Seismic retrofit and protection of steel storage rack structures using a metallic damper
Mohammad Mahdi Javidan,Sajid Hussain,Seunghee Park,Jinkoo Kim
Abstract
The seismic performance of rack storage structures is mainly governed by the beam-to-upright connections, which are highly flexible and show considerable stiffness and strength degradation, along with pinching behavior. To address these vulnerabilities, a steel hysteretic damper is proposed which can be installed at these joints to improve seismic performance and energy dissipation. The damper consists of an L-shaped steel plate with a tapered section which acts as a fuse, yielding under rotational deformation at the joint. The mechanical behavior of the damper is theoretically formulated for the design purpose and it incorporates the derivation of slope-deflection equations for tapered members. The accuracy of the formulation is verified by comparing its prediction with a detailed finite element model in Ansys and OpenSees. The effects of geometric imperfections and buckling is also investigated using a probabilistic approach and finite element simulations. To further investigate the effectiveness of the proposed device, an experimental test on a beam-to-upright connection from a rack subassembly subjected to cyclic loading is simulated and validated in OpenSees. The damper's model is then applied to the validated system, and the cyclic behavior before and after retrofit is compared in terms of hysteretic response and energy dissipation. Results show that the proposed energy dissipation device can enhance stiffness, capacity and energy dissipation capability of the joints. The theoretical formulation, analysis modeling approach and simulations presented in this study provide a detailed insight into seismic behavior of steel rack storage structures.
