Study of seismic control systems on the behaviour of industrial storage racks
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Steel storage racks are structures which are used in factories and warehouses to store goods and merchandises. They consist of uprights, beams and braces made of cold-formed steel, and although they are very light in comparison with conventional structures, they are designed to carry very heavy loads. Storage racks are designed to resist horizontal loads in orthogonal directions using two different frame systems: moment resisting frames in down aisle direction and braced frames in cross aisle direction. The design of racks is different from typical buildings because they are made of slender thin walled members, hence, making them sensitive to global, local, and distortional buckling if overloaded. Moreover; the connections demonstrate highly nonlinear behaviours under loading. Due to the aforementioned reasons, the design of racks poses major challenges for engineers especially in seismic regions where mitigating the vulnerability of racks is important. The objective of this numerical and experimental research was to investigate the seismic behaviour of storage racks and to establish the effectiveness of two alternative control systems to improve the performance of the racks under seismic loads. The control systems studied are new generation passive dampers: (i) a pounding tuned mass damper (PTMD) and (ii) a base isolation system. Full scaled shake table testing was performed at the University of Technology, Sydney (UTS) to study the dynamic behaviour of storage racks and to verify the numerical models. As part of the research, numerical models based on the Finite Element Method (FEM) were developed and applied to conduct parametric analyses of the racks in order to compare the seismic response of cross aisle braced frames of different heights with and without control devices. The FEM results showed that PTMD dampers enhance by up to 40% the seismic behaviour of racks under 5 meters height while the base isolation system was more effective for tall racks. Financial support for this research was provided by Dexion.
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