechanism where the CFST column can rotate relative to the embedded tubular member during seismic loading. This rotational degree of freedom allows the column to undergo ductile cycles while maintaining anchorage stability, enabling the structure to dissipate seismic energy through controlled deformation rather than rigid fracture.
3Productivity
If precast elements are integrated with the connection, then construction efficiency improves, but the connection detailing becomes more complex
Solution Approach 1:
The connection system is segmented into distinct components: a precast RC footing with an embedded tubular member, a separate CFST column, and connection elements (flanges, slots, brackets). This segmentation allows each component to be manufactured independently using standardized details, improving construction efficiency while maintaining manageable complexity through modular assembly.
Data Source
AI summary
The method of connecting a circular concrete-filled steel tubular column to a reinforced concrete footing provides a process for constructing a circular concrete-filled steel tubular column anchored in a reinforced concrete footing. A tubular member is partially embedded in a cavity formed in a block of reinforced concrete, such that a pair of flanges thereof is positioned adjacent to and above a base surface of the cavity. A steel tube is partially inserted into the cavity, such that rotation of the steel tube will cause the pair of flanges to interlock with a pair of slots at the lower end of the steel tube, locking the steel tube in place with respect to the tubular member and the block of reinforced concrete. The cavity is filled with concrete grout to secure the column, and the steel tube is filled with concrete to form the circular concrete-filled steel tubular column.