Ai-lin, Ran, Zi-qin, and Zhen-yu, 2018
The seismic performance of a prefabricated beam-column steel connection (PBCSC) with flange cover plates was observed through six full scale test specimens under cyclic loading and fatigue testing. The experimental investigation of the PBCSC specimens revealed that the plastic damage of the system after seismic loading was concentrated into the replaceable flange and cover plate components, and that the energy dissipation was performed by the plastic deformation of replaceable components and by frictional damping between the beams and cover plates.
System Concept
The system proposed in this study involves a prefabricated beam-column steel connection (PBCSC) connection in which all welded connections are fabricated in a factory in order to facilitate construction with no on-site welding. The connection is between a circular tube steel column attached to a cantilevered beam and the adjacent H shaped independent beam. A flange cover plate with a dog bone is bolted to the top and bottom of the connection between the beams. A gap is left between the two beam components in order to allow for some rotation under the load application.
The system is designed to remain elastic after application of lateral loads with the exception of the cover plates, which are designed to dissipate seismic energy through plastic deformation. Because of the bolted connections between the cover plates and the beam connections, the cover plates are designed to be easily replaceable after seismic loading, which would allow for the system to regain its load capacity after seismic events without significant structural damage to remaining components. Additionally, brass friction plates were included in some of the test specimens between the cover plates in order to increase the seismic energy dissipation capacity of the system through frictional damping.
Experimental Study, Results, and Discussion
The testing consisted of six full scale beam and column subassemblies featuring the PBCSC connection. The column was a 299x16 mm steel pipe, while the beam was a 300 × 200 × 6 × 12 mm H-shaped steel beam. The designs of the test specimens included original and repaired cover plate connections in order to test the repairability of the system after a seismic event. Two of the test specimens also included brass friction plates between the cover plates.
The columns were mounted horizontally in the reaction frame, where the right end was hinged and the left end was hinged to a hydraulic jack and fitted with a force sensor. The free end of the beam was connected to a hydraulic jack to supply lateral cyclic loads, and included both a force sensor and a displacement meter. The hydraulic jack applied displacement-informed cyclic loading to the test specimen with six cycles at displacements of 0.375%, 0.5%, 0.75%, four cycles at 1%, and two cycles at 1.5%, 2%, and finally 2 cycles at increasing displacements by 1%. The testing was terminated when the specimen failed, the beam rotation angle exceeded 0.05 radians, or the load at the end of the beam was greater than the ultimate load and experienced decreases of less than 85%.
The experimental study revealed that the test specimen achieved energy dissipation through the plastic deformation of the cover plates at the beam connection, as well as slip friction between the plates and the beams. The structural damage was concentrated to the replaceable fuse cover connections, which was indicated to be replaceable due to the performance of the repaired specimens. The cantilevered beam was also kept free of structural damage by increasing its thickness. Plastic deformation occurred at the dog bone of the flange cover plate, therefore the seismic design was able to prevent structural damage to other components of the frame system.
Reference
Ai-lin, Z., Ran,L ., Zi-qin, J., and Zhen-yu, Z. (2018). “Experimental study of earthquake-resilient PBCSC with double flange cover plates,” Journal of Constructional Steel Research, 143. pp. 343-356.