CAST CONNEX® Scorpion™ Yielding Connectors are modular, replaceable, standardized hysteretic fuses that provide enhanced ductility and improved performance in the retrofit of seismically deficient structures or for use in the Seismic Force Resisting System of new structures.
Each Scorpion Yielding Connector (SYC) consists of specially designed cast steel and fabricated elements which connect to and transmit forces between connected elements. The SYC is intended to remain elastic during ordinary building service loading and provides energy dissipation during a sizable earthquake through the cyclic inelastic flexural deformation of the SYC’s cast steel yielding fingers. The system exhibits a full, symmetric hysteresis characterized by an increase in stiffness at brace elongations greater than the design level. This increase in stiffness is a result of the second-order change in geometry of the yielding fingers, each of which is shaped to promote the spread of plasticity along its entire length.
- As SYC devices are standardized, the cost and delay associated with additional project-specific testing is typically eliminated.
- SYCs exhibit a stable and reliable post-yield stiffness which increases at large deformations. This behavior results in a better distribution of yielding over a building’s height and decreases the likelihood of the formation of a “soft story,” which is a significant concern with bracing elements that provide little or no post-yield stiffness like traditional Buckling Restrained Braces and friction damping systems.
- Due to the high elastic stiffness of the SYC devices, the brace member selected by the engineer of record has a significant contribution to the elastic stiffness of the assembly. This uncouples the elastic stiffness from the yield load of the brace. With SYCs, engineers can design the system to have a low yield force and a high elastic stiffness, thereby minimizing expected story drifts while simultaneously reducing the seismic forces that develop in the lateral force resisting system during a design-level earthquake.
- Unlike traditional Buckling Restrained Braces where the core of the brace is not accessible, the yielding fingers of the SYC device can be inspected for signs of significant damage after an earthquake event, offering building owners a way to gauge whether replacement of the brace is necessary. SYC devices can also be more readily replaced following a sizable earthquake.
- Because all inelastic behavior is confined within the SYCs, engineers are provided with the flexibility to use the devices in several structural configurations, including a single bay, single storey X configuration – a configuration that reduces the number of frames which are obstructed by the lateral force resisting system and, in the case of retrofit, can reduce the costs of replacing building envelope and finishes after installation.
- SYCs dissipate seismic energy through yielding of specially designed, triangular shaped steel yielding fingers. Unlike friction damping systems, the long-term behaviour of a hysteretic yielding system is well understood and the seismic properties of the device are not dependant on the long-term characteristics of normal force generating elements or frictional surfaces.