8 Design of transition junctions and supporting ring girders
8.1 Basis
8.1.1 General
(1) A steel transition ring or ring girder should be so proportioned that the basic design
requirements for the ultimate limit state given in section 2 are satisfied.
(2) The safety assessment of the ring should be carried out using the provisions of EN 1993-1-6,
except where the provisions of this Standard are deemed to satisfy them.
(3) For silos in Consequence Class 1, the cyclic plasticity and fatigue limit states may be ignored,
provided that the following conditions are met.
8.1.2 Ring design
(1) The ring or ring girder should be checked for:
− resistance to plastic limit under circumferential compression;
− resistance to buckling under circumferential compression;
− resistance to local yielding under tension or compression stresses;
− resistance to local failure above supports;
− resistance to torsion;
− resistance of joints (connections).
(2) The ring girder should satisfy the provisions of EN 1993-1-6, except where 8.2 to 8.5 provide
conditions that are deemed to satisfy the provisions of that standard.
(3) For silos in Consequence Class 1, the cyclic plasticity and fatigue limit states may be ignored.
8.1.3 Terminology
(1) A ring whose purpose is only to provide resistance to radial components of forces from the
hopper should be termed a ‘transition ring’.
(2) A ring whose purpose is to provide redistribution of vertical forces between different
components (e.g. the cylinder wall and discrete supports), should be termed a ‘ring girder’.
(3) The point of intersection between the middle surface of the hopper plate and the middle surface
of the cylindrical shell wall at the transition junction, termed the ‘joint centre’, should be used as the
reference point in limit state verifications.
(4) A silo with no identified ring at the transition (see figure 8.1) has an effective ring formed from
adjacent shell segments and should be termed a ‘natural ring’.
(5) An annular plate placed at the transition junction should be termed an ‘annular plate ring’, see
figure 8.1.
(6) A hot rolled steel section, used as a ring stiffener at the transition should be termed a ‘rolled
section ring’.
(7) A rolled steel section rolled around the silo circumference and used to support the shell beneath
the transition should be termed a ‘rolled ring girder’.