PSI - Issue 70

Umeshkumar T. Mourya et al. / Procedia Structural Integrity 70 (2025) 35–42

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connection. A typical upright profile and end-connector with connection is shown in Fig. 1. The tabs in the end connector are not in perfect contact with the perforation edges in the upright due to the oversized perforations. This introduces inherent looseness in the beam-to-upright connections. The looseness contributes to the non-linear behaviour of the connection and also introduces pinching in the cyclic response of such connections (Bernuzzi and Castiglioni, 2001; Jovanović et al., 2019) . It is, thus, important to quantify the looseness in such connections to ascertain its impact on the behaviour of the frames. The European standard EN15512 (2020) and American standard RMI (2019) recommend bending tests to ascertain the looseness in the connections. The moment-rotation behaviour has been extensively studied in literature (Markazi et al., 1997; Prabha et al., 2010; Zhao et al., 2014; Mohan et al., 2015; Gusella et al., 2018; Shah et al., 2016; Mourya and Jayachandran, 2024; and many others), however the experimental studies on the looseness of the connection is very limited (Dumbrava and Cerbu, 2022). An experimental study has been presented in this paper on the quantification of looseness in the rack connections.

Fig. 2 shows a typical response of a connection when subjected to reversal of loading. As there is no rigid connection between the end-connector and the upright, there exists gaps between the edges of the upright perforations and the tabs. When the load is applied the end-connectors rotate with the lateral movement of the tabs till the edges of tab and upright come in contact. During this phase, there is rigid body movement of the end-connector which results in a slip in the connection without the connection experiencing any load. When the connection is unloaded and loaded in the reverse direction, the direction of rotation and slip reverses as shown in Fig. 2. The half of the total slip is defined as looseness in the connection (EN15512, 2020). Fig. 1. Typical beam-to-upright connection in a storage rack

Fig. 2. Definition of looseness per EN 15512 (2020)