Qu, Liu, Hou, and Qiu 2018
This paper proposed and tested a new form of Buckling- Restrained Brace (BRB) using a steel angle fuse to be used to dissipate seismic energy in buildings and to assess post-earthquake damage. The proposed buckling- restraining elements can be reused after deformation of the fuse, as the fuse can be easily replaced after absorbing hysteretic energy to reduce interstory drift after an earthquake.
System Concept
This paper proposes a Buckling- Restrained Brace that is equipped with a steel angle fuse. The three components of the BRB include an inner and outer buckling- restrained mechanism (BRM) and a buckling- restraining angle fuse. The fuse was created using two segments of small cross sectional areas that yield in order to dissipate seismic energy, which are connected by a non yielding segment of a larger cross sectional area. The goal of the BRB is to create a replaceable system that will yield in order to dissipate seismic energy in the event of an earthquake without causing damage to other components of the structure.
Experimental Study, Results, and Discussion
The study in this paper included seven test subjects featuring specimens each equipped with BRBs numbered B0-B6. The inner and outer BRMs made of Q235 steel were reused in each of the specimens because of their replaceable nature, but the test subjects varied in geometries of angle fuses, fuse material, and debonding agent. Specimen B0 was tested as a pilot specimen and did not have any debonding agent or a non-yielding element in the fuse. The specimens were each fixed to the floor on one end, and the other end was attached to an actuator and a load cell.
The actuator applied cyclical forces to each of the specimens in the longitudinal direction. The displacements that were applied by the actuator were meant to strain the fuse in specific angles in order to measure the effects. Axial forces were measured using the load cell, while axial deformation was measured using displacement transductors.
Specimen B0 did not experience global buckling, but it did experience strength degradation at a nominal fuse strain of 3.3%, and three of the four angle fuses had ruptured, after which an adaptor and non yielding fuse element were added to the design to prevent future fuse ruptures. All other specimens exhibited similar hysteretic responses and slip deformations in the connections between the fuses and the BRMs, which increased hysteretic force diffusion by up to 15%, but did not experience any global buckling. It was concluded that the BRBs proposed within this experiment had a similar hysteretic response to previous BRBs, but that the fuses were replaceable and the BRMs were reusable.
Reference
Qi, B., Liu, X., Hou, H., and Qiu, C. (2018). “Testing of Buckling-Restrained Braces with Replaceable Steel Angle Fuses,” Journal of Structural Engineering, 144. 3, pp 10.