ERIES-RACKSLIDE

2024 - 2025

Seismic Eng.

Dimitrios Vamvatsikos

Igor Lanese

Dimitrios Tsarpalis

Dimitrios Konstantinidis

Christoph Adam

Nicholas Kyriakides

+5 more

GEM Taxonomy string

S+SL+BOL/LFBR

2024 - 2025

Seismic Eng.

GEM Taxonomy string

S+SL+BOL/LFBR

Content sliding investigations for pallet racking systems

ERIES-RACKSLIDE

STEEL STRUCTURES

Project Report

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Dataset Description

The ERIES-RACKSLIDE project is an experimental program on industrial racks.

Specifically, two racking systems (of different height, period, and stiffness) have been tested against multi-component earthquake motion. The specimens are 1:1 scale replica of two pallet loading levels that characterize typical ARSW (Automated Rack Supported Warehouse) and APR (adjustable pallet racking) configurations. It comprises two upright frames, with bracing elements “hooked” on the uprights. The uprights are bolted via end-plates at their bottom and top to the Eucentre 9D System base table and top platform, respectively. All members are made of cold-formed steel sections. Up to three pallets of 590 kg are placed on each of the two loading levels, plus the minimal weight of the rack (<300 kg).

The program was carefully designed in order to comprehensively test the seismic response of racking systems including: (i) testing different loading levels (“story levels” in conventional building parlance), (ii) testing pallet sliding, (iii) testing the effect of CSSI (Content-Structure-Sliding Interaction), (iv) testing of the POS (plastic ovalization strategy), which refers to a concept to introduce some ductility to otherwise non-ductile racking systems (in cross-aisle direction), as well as additional low-cost mitigation measures.

The project has the following main objectives:

− 1. To assess sliding displacements on racks with different structural characteristics (finishing of contact surface, stiffness, height) and at different loading levels.

− 2. To assess the accuracy of the ED1 modification factor employed in EN16681 to account for the reduced effective mass of pallets due to sliding.

− 3. To calibrate simplified and detailed mechanical models to correctly account for CSSI.

− 4. To verify the efficiency of the POS design in providing ductility to racks and confining damage to diagonals.

− 5. To calibrate empirical relationships to assess pallet sliding for future code applications.

These objectives have been fulfilled by performing a combination of material characterization tests (with ample support from the participating manufacturers), static friction tests and shake table tests under inputs with increasing intensity. Moreover, numerical and analytical models have been realized to support testing, analysis, and design of the rack specimens and to develop reliable methodologies to account for CSSI during design and assessment.

ERIES-RACKSLIDE brings together seven universities, one association of manufacturers, and two supporting industrial partners with active interest in pallet sliding research, and proposing the implementation at the Eucentre 9D System facility to conduct innovative investigations that will form the state-of-art in content- structure-sliding interaction and inform the future of EN16681, the seismic rack-design standard.

The experimental campaign of the ERIES-RACKSLIDE project was carried out at the EUCENTRE-IUSS Research infrastructure, within the framework of ERIES project (Engineering Research Infrastructures for European Synergies). ERIES is funded by the European Commission's Horizon Europe program, it is coordinated by the Scuola Universitaria Superiore IUSS in Pavia, has a budget of €11.6 million and has a four-year duration, from 2022 to 2026. ERIES aims to provide transnational access to advanced research infrastructures in structural, seismic, wind, and geotechnical engineering. The project seeks to enhance resilience against natural hazards such as earthquakes and extreme winds by fostering innovative and sustainable solutions to mitigate economic losses and social disruptions. Additionally, it develops new technical standards and methodologies to improve infrastructure safety and supports frontier research through international collaboration.

Dynamic testing

Pallet sliding

Pallet friction

POS design

CCSI

Static friction tests

Shake-table testing

Racking systems

Specimens

1. Specimen A

Specimen A represents a single bay-and-frame of a warehouse located between load levels 12 to 14. While the geometry and unit load masses accurately represent the rack configuration at its topmost levels, the steel profiles used in the specimen correspond to those employed at its bottom part. This choice was made because the profiles at the bottom are heavier, thus ensuring that: (i) in the sliding tests, where sliding effects are the primary concern, no unintended damage develops in the steel members and (ii) in the collapse tests, where damage accumulation is of interest, the specimen uses the true steel members of the rack. This compromise is not relevant for Specimen B, since uniform steel profiles are used along the height of the structure. The rack is assumed to move almost as a rigid body with negligible interstorey drift. To ensure that the middle load level moves together with the two platforms, an external bracing system is installed, consisting of two pairs of tensioned cables.

The pallet beams of Specimen A are designed to support two pallets instead of three, thus the plan dimensions of the specimen are 2270mm × 1100mm. Accordingly, two 590kg EUR-pallets are placed on each load level, resulting in a total load of 4 × 590kg = 2,360kg.

The main setup principles adopted for Specimen A are also applied to Specimen B, with some adjustments necessary to accommodate their geometric differences.

1. Sliding and collapse tests

Identical down-aisle excitations are applied to the two tables, comprising numerous uniaxial and biaxial sliding tests, as well as three collapse protocols.

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Instrumentation

A comprehensive instrumentation system was deployed to record key response parameters during testing. The system consists of two main components: a set of sensor devices and an optical tracking system. This instrumentation remained unchanged for all tests, from the sliding series to the collapse ones.

The sensor devices set includes accelerometers, strain gauges, and displacement transducers.

2. Static friction tests

The test configuration consisted of a hydraulic jack applying horizontal load (F) to the side surface of one of the two steel beams, while its opposite end reacted against the wooden pallet. The applied force was gradually increased until measurable sliding was recorded (δ >1mm), which was interpreted as the onset of static friction and defined the corresponding friction load F_s.

Instrumentation

A displacement transducer was mounted to measure the cross-aisle relative displacement (δ) of the pallet and the second beam.

2. Specimen B

Specimen B is a 1:1 scale replica of a small portion of an entire racking system, specifically a single bay and frame corresponding to load levels 3 to 5. It comprises two upright frames, each consisting of two uprights and diagonal elements, as well as three sets of twin pallet beams hooked on the uprights. The first and second pair of beams (representing levels 3 and 4) are loaded with pallets, whereas the third pair (level 5) remains unloaded due to height limitations of the shake table system. The specimen height is 4.06m, manufactured precisely to the available height between the two attachment levels, while the plan dimensions are 2.94m × 1.10m. All structural members are made of cold-formed steel sections, with the pallet beam and upright surfaces finished with powder coating, while the diagonals are zinc-coated.

The uprights are bolted via stiff end plates at their bottom and top to the bottom table and upper table, respectively. Bottom table consists of a rigid steel platform with plan dimensions 4.80m × 4.80m and a grid of holes for M30 bolts that facilitates the attachment of the test specimen to the platform. On the other hand, upper table is a lighter structure made of aluminium truss members with usable plan dimensions ~4.67m × 3.75m. The two tables are connected by four stiff steel columns of hollow square sections, pinned at both ends so no unintended coupling is introduced, and the tables can move independently. The rack is assumed to move almost as a rigid body with negligible interstorey drift. To ensure that the middle load level (representing level 4 of the rack) moves together with the two platforms, an external bracing system is installed, consisting of two pairs of tensioned cables. These cables not only maintain synchronized movement of the load levels but also provide a more realistic representation of the high structural stiffness of the ARSW rack along the down-aisle direction due to the presence of the bracing towers.

Three standard EUR-pallets, each weighing 590kg, are placed on each of the two loaded levels, for a total load of 6 × 590kg = 3,540kg. The unit loads are represented by cast concrete blocks, which are fastened to the wooden pallets via plastic straps. To ensure realistic test conditions, used-but-undamaged pallets are selected to replicate the actual pallet-on-beam surface conditions during warehouse operation.

1. Sliding and collapse tests

Identical down-aisle excitations are applied to the two tables, comprising numerous uniaxial and biaxial sliding tests, as well as three collapse protocols.

pdf