Lou, Wang, Li, 2023
In this study, a new self-centring and energy-dissipating steel connection was designed with the purpose of reducing residual structural damage after earthquakes. The system also comprises replaceable properties which allow fast repair of the structure when damage occurs at energy-dissipating components of the system. The steel connection is made of pre-stressed bars connecting the frame beam and the beam-column joint while energy is dissipated by plates bolted on the interfaces of the beam joint. Specimens of the proposed system with different design parameters were subjected to quasi-static tests with a displacement-controlled loading protocol. A numerical simulation was also used to further investigate the seismic behavior of the connection. Both the experimental and numerical results were consistent, exhibiting anticipated hysteresis curves by the proposed system with small residual drift and concentrated damage at energy-dissipating plates proving itself as an effective novel seismic resilient system. The system also verified its replaceable property by providing similar results before and after switching the replaceable components.
System Concept
The proposed joint system comprises pre-stressed bar, cover plates and buckling-restrained plates in three sets of different sizes. Self-centring component is facilitated by prestressed bars and energy dissipation component is provided by attached plates at the upper and lower interfaces of the joint. The cover plate includes a reduced section designed which controls the bending and buckling behavior. Damage is ensured at the plates while the self-centring components of the system and the rest of the structure remain elastic. When subjected to lateral load, the prestressed bars begin to open as the frame beam in the middle of the flange rotates. This causes the buckling restrained plates to deform, thus dissipating energy. Removing the load would close the gap as the prestressed bars relax, recentering the system. The system was also designed for easy removal and replacement which can be carried out by hand by removing and re-tightening the bolts.
Experimental Study, Results and Discussion
Three specimen sets each comprising different widths of the restrained segments were tested under displacement-controlled quasi-static cyclic loading protocol: 50, 70, and 120 mm. A compressive load of 5321 kN with an axial ratio of 0.05 was applied. A 200 ton capacity jack was used for axial compression load while two 50 ton actuators were placed at the sides to exert loads in opposite directions to the specimen. Numerical simulation was also performed to validate the experimental results using a finite element analysis method.
Compared to the joints without the proposed plates that exhibited linear response, the proposed joint system demonstrated good seismic performance such as by generating hysteresis curves. Pinching effect, however, occurred at the large set as a result of the bolt slip. Envelope curves were also assessed showing stiffness was maintained initially by the beam and column followed by the prestressed bars and energy dissipating plates. When subjected to cyclic loading, a gap at the joint increased gradually with the drift ratio after it reached 1.5%. As anticipated, damage was concentrated at the energy-dissipated plates preventing permanent damage at other components. The responses from simulations were identical with the experimental observations verifying its high seismic performance with controlled drift ratio of less than 0.5% in all specimens.
Reference
Lou, T., Wang, W., & Li, J. (2023). Seismic behaviour of a self-centring steel connection with replaceable energy-dissipation components. Engineering Structures, 274, 115204.