CSLLPP guidelines and UNI EN 16681: what changes for racking in seismic zones

Two instruments, one goal

UNI EN 16681 is the European product standard for the seismic design of adjustable pallet racking. The guidelines of the Italian Consiglio Superiore dei Lavori Pubblici (Central Technical Service) — Guidelines for the design, execution, verification and safety upgrading of steel racking — do not replace the European standard: they integrate and adapt it to Italy, placing it within the NTC system and also covering aspects that EN 16681 does not address, such as existing racking and its safety upgrading.

Which standard applies

The guidelines set out, according to type and height, which reference to adopt:

Type	Upright frame height	Standard
Self-supporting (clad-rack)	Any	NTC
Internal / external	≤ 14 m	UNI EN 16681 + guideline prescriptions (§6.2)
Internal / external	> 14 m	NTC

New racking in seismic zones may never be designed without a seismic approach.

The Italian integrative prescriptions on EN 16681

Where EN 16681 applies, the guidelines introduce additional prescriptions valid throughout Italy. The main ones:

Aspect (EN 16681 ref.)	CSLLPP guideline prescription
Seismic design obligation (§5.1)	Extended to the whole country where, for the life-safety limit state, ag·S ≥ 0.05 g
Seismic action and spectrum (§6.1, 6.4–6.6)	Defined according to the NTC
Viscous damping (§6.2)	ξ = 5% (up to 8% only with documented experimental evidence)
Reference period (§6.3)	VR ≥ 50 years
Second-order effects (§7.4.1)	θ < θmax = 0.5
Spectrum modification (§7.5)	ED1 = ED2 = ED3 = 1.0 (no reduction)
Design masses (§7.5.4)	NTC seismic combination, ψ factors for Category E — Storage (ψ2,1 ≤ 1)
Base plates and anchors (§8.1.6)	Designed with non-dissipative behaviour; post-installed anchors per NTC ch.12 and UNI EN 1992-4
Partial factors (§9.2.1.3)	In accordance with the NTC

A central point concerns the behaviour factor q: in Italy the maximum value for low-dissipative behaviour is set at q = 1.5 (for both braced and moment-frame solutions). For higher values the design must follow the dissipative-behaviour rules, with behaviour factors validated by experimental tests (e.g. pushover tests on a full-scale specimen, Annex B) or by numerical models calibrated against test data.

The added value: existing racking

EN 16681 deals with new design. The guidelines, also drawing on the technical experience of the post-earthquake interventions in Emilia (2012), devote a broad section to existing racking: seismic vulnerability assessment by a qualified engineer, systematic checks on the components (uprights, base plates, anchors, beams, connectors) and — pending the full assessment — load restrictions according to the racking class (use limited to 2/3 or 1/2 of the levels from the bottom). The experimental determination of capacities and of the behaviour factor through dedicated tests is also provided for.

What it means in practice

For the employer and the client, the guidelines clarify when to apply EN 16681 and when the NTC, set prudent design parameters and define the duties on existing installations. Stefano Luise Engineering S.r.l. works across this whole scope: design and verification of new racking, vulnerability assessment and safety upgrading of existing racking, experimental testing and documentation management, with a single technical point of contact.

Regulatory references

CSLLPP Guidelines — Steel racking  •  UNI EN 16681  •  UNI EN 15512  •  UNI EN 15620  •  UNI EN 15635  •  NTC 2018  •  UNI EN 1993-1-1/1-3/1-8  •  UNI EN 1992-4  •  Italian Legislative Decree 81/2008

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