Figure 5.2: Effective cross-section for resistance to bending moments

5.4.2 Partially plastic resistance

(1)P Provided that bending moment is applied only about one principal axis of the cross-section, and provided that yielding occurs first at the tension edge, plastic reserves in the tension zone may be utilized without any strain limit until the maximum compressive stress ffcom,Ed reaches /yb^TMi •

(2) In this case, the effective partially plastic section modulus ^pp eff should be based on a stress distribution that is bilinear in the tension zone but linear in the compression zone.

(3) In the absence of a more detailed analysis, the effective width Z?eff of an element subject to stress gradient may be obtained using 4.2 by basing bc on the bilinear stress distribution, but ignoring the shape of the stress distribution in determining

(4) If redistribution of bending moments is assumed in the global analysis, it should be demonstrated from the results of tests in accordance with Section 9 that the provisions given in 7.2 are satisfied.

(5)P Plastic reserves may also be utilized in the compression zone, up to the strain specified in (6)P, provided that all the following conditions are satisfied:

a) Bending moment is applied only about one principal axes of the cross-section;

b) The member is not subject to torsion, or to torsional, torsional-flexural or lateral-torsional buckling;

c) Distortion of compressed parts of the cross-section is prevented;

d) The angle between any web and the vertical does not exceed 30

e) The slant height sc of the compressed portion of the web satisfies:

(6)P The compressive strain ecom Ed shall not exceed Cyey/ym , where ey = /yb/£, see figure 5.3, and the factor Cy is obtained from the following:

- for doubly supported compression elements without intermediate stiffeners:

if IMyjÊif^ < sjt < 1,29(Ë!fyb [i.e. if 33,18a < sjt < 38,56e]:



- for outstand elements:

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