Seismic Behaviour of Steel Storage Pallet Racking Systems - Part 2

12/05/2015 5056

Il progetto EU-RFCS "SEISRACKS2":"Seismic Behaviour of Steel Storage Pallet Racking Systems"


Carlo A. Castiglioni, Alper Kanyilmaz , Alberto Drei, Politecnico di Milano, Department of Architecture, Building and Construction, Milano, Italy
Hervè Degee, Catherine Braham, University of Liege, Department Argenco, Liege, Belgium
Benno Hoffmeister, Cristoph Heinemeyer, RWTII Aachen, Department of Steel Construction, Aachen, Germany
Ioannis Vayas, Kostantinos Adamakos, NTU Athens, Department of Steel Construction, Athens, Greece

Questa Memoria è tratta dagli Atti del XXIV CONGRESSO CTA, Torino 30 settembre - 2 ottobre 2013

Questo lavoro intende illustrare il progetto Europeo SEISRACKS2 : "Seismic Behaviour of Steel Storage Pallet Racking Systems", RFSR-CT-2011-00031. Dopo un inquadramento generale della ricerca, si presentano le attività svolte nei primi 18 mesi.
La presentazione è organizzata in tre parti: la prima fornisce un inquadramento generale del progetto ed un'identificazione delle lacune della attuale versione della norma FEM 10.2.08, nonché un inquadramento dei casi studio. La seconda parte riassume i risultati sperimentali sin qui ottenuti (WP 2, 3 e 4), e la terza descrive le attività numeriche (WP 5 e 7).

1.1 Tests on beam-to-upright connections
1.1.1 Tests in down aisle direction

Tests were performed aimed to the assessment of the moment rotation characteristic of the beam to upright connections as well as of the influence of loading conditions.
The setup of the down aisle tests is different from the one proposed in EN 15512 (2009) for beam end connector tests, and was developed within the scope of this research project to provide information about the plastic deformation capacity under realistic support and loading conditions.
The test setup represents one shelf of a rack system with a bay width of 2.70 m, commonly used for storage of 3 pallets. The height of the frame is 1.00 m and the beams are installed at half height. To load the rack with pallets two frames - a front and a back frame - are needed. The front frame is made of the rack parts (uprights and beams) to be tested. The uprights are perfectly hinged at the supports and at the top so that the sway of the frame is constrained by the beam to upright connectors only. The back frame is a kinematic frame made of hollow sections with the beam perfectly hinged to the columns (Figure 1).

The applied force F applied was imposed by an hydraulic jack. Along with the applied force the reaction forces at the supports of the front frame, the sway of the frame and the rotation of the beam ends were measured during the tests (Figure 2). The payload was applied by loaded pallets, as in a realistic loading situation. Influence of loading on the connector behaviour is investigated by testing the racks with different pay load (0%, 50% and 100% of service load).
For each load case and for each producer (4 producers) one monotonic and one cyclic test were performed. Under deformation controlled conditions by means of monotonic push over tests a load deformation curve was generated to derive the control values for the cyclic tests. The cyclic tests were also deformation controlled where the applied deformation amplitudes were related to the reference deformation ey from the monotonic tests in accordance to the ECCS cyclic testing procedure. One cycle with the amplitude factor 0.25, 0.50, 0.75 and 1.0 and 3 cycles with the amplitude factor 2, 3, 4, .. were carried out until failure. Tests results provided information related to Failure modes, Influence of payload, Differences between cyclic and monotonic behaviour, Moment rotation characteristic, Compatibility of these test results with those derived from EN 15512 standard tests, Effectiveness of safety bolts.

1.1.2 Tests in cross aisle direction
Tests are carried out for the assessment of the moment rotation characteristic of the beam to upright connectors and of the influence of pallet loads on the cross aisle deformation behaviour of the beams. It is expected that the influence of pallet loads is mainly governed by the friction between pallet and beam and the stiffness of the pallet. The influence of shear forces transferred from the beams on the behaviour of the beam to upright connection is expected to be low or negligible.
In addition to the test program initially included in the proposal, frictions tests have been performed to allow determining the influence of pallets on the cross aisle deflection resistance. The friction tests were not performed in accordance with FEM-rules (FEM 10.2.08, 2010) where the pallet beams are inclined until sliding of the pallet. In the tests performed here the beams remain in horizontal position while the pallet is moved by a measured external force. This test setup allows for the distinction of adhesive and slidin friction (Figure 3).