1.1 Scope of EN 1991-4
(1) EN 1991-4 provides rules for calculating actions for the structural design of silos and tanks.
NOTE 1 Silos are used for the storage of particulate solids. Tanks are used for the storage of liquids.
NOTE 2 For limitations on rules for silos given in this document, see 1.3.
NOTE 3 For limitations on rules for tanks given in this document, see 1.4.
(2) EN 1991-4 includes some provisions for actions on silo and tank structures that are not only associated with the stored particulate solids or liquids (e.g. the effects of thermal differentials) but substantially affected by them.
NOTE Liquid loads on tanks are very precisely defined. Many loads on silos are not known with great precision. This document provides guidance for many practical situations for which very limited certain knowledge is available, and the information is derived from the limited experimental and analytical information available, coupled with conclusions drawn from failure investigations. The information is not based on a sound statistical treatment of experimental data.
(3) EN 1991-4 is intended for use with concrete, steel, aluminium, timber and FRP storage structures.
NOTE FRP is the standard acronym for fibre reinforced polymer materials.
(4) EN 1991-4 is also applicable for the structural assessment of existing silos and tanks, unless otherwise specified by the relevant authority or, if not specified, agreed between the relevant parties for the specific project.
NOTE 1 Changes in filling or discharge arrangements, changes in the wall friction of inner surfaces, or in the use of the silo, including storage of different particulate solids, can be reasons for assessing existing silos.
NOTE 2 Differentiation of the liquid stored can be a reason for assessing existing tanks.
1.2 Assumptions
(1) The assumptions of EN 1990 apply.
(2) EN 1991-4 is intended to be used in conjunction with EN 1990, with the other parts of EN 1991, EN 1992, EN 1993, EN 1995, EN 1997, EN 1998 and EN 1999 where relevant to the design of silos and tanks.
1.3 Limitations on silos
1.3.1 Geometrical limitations
(1) The following geometrical limitations apply to the design rules for silos and silo batteries (see 3.2.59 and 3.2.60) covered by this document:
- the silo planform cross-section shapes are limited to those shown in Figure 1.1c.
NOTE 1 Further information concerning planform cross-section geometries is given in Clause 7.
NOTE 2 For the determination of the effective diameter dc of the silo see Figure 1.1c;
- the following dimensional limitations on the aspect ratio for free-standing single cell silos hc/dc, the overall height hb and the effective diameter dc apply (see Figure 1.1):
hc/dc < 10 (1.1)
hb < 100 m (1.2)
dc < 60 m (1.3)
NOTE 3 See Figure 1.1 for hc, dc and hb.
- the structural transition lies in a single horizontal plane (see Figure 1.1a);
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