Standards Development

Scope

1.1 Scope of EN 1993-4-1

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

(2) prEN 1993‑4‑1 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, transition junctions and support structures.

(3) prEN 1993‑4‑1 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:

—       resistance to fire;

—       cylindrical silos with internal subdivisions;

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

—       silos with capacity less than 100 kN (10 tonnes);

—       hoppers that are supported on a structural framework;

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

(4) This document is applicable to silos within the following dimensional limits (see EN 1991-4):

—       Silo aspect ratio hb/dc < 10  

—       Silo total height hb < 70 m

  —       Silo equivalent diameter 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 standard applies to circular planform silos, the geometric form is restricted to axisymmetric structures, but unsymmetrical actions on them 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 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, but throughout this document the term silo refers to 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 (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).

1.2 Assumptions

(1) Unless specifically stated, the provisions of EN 1990, EN 1991 (all parts) and EN 1993‑1 (all parts) apply.

(2) The design methods given in EN 1993‑4‑1 are applicable if:

—       the execution quality is as specified in EN  1090‑2, and

—       the construction materials and products used are as specified in the relevant parts of EN 1993 (all parts), or in the relevant material and product specifications.

a) Circular planform silo

Please see daft for Figure 1.1 — Terminology used in silo structures