Plate-type steel fuse for enhancing the seismic performance of steel storage rack structures

Past earthquakes have shown that steel storage rack structures are significantly vulnerable due to their specific structural characteristics, which is primarily governed by hook-type beam-to-upright joints. As adding devices or structural elements can obstruct storage bays and limit access, seismic retrofit of these structures is challenging. This study proposes a damping device which consists of a steel plate with two fuse notches and can be attached to beam-to-upright connections without affecting the structure's functionality. In addition to enhancing structural integrity and stiffness, this plate-type fuse dissipates seismic energy through controlled in-plane yielding when subjected to joint rotations. The mechanical behavior of the fuse is theoretically derived and verified using finite element analyses. To this end, an experimental rack subassembly test under cyclic loads is modeled and validated in both Ansys and OpenSees. Subsequently, it is retrofitted with the proposed fuse and its hysteretic behavior and the accuracy of the derived theoretical formulations are evaluated in a comprehensive parametric study. To further investigate the effectiveness of the developed damping device, a benchmark three-story four-bay rack structure is modeled and retrofitted in OpenSees. The seismic performance of this structure is evaluated and compared before and after retrofit using nonlinear time history analysis under a suite of ground motion records and pushover analysis. The results show that the original structure experiences global failure and dynamic instability under the Maximum Considered Earthquake hazard level, whereas the retrofitted structure meets the Collapse Prevention performance objective as designed using the established theoretical formulations.