Research On New Type Removable Beam-Upright Connections Of High Ductility In Storage Structures Under Low-Cycle Reversed Loading

Assembled steel storage racks are widely used in various industries as the mainstream storage structures at present. The speedlock connections of the storage racks have poor performance in loading capacity and energy consumption, which lead to weak seismic capacity and security risks. It has important theoretical significance and application value to improve the traditional speedlock connections and research the performance of new type beam-upright connections.The new type removable beam-upright connections of high ductility are proposed on the basis of speedlock connections. The new connections combine the advantages of speedlock and bolted connections, which can promote the introduction of full-galvanized storage racks. The processing technology of new connections abolishes the traditional coating process to rust protection, which can lead to non-pollution and high-efficient production of assembled steel storage racks, and an impressive promotion of the structural performance and sustainable development.There are five modes of beam-upright connections researched in this paper. Firstly, according to rack specification, the corresponding specimens and the double-cantilever beam test device are designed to research the five types of connections for cycle loading. Secondly, the loading capacity and seismic behavior of the connections are analyzed with experimental results and phenomenon. Then comparing with the experimental results, the connections are numerical simulated through the finite element software to summarize the impact factors in the structures. At last, the different impact factors are researched with the parameterization analysis to provide reference in engineering application and further improvement.Through comparative analysis, several main conclusions are obtained as follows:1. The failure mode of the disconnect type connections varies due to the addition of the perforation bolts through the uprights. The failure mode of the speedlock connections is initiated with yielding of the upside and downside hooks in a progressive sequence towards the beam neutral axis for monotonic loading. The perforation bolts through the uprights makes the failure mode develop the cracks in the upper end of the beam where stress concentrated.2. The failure mode of the integral type connections mainly occurs in the combinations of beams and corbels, due to the different connection forms. The new connections fail with the falling off of the bolts at the end of the beam. The connections with the perforation bolt through the beams fail in the bolt fracture. The connections with the riveted nuts fail in the falling off of the riveted nuts at the end of the beam.3. The hysteretic curves of the five connections based on low cyclic reversed loading show different degrees of reduced pinch phenomena, which reflect some degree of slippage and looseness. The addition of the perforation bolts through the uprights narrows the gap under positive and reverse loading, which improves the loading and seismic capacity of the connections.4. The integral beam end connectors realize the integrity of the beam-upright connections, which improve the loading, ductility and energy dissipation capacity of the connections. It makes a critical difference to improve the seismic performance of the new type connections.5. The connection type combining beams and corbels has an important influence on loading capacity and seismic behavior of the new type connections. Opening screw holes in the end of the beams and then connecting through the four bolts, which has the best performance in the loading and seismic capacity of the new type connections.