Introduction - The Behaviour and Design of Steel Structures to EC3 - page 7

reanalysethestructuredesigned,andthesearecarriedoutwithmoreprecisionthan
was either possible or appropriate for the preliminary analysis. The performance
ofthestructureisthenevaluatedinrelationtothestructuralrequirements,andany
changesinthememberandjointsizesaredecidedon.Thesechangesmayrequire
a further reanalysis and re-proportioning of the structure, and this cycle may be
repeated until no further change is required.Alternatively, it may be necessary to
modifytheoriginalstructuralsystemandrepeatthestructuraldesignprocessuntil
a satisfactory structure is achieved.
The alternative overall systems are then evaluated in terms of their service-
ability, economy, and harmony, and a final system is selected, as indicated
in Figure 1.4. This final overall system may be modified before the design is
finalised. The detailed drawings and specifications can then be prepared, and
tenders for the construction can be called for and let, and the structure can
be constructed. Further modifications may have to be made as a consequence
of the tenders submitted or due to unforeseen circumstances discovered during
construction.
This topic is concerned with the structural behaviour of steel structures, and
therelationshipsbetweentheirbehaviourandthemethodsofproportioningthem,
particularly in relation to the structural requirements of the European steel struc-
tures code EC3 and the modifications of these are given in the NationalAnnexes.
Thiscodeconsistsofsixparts,withbasicdesignusingtheconventionalmembers
being treated in Part 1. This part is divided into 12 sub-parts, with those likely to
be required most frequently being:
Part 1.1 General Rules and Rules for Buildings [8],
Part 1.5 Plated Structural Elements [16],
Part 1.8 Design of Joints [17], and
Part 1.10 Selection of Steel for Fracture Toughness and Through-Thickness
Properties [18].
Otherpartsthatmayberequiredfromtimetotimeinclude:Part1.2thatcovers
resistance to fire, Part 1.3 dealing with cold-formed steel, Part 1.9 dealing with
fatigue and Part 2 [19] that covers bridges. Composite construction is covered by
EC4 [20]. Since Part 1.1 of EC3 is the document most relevant to much of the
content of this text (with the exception of Chapter 9 on joints), all references to
EC3madehereinshouldbetakentomeanPart1.1[8],includinganymodifications
given in the NationalAnnex, unless otherwise indicated.
Detailed discussions of the overall design process are beyond the scope of this
topic, but further information is given in [13] on the definition of the design
problem, the invention of solutions and their evaluation, and in [21-24] on the
execution of design. Further, the conventional methods of structural analysis are
adequately treated in many textbooks [25-27] and are discussed in only a few
isolated cases in this topic.