Zhang, Xu, Li, 2023
This study introduces a novel approach to self-centering modular steel structure connection (SC-MCSS) to improve seismic performance while incorporating a simple plug-in construction process. The proposed system includes diagonal self-centering (SC) haunch braces at the connection core ensuring minimal deformation by coordinating with the modules through connecting components. The SC haunch brace comprises disc springs and sliding tubes which allows a great self-centering capacity and bearing capacity of the system while increasing overall load distribution. The system was subjected to axial cyclic loading tests to validate its seismic bearing capacity including hysteretic responses, energy dissipation, resulting deformation, and strain features. The overall test results of the specimens and flag-shaped hysteresis curves indicated satisfactory energy dissipation capacity and self-centering property of the system. It was observed that the post-activation stiffness of the disc springs is a significant factor when determining the performance of the connections.
System Concept
The proposed system has three main parts which are the modules, connecting elements and the SC haunch braces. The hollow ends of the column modules are joined with a cross-shaped plug-in connector and fastened with bolts over cover plates. Diagonal SC haunch braces are secured to the gusset plates of the column to provide a hinge connection and an internal force transmission path. The self-centering (SC) haunch brace includes inner and outer tubes, pre-compressed combined disc springs, mobile spring plates and blocking plates attached to the end of the tubes. Initially, load was resisted by the tenons of the connector in the columns followed by the activation of haunch braces when a load greater than prestressed force of the springs is exerted. This then causes the two nested tubes to move, and further compresses the disc springs for both compression and tension states of the brace. The device then returns to original position with no degradation of strength after load is removed. The other significant role of the SC haunch brace is to allow greater load distribution with the aim of reducing critical damage by concentrating it away from the connection core.
Experimental Study, Results and Discussion
Experimental tests were conducted on both SC haunch brace specimens and the SC-MSS connection specimens. The SC haunch braces, under pure axial load, successfully generated hysteretic curves with no residual deformation or strength degradation with noticeable energy dissipation by friction between the contact surfaces. Three ¾ scale T-shaped connection specimens underwent quasi-static cyclic loading tests to evaluate their hysteretic responses, energy dissipation and residual deformation. It was observed that all specimens generated flag-shaped hysteretic curves with stable energy dissipation capacity and excellent self-centering ability. The SC-MSSC2 specimen with a higher post-activation stiffness, achieved the most remarkable seismic performance including strength, energy dissipation and residual drift ratios. The results of both sets of tests validated the reliability of the proposed system proving it to be a promising innovation with great seismic response as well as better recoverability due to its plug-in integration technology.
Reference
Zhang, G., Xu, L., & Li, Z. (2023). Development and Experimental Verification of Self-Centering Haunched Plug-In Modular Connections. Journal of Structural Engineering, 149(5), 04023047. https://doi.org/10.1061/JSENDH.STENG-12029