Xin Yan, M Shahria Alam, Ganping Shu, Ying Qin, 2023
A self-centering, viscous damper (SCVD) is proposed to have the ability to improve seismic resilience of structures by offering high flexibility in load resistance, deformability, energy dissipation. The proposed SCVD comprises of a viscous energy dissipation system and a disc spring system that provides self-centering system capabilities. A fabrication process of the SCVD was additionally proposed, along with pre-compression procedure to assemble the damper for testing. Both systems were tested individually through a series of tests and then tested as an integral damper to investigate peak deformation, residual deformation, and peak floor acceleration. The effectiveness of using the SCVD as bracing elements in structures to control seismic activity was also investigated and compared to buckling restrained and self-centering braced frames.
System Concept
The SCVD consists of two systems: a viscous energy dissipation system and a disc spring self-centering system. The viscous energy dissipation system includes a viscous damping cylinder filled with silicone oil and a piston fixed on a piston rod. The size and configuration of the openning of the piston controls the desired viscous damping force. The disc spring self-centering system is connected to the energy dissipation system on both sides with a threaded junction and includes two bearing plates, disc spring cylinder, and 22 preloaded disc springs in series that increase deformation capacity. The bearing plates and disc springs are constrained by screw sleeves along the piston rod, and therefore movement results in compression of the springs. Additionally, a fabrication and pre-compression process is suggested for the new proposed SCVD. A specifically designed workstation and reaction frame are used to assemble and preload the systems, in which axial load is transferred from a hydraulic jack to the bearing plates. Both systems work in parallel with the piston rod to convert input energy into thermal energy for dissipation. The piston ride returns to initial equilibrium with the support of the self-centering system.
Experimental Study, Results, and Discussion
Initially, the disc springs connected in series were tested in compression and displayed a proportional relationship between restoring force and increasing loading displacement. While disc springs displayed relatively low capacity for energy dissipation, a residual deformation of nearly zero indicated an adequate self-centering capability with a bearing capacity of 378 kN and maximum deformation of approximately 83.6mm. The SCVD were tested using displacement gauges, installed at the ends of the damper to measure the displacement of the piston rod, to determine the actual loading displacement of the damper. Strain gauges were used to ensure that all compoents remained elastic during the test. Tests were performed in three stages: testing of the self-centering system, viscous energy dissipation system, and with both systems. Cyclic loading tests were performed on the self-centering system to ensure the feasibility of applying preload, while the energy-dissipation system was tested to measure the maximum internal friction. In the third stage, both systems were assembled into an integral damper and tested to investigate the effects of initial preload on loading frequency, along with the effect of loading amplitude on the performance of dampers. The SCVD was tested under dynamic load conditions and loading frequency where results indicated that the viscous energy dissipation system is a velocity -dependent device with relatively good energy dissipation capacity. The damper also displayed great performance in compression and tension. A majority of deformation was pronounced in the disc springs, while other parts of the system were negligibly stressed. A maximum viscous damping of approximately 38% was attained when tested at high frequency.
Reference
Xin Yan, M Shahria Alam, Ganping Shu, Ying Qin; (2023). “A novel self-centering viscous damper for improving seismic resilience: Its development, experimentation, and system response.” Engineering Structures