Background: Limiting residual drift is one of the objectives in the design of modern structures, as small residual drifts facilitate structural repairability following an earthquake. Nitinol shape memory alloy is an advanced and expensive self-centering material capable of recovering residual deformations. On the other hand, steel slit dampers are among the desirable types of energy dissipation devices. In this study, a steel moment-resisting connection equipped with a hybrid system comprising a steel slit damper and a Nitinol shape memory alloy component is numerically investigated, and the combined performance of the energy-dissipating and self-centering components is evaluated.
Methods: First, an experimentally tested connection equipped with a slit damper is considered as the reference specimen. Subsequently, a parallel configuration consisting of a steel damping component and a Nitinol self-centering component is introduced and numerically investigated. Due to the high cost of Nitinol in practical applications, thin Nitinol wires are employed, while a series configuration of the two components is not feasible because of its higher Nitinol material demand. In designing the numerical specimens, the stiffness of the experimental reference specimen is maintained as a constant reference stiffness for the hybrid slit damper–self-centering system. 24 finite element models are developed, and the yield rotation, yield moment, residual rotation, stresses in the connection components under cyclic loading, and dissipated energy are evaluated.
Results: The results indicate that the parallel arrangement significantly increases connection strength, while increasing the contribution of Nitinol causes the hysteretic response to become progressively more flag-shaped. However, the self-centering effect in reducing residual drift remains limited. Even in the specimen containing the largest amount of Nitinol, the reduction in residual rotation is approximately 15%. The results also demonstrate that a stiffener in the connection seat region is essential to maintain connection rigidity.
Conclusion: Overall, the parallel configuration is suitable for increasing connection strength and providing limited self-centering capability; however, it is insufficient for achieving a substantial reduction in residual drift. When residual drift reduction is the primary objective, alternative arrangements, including series configurations, should be investigated considering the required amount of Nitinol, constructability, and cost.