Hashemi, Yousef-Beiki, Darani, Clifton, Zarnani, and Quenneville (2019)
A resilient slip friction joint is designed to be embedded within the members of a frame and use frictional damping in order to supply energy dissipation and self centering to the structure. The resilient slip friction joint is tested individually under experimental load conditions, and the results were used to design a numerical 5 story model of a structure using resilient slip friction joint braces and test the system under seismic conditions.
System Concept
A resilient slip friction joint (RSFJ) employs frictional damping in order to both dissipate seismic energy and provide a self centering force on the system. This paper proposes the use of a RSFJ brace in which the RSFJ provides resistance to seismic forces and the remaining members are designed to remain elastic such that they move with the RSFJ.
The RSFJ uses frictional damping through the use of two sliding plates that move through cap plates that are held together by elastically compacted disc springs. When a force on the system exceeds the design force, the two moving plates are pulled outward, thus resulting in expansion of the cap plates due to the discs.
The RSFJ is located embedded within the members of the brace. A steel jacket can be placed around the RSFJ in order to prevent damage. Several braces can be combined to create a frame. A secondary fuse is included within the body of the RSFJ with the intention of increasing the deformation capacity of the fuse and to therefore withstand greater seismic loads. The RSFJ is designed to behave elastically until an ultimate limit state at which the clamping bolts begin to yield in tension, then elongate to provide ductile inelastic behavior after the limit state, which would allow up to twice the initial displacement demand.
Experimental Study, Results and Discussion
The RSFJ component is experimentally tested within this experiment. The behavior of the clamping bolts within this fuse is determined by manufacturing a RSFJ and loading it within an actuator. The RSFJ is erected with the cap plates and middle plates having a known ultimate strength, and 8 clamping bolts holding the plates together, rather than the initial design of 12 bolts due to a force limit on the actuator. Both the individual clamping bolts and the RSFJ fuse are tested under cyclic loading. Due to yielding and plastic deformation of the clamping bolts, which allows for the RSFJ to approach strengths sufficient for MCE events. The fuse exhibited a strength of approximately 1.25 times the design strength, which must be taken into account when designing the brace.
Following the component testing of the RSFJ, a five story steel structure using the RSFJ brace is numerically modeled and tested under seismic loading. Dead loads were applied to the model and the structure was tested using a displacement based design in order to determine the ultimate limit state that the structure could withstand. A target design drift for the frame was considered to be 2% under loads, after which the RSFJs would continue to deform, therefore allowing the structure to withstand up to a 3.75% lateral drift, and to strengthen to a 25% greater resistance to seismic loading. With the 2% lateral drift in consideration, the structure was able to withstand a 4800 kN shear force, and the 3.75% lateral drift allowed a shear force of 6000 kN. The system was therefore in agreement with the base shear, and therefore both dissipated seismic energy while maintaining high self centering capacity.
Reference
Hashemi, A., Yousef-Beiki, S.M.M., Darani, F. M., Clifton, G.C., Zarnani, P., and Quenneville, P. (2019). “Seismic performance of a damage avoidance self-centring brace with collapse prevention mechanism,” Journal of Constructional Steel Research, 155. Pp. 273-285.