PSI - Issue 44

Marius Pinkawa et al. / Procedia Structural Integrity 44 (2023) 2342–2349 Marius Pinkawa, Cristian Vulcu, Benno Hoffmeister / Structural Integrity Procedia 00 (2022) 000–000

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1. Introduction and motivation Automated Rack Supported Warehouses (ARSW) gain rising interest due to the growing market of e-commerce. Large and efficient storage capabilities are essential to cope with the huge amount of merchandise which is handled nowadays. In this regard, ARSW structures provide an ideal solution regarding cost savings, optimal space utilization, and energy consumption. Because there is a lack of guidelines and design codes tailored to rack supported warehouses (especially for seismic design purposes) – structural engineers refer to seismic design codes for buildings (e.g. EN 1998-1 (2004)) as well as conventional racks (e.g. EN 16681 (2016)). However, it is questionable if these codes are directly applicable to the special typology of rack-supported warehouses. Missing guidance with concrete specifications for this type of structure leads to a large diversity in the seismic design philosophies and approaches applied by the various manufacturers. In the scope of the STEELWAR project (“Advanced structural solutions for automated STEELrack supported WARehouses” – Salvatore et al., 2017-2022) current seismic design approaches as applied in practice have been assessed. Therefore, the five rack manufacturers participating in the STEELWAR project were asked to design a double-depth automated steel rack supported warehouse for low seismicity conditions, employing their typical design approach and their manufacturer-specific structural members. The resulting case studies were then modelled independently by the university members of the project consortium, according to the received technical drawings and specifications. Further on, dynamic time history analyses have been conducted to assess the seismic performance of the case studies. The different seismic design approaches were compared by means of identified failure mechanisms. Potential failure modes were ordered by utilization ratios to obtain a hierarchy of criticalities. In this way, recommendations for an optimized seismic design prioritizing the most critical failure modes could be formulated. 2. Seismic performance evaluation of double-depth ARSWs in low seismicity regions 2.1. Case study structures In total five rack manufacturers, which participated in the STEELWAR project (Salvatore et al., 2017-2022), designed a double-depth ARSWs for low seismicity conditions, employing their typical design procedures and their individual structural members. According to a non-disclosure agreement signed in the framework of the STEELWAR project, various details cannot be presented as part of the current paper. These details include among others the geometry of the structures, the cross-section and/or shape of the structural members (beams, uprights, braces, etc.), and experimental test data characterizing the strength and stiffness properties of single members. In the following, the five case studies will be labeled as CS-1, CS-2, CS-3, CS-4, and CS-5. Based on identical input parameters and boundary conditions, each of the rack manufactures designed an ARSW structure. Technical drawings and specifications of the case studies were handed over to the university related partners conducting the seismic assessment. According to the provided information, the structures were then modelled by the university partners within their preferred software. The numerical models were verified by means of modal analysis, so that the dynamic properties matched that one from the numerical models of the manufacturers. The 3D structures could basically be considered separately in their both axes – cross-aisle (CA) and down-aisle (DA) directions. Moreover, because analyses of the full 3D structure are computationally extremely expensive, mainly plain frames were analysed for the seismic assessment. Where needed, partial 3D frames were investigated. The five analysed double depth frames in cross-aisle (CA) direction are illustrated in Fig. 1. The down-aisle (DA) direction is not considered within this paper. As can be observed, the global typology of the five frame configurations in the CA direction is similar, with differences corresponding to the braces and detailing (see Fig. 1). The cross-sections of the elements and a detail of the column base are schematically sketched in Fig. 2.