Control of design and construction

The requirement on control of design and construction of steel buildings in EN 1998-1 Clause 6.11

reflects the concern expressed in Section 6.3 about creating the conditions for an effective global dissipative behaviour of the structure. This goal requires in particular that the yield stress of all materials used in the dissipative components remains within well-defined ranges, notably below an upper bound value. The complete background of these requirements has been given in Section 6.3.

Regarding problems with materials provided on site, three types of reaction can be envisaged:

(1) If the yield stress of the material of dissipative zones exceeds the standard upper bound of 1.1/ max, the capacity design calculations in the design should be repeated, considering in these checks the real yield stresses of the materials.

(2) If the problem persists, a pushover non-linear analysis of the structure can be made to provide an explicit evaluation of the global plastic mechanism, including the first yield and the ultimate load, which may prove satisfactory, even if some criteria in EN 1998-1 are not fulfilled.

(3) Another option in the case of material overstrength is to reduce the sections of dissipative zones so that their real strength, Rd act, comes closer to the design strength, Rd. In moment frames, this approach makes use of the reduced beam section design mentioned in Section 6.9. A similar approach can be used in other typologies of structures. In all cases, special care has to be taken to achieve a length of the yield zone large enough to provide the needed rotation/elongation/shear deformation capability. The section reduction technique also requires that the surface aspect of the 'shaved' sections be appropriate: rough surfaces produced by oxygen cutting, for instance, cannot stay rough and must be machined out.

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