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Steel Designers' Manual - 6th Edition (2003)
1060 The Eurocodes
imperfections at height/200 (or an equivalent horizontal force) are similar to BS
5950-1. Imperfections of the bracing system are both more rigorous and require
more design effort than current UK practice.
Frame analysis
The analysis is required to take account of the effects of the deformed geometry on
the structure. First order analysis may be used where the increases in internal forces
and moments are less than 10%. This implies a critical load ratio (lcr), under
factored loading, of more than 10; it is equivalent to the BS 5950-1: 2000 ‘nonsway’
frame approach.
A range of second order approaches may be used for structures for which gcr is
less than 10. These methods include:
• effective length approaches
• amplification factors
• energy methods
• formal second order analysis.
36.3.4 Supporting standards
Relevant supporting standards include those for:
• Steel properties
• Tolerances on steel sections and plates
• Ordinary bolts
• HSFG bolts
• Welding electrodes
• Fabrication and erection.
Steel properties
Properties of structural steels are currently given in EN 10025, EN 10113, EN 10137,
EN 10155, EN 10210 and EN 10219, the last two covering structural hollow sections.
A new edition of EN 10025 is planned that will combine all of these except steel
for hollow sections (and may include these also). All of these have been adopted as
BS EN standards.
Further BS EN standards are available covering steel sheets and strip, both plain
and galvanized, for use in cold-formed sections and sheeting. They are already in
use in connection with BS 5950 Parts 5, 6, 7 and 9.