prEN 1991-4

1.1  Scope of EN 19914
(1) EN 1991-4 provides guidance 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 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 standard 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 may be used for the structural assessment of existing construction, in developing the design of repairs and alterations or for assessing changes of use.
NOTE  Where the structural appraisal of an existing structure is being considered, reference can be made to the National Annex and to the client concerning the relevance of the current standard.
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 covered by this document:
-  the silo here defined is either an isolated structure or can be part of a battery of silos. For a silo battery, the term silo is used throughout this standard to refer to a single cell within the battery;
-  the silo planform cross-section shapes are limited to those shown in Figure 1.1c.
NOTE 1  Minor variations to these shapes can be accepted provided the structural consequences of the resulting changes in pressure are expected to be considered. Further information concerning planform cross-section geometries is given in 7;
NOTE 2  Further information concerning planform cross-section geometries is given in Clause 7.
-  the relevant overall height of the silo hb (Figure 1.1a) is measured from the level of the equivalent surface of the stored solid (see 3.2.17) when the silo is filled to its maximum capacity, down to the apex of the cone of the hopper or to the flat base where there is no hopper;
NOTE  For the evaluation of ho to calculate hb, see (2).
-  the effective diameter dc of the silo should be determined as indicated in Figure 1.1c;
-  the following dimensional limitations on the overall height hb and aspect ratio hb/dc apply (see Figure 1.1):
hb/dc < 10  (1.1)
hb < 100 m  (1.2)
dc < 60 m  (1.3)
-  the structural transition lies in a single horizontal plane (see Figure 1.1a);
-  the relevant cylindrical section height of the silo hc (Figure 1.1a) should be measured from the level of the equivalent surface of the stored solid (see 3.2.17) when the silo is filled to its maximum capacity, down to the structural transition (see Figure 1.1a) or to the flat base where there is no hopper;
(2) For a symmetrically filled circular silo of diameter dc, h0 should be determined as:
  (1.4)
and for a symmetrically filled rectangular silo of characteristic dimension dc, h0 should be determined as:
  (1.5)
where:
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