Hu, Wang, Qu, and Alam (2020)
A Self-centering Energy-Absorbing Dual Rocking Core (SEDRC) system is proposed with two rocking core systems pinned to the foundation of a building to remain ductile under seismic loading, post-tensioning applied vertically to provide self centering capabilities, and energy dissipating fuses to dissipate seismic energy. The proposed fuse, titled the shear friction spring damper (SFSD), was tested individually, then a 35% scale three story frame system was tested under cyclic loading, and a numerical model was created following the tests.
System Concept
The system is derived from a rocking core system with energy dissipation and post tensioning, but is novel due to a dual rocking core (RC) system located on either side of the frame. High strength bolts are used to pin the rocking cores to the foundation, and the system is designed such that the RCs will remain ductile and will cause the system to rock under the application of seismic loading. Post-tensioning strands are also applied to the system such that any horizontal deflection of the system is counteracted by a self centering force from the post-tensioning.
Shear friction spring dampers (SFSD) are located vertically along the RC’s and are connected through high strength bolts. The SFSD’s consist of an interior and exterior spring group that are interlocked to provide frictional damping under the application of seismic loading. The SFSD is preloaded with some initial force, and any force that is further applied to the system will cause a compression of the spring groups located between the two circular tubes, which would lead to a frictional force to dissipate the seismic load applied to the system.
Experimental Study, Results, and Discussion
The first test conducted on the Self-centering Energy-absorbing Dual Rocking Core (SEDRC) system was performed on individual frictional springs located in the shear friction spring damper (SFSD). The system consisted of two interior and two exterior rings concentrically assembled and loaded into a 500 kN universal testing machine. Displacement informed loading was performed on the specimen, and the loading was performed in increments of 2 mm up to 14 mm. The test concluded that the springs had a frictional coefficient of about 0.09.
Following the component testing of the SFSD, a 35% scale three story office building prototype using the SEDRC system was erected for cyclic testing. Each rocking core has three SFSD’s connected through high strength bolts. The target roof drift was designed to be 6%, and the interstory drift was considered to be uniform due to the stiffness of the rocking cores. An actuator connected to the frame, and the other end was connected to a loading beam, which was designed to apply reversed cyclic displacement to the system with three cycles set to a maximum drift of 0.25% measured by strain gauges and displacement transductors. The results of the experimental study confirmed that the deformation of the system occurred in the SFSD’s and that a flag shaped hysteretic response curve was generated from the rocking and self centering components of the system. The system was therefore able to undergo uniform interstory drift up to a 6% roof drift, with sufficient energy dissipation up to the MCE.
A numerical study was conducted of the system following the experimental test. The parameters of the study conducted were the same as those of the experimental test from the data collected. The numerical study exhibited a 1.65% interstory drift, with no residual deformations after loading.
Reference
Hu, S., Wei, W., Qu, B., and Alam, S. (2020). “Development and validation test of a novel Self-centering Energy-absorbing Dual Rocking Core (SEDRC) system for seismic resilience.” Engineering Structures, 211. pp. 1-14.