Introduction - Composite Structures of Steel and Concrete - page 7

Table 1.1 Values of γ G and γ Q for persistent design situations

Type of action Permanent Permanent Variable Variable

unfavourable favourable unfavourable favourable

Ultimate limit states 1.35* 1.35* 1.5 0

Serviceability limit states 1.0 1.0 1.0 0

*Except for checking loss of equilibrium, or where the coefficient of variation is large

where the function E represents the process of structural analysis. Where
the effect is an internal force or moment, verification for an ultimate limit
state consists of checking that

E d ≤ R d (1.4)

where R d is the relevant design resistance of the system or member or
cross-section considered.

1.3.2.2 Resistances

Resistances, R d , are calculated using design values of properties of mater-
ials, X d , given by

X d = X k / γ M (1.5)

where X k is a characteristic value of the property and γ M is the partial

factor for that property.
The characteristic value is typically a 5% lower fractile (e.g., for
compressive strength of concrete). Where the statistical distribution is not
well established, it is replaced by a nominal value (e.g., the yield strength
of structural steel), so chosen that it can be used in design in place of X k .
The subscript M in γ M is often replaced by a letter that indicates the

material concerned, as shown in Table 1.2, which gives the values of

γ M

Table 1.2 Recommended values for γ M for strengths of materials and for

resistances

Material Structural Profiled Reinforcing Concrete Shear

steel sheeting steel connection

Property f y f y f sk f ck or f cu P Rk

Symbol for γ M γ A γ A γ S γ C γ V or γ Vs

Ultimate limit states 1.0 1.0 1.15 1.5 1.25

Serviceability limit states 1.0 1.0 1.0 1.0 1.0

Notation: for concrete, f ck and f cu are respectively characteristic cylinder and cube strengths; symbol γ Vs is

for shear resistance of a composite slab.