scope:

Scope of EN 1991 - Eurocode 1

(1)P EN 1991 provides general principles and actions for the structural design of buildings and civil engineering works including some geotechnical aspects and shall be used in conjunction with EN 1990 and EN 1992-1999.

(2) EN 1991 also covers structural design during execution and structural design for temporary structures. It relates to all circumstances in which a structure is required to give adequate performance.

(3) EN 1991 is not directly intended for the structural appraisal of existing construction, in developing the design of repairs and alterations or for assessing changes of use.

(4) EN 1991 does not completely cover special design situations which require unusual reliability considerations such as nuclear structures for which specified design procedures should be used.

Scope of EN 1991-4 actions on structures: silos and tanks

(1)P This part provides general principles and actions for the structural design of silos for the storage of particulate solids and tanks for the storage of fluids and shall be used in conjunction with EN 1990, other parts of EN 1991 and EN 1992 to EN 1999.

(2) This part includes some provisions for actions on silo and tank structures that are not only associated with the stored solids or liquids (e.g. the effects of thermal differentials, aspects of the differential settlements of batteries of silos)

(3) The following geometrical limitations apply to the design rules for silos:

− the silo cross-section shapes are limited to those shown in Figure 1.1d, though minor variations may be accepted provided the structural consequences of the resulting changes in pressure are considered;

− the following dimensional limitations apply:

h_b/d_c < 10

h_b < l00 m

d_c < 60 m

− the transition lies in a single horizontal plane (see Figure 1.1a);

− the silo does not contain an internal structure such as a cone or pyramid with its apex uppermost, crossbeams, etc. However, a rectangular silo may contain internal ties.

(4) The following limitations on the stored solids apply to the design rules for silos:

− each silo is designed for a defined range of particulate solids properties;

− the stored solid is free-flowing, or the stored solid can be guaranteed to flow freely within the silo container as designed (see 1.5.12 and Annex C);

− the maximum particle diameter of the stored solid is not greater than 0,03dc (see Figure 1.1d).

NOTE: When particles are large compared to the silo wall thickness, account should be taken of the effects of single particles applying local forces on the wall.

(5) The following limitations on the filling and discharge arrangements apply to the design rules for silos:

− filling involves only negligible inertia effects and impact loads;

− where discharge devices are used (for example feeders or internal flow tubes) solids flow is smooth and central.

(6) Only hoppers that are conical (i.e. axisymmetric), square pyramidal or wedge-shaped (i.e. with vertical end walls) are covered by this standard. Other hopper shapes and hoppers with internals require special considerations.

(7) Some silos with a systematically non-symmetric geometry are not specifically covered by this standard. These cases include a chisel hopper (i.e. a wedge hopper beneath a circular cylinder) and a diamond-back hopper.

(8) The design rules for tanks apply only to tanks storing liquids at normal atmospheric pressure.

(9) Actions on the roofs of silos and tanks are given in EN 1991-1-1, EN 1991-1-3 to EN 1991-1-7 and EN 1991-3 as appropriate.

(10) The design of silos for reliable solids discharge is outside the scope of this standard.

(11) The design of silos against silo quaking, shocks, honking, pounding and silo music is outside the scope of this standard.

NOTE: These phenomena are not well understood, so the use of this standard does not guarantee that they will not occur, or that the structure is adequate to resist them.