Introduction - The Behaviour and Design of Steel Structures to EC3 - page 17

4 Buckling

Load

1 Linear

3 Geometric non-linearity

2 Material non-linearity

5

Material and geometric
non-linearity

Deformation

Figure 1.14 Structure behaviour.

involveyieldingofsometensionmembers,orbucklingeitherofsomecompression
members or of the frame, or both. In flexural structures, failure is associated with
full plasticity occurring at a sufficient number of locations that the structure can
formacollapsemechanism.Instructureswithbothaxialandflexuralactions,there
is an interaction between yielding and buckling (curve 5 in Figure 1.14), and the
failure load is often difficult to determine. The transitions shown in Figure 1.14
betweentheelasticandultimatebehaviouroftentakeplaceinaseriesofnon-linear
steps as individual elements become fully plastic or buckle.

1.5 Loads

1.5.1 General

The loads acting on steel structures may be classified as dead loads, as imposed
loads,includingbothgraduallyappliedanddynamicloads,aswindloads,asearth
or ground-water loads, or as indirect forces, including those due to temperature
changes, foundation settlement, and the like. The more general collective term
Actions is used throughout the Eurocodes. The structural engineer must evaluate
the magnitudes of any of these loads which will act, and must determine those
which are the most severe combinations of loads for which the structure must be
designed.Theseloadsarediscussedinthefollowingsubsections,bothindividually
and in combinations.

1.5.2 Dead loads

Thedeadloadsactingonastructurearisefromtheweightofthestructureincluding
the finishes, and from any other permanent construction or equipment. The dead