Fortney, Shahrooz, and Rassati 2007

The authors conduct large-scale cyclic tests on a coupling beam between core walls with a replaceable element at the midspan of the beam. Coupling beams are intended to form hinges prior to hinges at the base of wall piers. This study attempts to form these hinges in specific, easily replaceable identifiable and replaceable zones.

System Concept

The goal of this experiment is the concentrate yielding in a specific, replaceable region. The midspan of the coupling beam (already set to form hinges prior to the base of wall piers) is ideal because it is often much more easily accessed than other parts of a structure. The fuse at the center of the beam is the same section as the main portion of the coupling beam, but with a thinner web, so as to induce yielding in a specific location.


Experimental Study, Results, and Discussion

Coupling beams are embedded in wall piers. The main section is connected to the fuse section through a slip critical connection with web and flange splice connections. Test specimens were loaded with increasing amplitude in a reverse cyclic fashion. Tests were performed on specimens with the fuse section at 50% and 70% of the shear capacity of the main section of the coupling beam. These tests were compared to those of a steel coupling beam without the fuse element at its midspan.

In the traditional steel couple beam, little damage was observed in the piers, indicating a sufficiently ductile connection to the wall piers. The steel coupling beam with a fuse element at the midspan experienced early energy dissipation and low stiffness. Weld fractures also occurred after the beam reached 5% chord rotation.

The authors recommend that the fuse be designed for the ultimate shear forces so that it can withstand expected shear forces, and that the rest of the coupling beam be designed as a larger member.


Reference

Fortney, P. J., Shahrooz, B. M., and Rassati G. A. (2007). "Large-Scale Testing of a Replaceable “Fuse” Steel Coupling Beam," Journal of Structural Engineering, 133.12, pp. 1801-1807.