Calado, Proenca, Espinha, and Castigloni 2013
A proposed steel fuse is studied in a composite beam to column subassembly under cyclic and monotonic loading. It was found that the fuse concentrates plastic deformation and energy dissipation into a repairable component of the system, therefore decreasing repairability time and costs after an earthquake.
System Concept
The steel fuse in this system was proposed in an earlier study. The fuse features steel plates bolted to the web and bottom flange of the beam and embedded within the beam. The steel fuse is proposed to have high ductility and yield prior to the surrounding concrete, therefore dissipating seismic energy and preventing failure of the irreplaceable beams and columns. As a result, the fuse is connected through bolted connections such that it is easily replaceable.
The surrounding composite beam and column system consists of a composite beam and a reinforced concrete slab with the fuse located at the connections. The steel fuse is embedded within the concrete slab in order to prevent the two surrounding layers of concrete from colliding or from yielding under loading. As a result, the columns and beams were designed with a higher cross sectional area in order to limit the stress applied to the irreplaceable components and to concentrate plastic deformation at the ductile and replaceable fuse.
Experimental Study, Results, and Discussion
Three subassemblies of the beam to column connections were produced with different effective lengths of 140, 170, and 200 mm. The subassemblies are each tested with four different fuses. The fuses are designed to have different geometries of flange plates, but all have the same web plate area since the web plate is designed to be resistant to plastic deformation. The fuses were tested for repairability by testing each specimen two times with each fuse under cyclic loading, therefore testing each subassembly eight times, until failure of the fuse system.
A load cell was located at the top of the beam in order to apply a moment to the fuse located at the bottom of the beam. 21 displacement transductors were located incrementally across the beam and measured the top displacement of the subassembly. The loading followed an ECCS protocol and was informed by loading independently of the yield displacement.
It was found that the fuses acted to prevent plastic deformation at the irreplaceable components of the subassembly by absorbing seismic energy due to their high yield point. The fuses also proved to be easily manufactured for mass production and replaceable to limit repair time and costs. It was also found that fuses with higher capacity ratios of moment developed by the fuse to moment developed by the beam were more effective in providing plastic deformation and dissipating seismic loads, and that capacity ratio was the most impactful design parameter, though a high capacity ratio could also lead to plastic deformation of the beams, which can be avoided with an upper bound. Overall, the fuse exhibited stable hysteretic behavior under loading and facilitated repairability and energy dissipation of the system.
Reference
Calado, L., Proenca, J.M., Espinha, M., and Castigloni, C.A. (2013). “Hysteretic behaviour of dissipative bolted fuses for earthquake resistant steel frames,” Journal of Constructional Steel Research, 85. pp. 151-162.