Compression

Bending c) Calculation of 5 for C and Z sections

Figure 4.1: Determination of spring stiffness

(3) In determining the values of the rotational spring stiffnesses Ce, Ce i and C$ 2 from the geometry of the cross-section, account should be taken of the possible effects of other stiffeners that exist on the same element, or on any other element of the cross-section that is subject to compression.

(4) For an edge stiffener, the deflection 8 should be obtained from:

with:

(5) In the case of the edge stiffeners of lipped C-sections and lipped Z-sections, Cd should be determined with the unit loads u applied as shown in figure 4.1(c).

(6) For an intermediate stiffener, as a conservative alternative the values of the rotational spring stiffnesses CQ x and Cd 2 may be taken as equal to zero, and the deflection 5 may be obtained from:

(7) The reduction factor x for the flexural buckling resistance of a stiffener should be obtained from 6.2.1(2)P using buckling curve a0 (imperfection factor a = 0,13) for the relative slenderness X from:

crcr s is the elastic critical stress for the stiffener from 4.3.2, 4.3.3 or 4.3.4. 4.3.2 Plane elements with edge stiffeners 4.3.2.1 Conditions

(1) An edge stiffener may be either a single edge fold or a double edge fold as illustrated in figure 4.2.

(2)P An edge stiffener shall not be taken into account in determining the resistance of the plane element to which it is attached unless the following conditions are met:

- the angle between the stiffener and the plane element is not less than 45° and not more than 135°;

- the outstand c is not less than 0,2bp, where bp and c are as shown in figure 4.2;

- the ratio bp /1 is not more than 60 for a single edge fold stiffener, or 90 for a double edge fold stiffener.

(3) If the criteria in (1) and (2)P are met, the effectiveness of the stiffener may be determined from either:

- the general procedure given in 4.3.2.2;

- the simplified procedure given in 4.3.2.3.

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