Model Analysis of Steel Frame Structures Considering Interactions between Racks and the Frame

Abstract

The steel racks on the floor are seen as live loads in the current design process, ignoring the interaction with the supporting frames. In this paper, multiple steel racks with different masses and stiffnesses are placed on the first floor of a two-story main structure to form different real structures (RS). The corresponding simplified structures (SS) are frames with the mass of steel racks concentrated on the first floor of the main structure. Modal analysis is performed to analyze the relationship between the periods of RS and SS in the cross-aisle direction. Firstly, the beams on the first floor are assumed to be infinitely rigid. The relationship between the periods of the rack TRk, the simplified structure TSS, and the real structure TRS under different mass ratios α is established, and an accurate equation relating TRS with TRk and TSS is proposed. Moreover, by considering the influence of finite beam stiffness, the interaction between racks and the main structure is studied by constructing different analysis models. The effect of the main structure on the racks is reflected by a combined system consisting of beams and racks. A modified model, distinguished from SS by considering the effect of no-mass racks, is constructed to study the strengthening effect of the racks on the first-floor beams. The effect of the top connecting bars is also analyzed.

Keywords

• rack
• frame
• modal analysis
• period relationship
• floor beam stiffness
• interaction