Introduction - The Behaviour and Design of Steel Structures to EC3 - page 21

Table 1.1 Partial load factors for common situations

Ultimate limit state Permanent actions γ G Variable actions γ Q

Unfavourable Favourable Unfavourable Favourable

EQU 1.1 0.9 1.5 0

STR/GEO 1.35 1.0 1.5 0

thus to use all the persistent actions G k , j such as self-weight and fixed equipment
with a leading variable action Q k ,1 such as imposed, snow, or wind load, and
reducedvaluesoftheothervariableactions Q k , i .MoreinformationontheEurocode
approach to loading for steel structures is given in [39-41].
This approach is applied to the following forms of ultimate limit state:

EQU = loss of static equilibrium of the structure on any part of it
STR = failure by excessive deformation, transformation of the structure or
any part of it into a mechanism, rupture or loss of stability of the
structure or of any part of it
GEO = failure or excessive deformation of the ground
FAT = fatigue failure

For the most common set of design situations, use of the appropriate values from
[41] gives the load factors ofTable 1.1.
Using the combination factors of ψ 0 = 0.7 and 0.5 of [41] for most variable
actions and wind actions, respectively leads to the following common STR load
combinations for buildings:

1.35 G + 1.5 Q I + 0.75 Q W
1.35 G + 1.05 Q I + 1.5 Q W
− 1.0 G + 1.5 Q I , and
− 1.0 G + 1.5 Q W .

in which the minus signs indicate that the permanent action is favourable.

1.6 Analysis of steel structures

1.6.1 General

In the design process, the assessment of whether the structural design require-
ments will be met or not requires the knowledge of the stiffness and strength of
thestructureunderload,andofitslocalstressesanddeformations.Thetermstruc-
tural analysis is used to denote the analytical process by which this knowledge