Shahrooz, Fortney, and Harries 2018
In order to make the repair and replacement of steel coupling beam systems cheaper and more efficient, a replaceable fuse was fixed at the midspan of the steel coupling beam in order to absorb the inelastic deformation resulting from energy dissipation into a more easily replaceable component of the system. It was found that the fuse was replaceable, and that it successfully absorbed most of the energy resulting from ground motion.
System Concept
As a basis for this work, a prior model of a steel coupling beam was used, in which a steel beam was fixed with endplates spanning between two concrete walls, this paper fixed a fuse at the midspan of the coupling beam in order to concentrate the energy dissipation capacity into a more easily replaceable component of the system. The fuse was designed such that it would reach its inelastic deformation capacity prior to the beams reaching deformation capacity under design ground conditions in order to prevent damage to other components of the system and to prevent specimen failure under maximum considered earthquake conditions.
Experimental Study, Results, and Discussion
The experiment consisted of a half scale 20 story office prototype building representing a single coupling beam from the fourth story. The specimen utilized a two pier wall segment with a coupling beam featuring a midspan fuse. Two fuses were tested. In the first test, one wall was moved vertically, while the other remained static. The test subject was then loaded to a chord rotation within the coupling beam of 2% in order to mimic the design ground conditions. Then, a new midspan fuse could be installed.
The new fuse with the same embedded beam system was then subjected to a maximum chord rotation of 14%, which is 5 times greater than the conditions under the maximum considered earthquake (MCE). It was shown that the fuse could behave to its intended capacity of 590 kN. The hysteretic responses within the two tests were also similar, which indicates that the fuse can be replaced with little effect on the system. The results from this study were compared to a previous study in which no fuse was used, which had similar results except that the steel beam with no fuse had a higher post yield stiffness.
The fuse reached its expected shear capacity prior to deformation of the embedded beams, and there was minimal damage to the walls. The normalized shear in the embedded beams was also less than the capacity, meaning that the fuses were the primary source of energy dissipation.
Reference
Shahrooz, B., Fortney, P.J., and Harries, K.A. (2018). “Steel Coupling Beams with a Replaceable Fuse,” Journal of Structural Engineering, 144. 2, pp. 29.