Steel storage pallet racks are free-standing industrial structures used to store goods on pallets across multiple levels. They are among the most common structural systems in use today, found in warehouses, distribution centres, and logistics hubs throughout Europe and the world.
Structural Characteristics
Typical rack systems consist of cold-formed steel uprights connected by horizontal and diagonal bracings to form upright frames, which are then linked by horizontal beams at each storage level. The beam-to-upright connections are typically semi-rigid, relying on clip or tab connectors that allow rapid assembly and reconfiguration — but which also exhibit complex nonlinear behaviour under lateral loading.
Rack heights commonly range from 5 to 12 metres or more, and individual bays can carry loads of several tonnes. The combination of height, slenderness, and the presence of heavy and shifting loads makes these structures sensitive to dynamic excitation.
Seismic Vulnerability
The seismic behaviour of rack structures differs fundamentally from that of conventional buildings. Key factors that contribute to their vulnerability include:
- Semi-rigid, low-ductility connections: beam-to-upright clip connectors can lose engagement or fail under repeated cycling.
- Pallet interaction: stored goods can slide, rock, or fall off beams during shaking, significantly altering the dynamic response.
- Asymmetric loading: partially loaded or unevenly loaded racks exhibit behaviour that is difficult to predict with simplified models.
- Evolving design provisions: seismic standards for rack structures are an active and growing area of standardisation, with a significant share of existing installations erected before the latest guidance became available.
The Case for Retrofitting
Post-earthquake surveys have documented numerous cases of rack damage and collapse, highlighting the real-world consequences of inadequate seismic performance. Given the volume of existing rack installations across Europe — and the cost and environmental impact of mass replacement — targeted seismic retrofitting represents a rational, proportionate, and sustainable response to the problem. SAVERACK is developing the tools and knowledge to make this response practical and accessible.