Bruneau 2007
In traditional structural systems, ductile behavior has been achieved by the stable plastic deformation of structural members. However, in recent decades, the idea that energy dissipation should occur in the disposable elements has gained steam. These elements are called structural fuses, and a main feature that makes them desirable, is that they can be replaced without causing a disturbance to the rest of the system. Hysteretic energy dissipation should occur in disposable and replaceable structural elements. This paper reviews emerging hysteretic systems. The authors asses various fuse systems and their advantages over conventional structural configurations. The emerging hysteretic systems explained in this paper are SPSWs, buckling-restrained braced frames, and rocking braced frames.
Steel Plate Shear Walls
SPSWs are designed to rely on the development of diagonal tension yielding for seismic energy dissipation. Light-gauge cold-rolled and low yield strength steel was used for the infill panel. Reduced beam sections at the ends of the horizontal boundary members were used. This was intended to reduce the overall system demand on the vertical boundary members. By using simple models, an experimental program was developed in order to investigate how to replace a steel panel after a severe earthquake, as well as how a repaired SPSW will behave in a second earthquake. The specimens used before and after replacement showed the same behavior.
Buckling Restrained Braced Frames
Buckling-restrained braces consist of a ductile steel core inside to yield during tension and compression. The steel core is placed inside a steel casing, and casing is filled with mortar or concrete. Unbonded material is wrapped around the steel core to eliminate transfer of axial force from steel core to mortar. This combination prevents the core from buckling as it yields – hence the name: buckling-restrained brace.
Many uniaxial tests have been conducted on BRBs to show that they exhibit stable hysteresis behavior and a long cycle fatigue life. In order to develop a design procedure, a 3-story frame was designed and investigated. This experimental project also assessed the replaceability of BRBs. Another purpose of the experiments was to examine seismic isolation devices intended to protect non-structural components from severe vibrations. In order to show this, a bearing with a spherical ball rolling in conical steel plate (BNC) seismic isolation devices was used. The BNC was installed on the top floor of a frame model, and its acceleration and displacement were recorded.
Rocking Braced Frames
It is desirable to design structures able to deform inelastically and constrain the damage to easily replaced ductile fuses to produce stable hysteretic behavior of the structure. In one example, failure or release of the anchorage connections allows a steel truss pier to rock on its foundation. Additional PED devices at the uplift location could control the rocking response while providing energy dissipation. This system was also able to provide an inherent restoring force capability which allowed for automatic re-centering of the tower.
Reference
Bruneau, M. (2007). “Emerging Hysteretic-Based Seismic Systems: Convergence of Ideas in Ductile Steel Design,” Proceedings of the 10th World Conference on Seismic Isolation, Energy Dissipation and Active Vibrations Control of Structures, Istanbul, Turkey, May 28-31.