Standards Development

Scope

(1) EN 1993 4 1 provides rules for the structural design of steel silos of circular or polygonal plan-form, being free-standing (on ground) or supported on a structural framework (elevated).

(2) This document is applicable to silos constructed from isotropic rolled plates that are stiffened or unstiffened, from corrugated sheeting that is stiffened or unstiffened and from flat or corrugated plates assembled into box structures of different geometries. It applies to vertical walls, hoppers, roof structures and transition junctions.

(3) This document does not apply to storage vessels for silage and haylage, or to the storage of materials that are not free-flowing (see EN 1991 4). This Part 4-1 also does not cover:

— design for resistance to fire;

— cylindrical silos with internal subdivisions;

— internal structures within a single silo (except for internal ties, as defined in 12.5);

— silos in Silo Group 0, although they can be treated as silos in Silo Group 1; 

— silos in Silo Group 4, because the provisions in the Eurocodes do not entirely cover design rules needed for structures classified as CC4. For these structures, additional provisions to those given in the Eurocodes can be needed;

— design of externally supported hoppers (a hopper that is mounted on a structural framework or with columns beneath the body of the hopper);

— cases where special measures are necessary to limit the consequences of accidents.

(4) This document is applicable to silos within the following dimensional limits:

— overall aspect ratio of the silo hb/dc < 10

— relevant overall height of the silo hb < 70 m

— effective diameter of the silo dc < 60 m

NOTE These dimensional limitations are more limited than those of EN 1991 4, which also applies to silos constructed from other materials.

(5) Where this document applies to circular planform silos, the geometric form is restricted to axisymmetric structures, but unsymmetrical actions on them, vertical stiffeners and supports that induce forces in the silo structure that are not axisymmetric are included.

(6) This part is concerned only with the requirements for resistance and stability of steel silos. For other requirements (such as operational safety, functional performance, fabrication and erection, quality control, details like circular man-holes, flanges, filling devices, outlet gates and feeders, etc.), see other relevant standards and information.

(7) This part is concerned with both isolated silo structures and silos that are connected to others to form a battery of silos. Throughout this document the term silo refers to an isolated silo or a single cell within a battery.

(8) Provisions relating to special requirements of seismic design are provided in EN 1998 4, which complements or adapts the provisions of Eurocode 3 specifically for this purpose.

(9) The structural design of supporting structures for the silo are dealt with in EN 1993 1 1. The supporting structure is deemed to consist of all structural elements beneath the bottom flange of the lowest ring of the silo or its skirt (see Figure 1.1), though information on some forms of support structure is given in Clause 8 of this document.

(10) Foundations in reinforced concrete for steel silos are dealt with in EN 1992 (all parts) and EN 1997 (all parts). 

(11) For silo structures equipped with vibrating machinery, flowing aids on hoppers, pneumatic devices etc., additional provisions to those given in this document can be needed.

(12) Silos that are used to store materials that can induce vibrations, oscillations and shocks (quaking, honking, banging: see EN 1991 4) require special load assessments and design considerations that are outside the scope of this document.

Purpose

This amendment corrects technical and editorial points in EN 1993-4-1:2026, in order to correct typos, eliminate technical errors, remove ambiguities, enhance ease-of-use, etc.

The following main changes to EN 1993-4-1:2026 are included in the amendment:

 — clarifications on the choice of the Structural Complexity Class depending on the parameter w (Table 4.1),

— correction of the method to determine the necessary top ring stiffness for an open silo to resist buckling under external pressure, internal vacuum and wind (subclause 7.5.2),

— correction of several wordings and typing errors throughout the document.