Introduction - Assessment and Refurbishment of Steel Structures - page 14

(1.13)

(1.14)

and where
E k and
R k

are characteristic values of load effects and structure resistance,

γ f is a partial safety factor for load effects considering adverse deviations of loading from

their representative values,

γ F is a partial safety factor for load effects, considering model uncertainties and dimension

deviations,

γ m is a partial factor for material properties,

γ M is a partial safety factor for materials, considering model uncertainties and dimension

deviations,

γ Ed is a partial factor considering uncertainties of the model of load response,

γ Rd is a partial factor considering uncertainties of the resistance model,

α nom is the nominal value for a geometric characteristic,

α d is a design value for a geometric characteristic, where α d = α nom ±∆ α .

On condition of the proportionality of load effects E to the action F and model
uncertainties, we get the following relations for the partial factors γ F and γ M

(1.15)

(1.16)

1.3.2.5 Application of the partial factor method in assessing the reliability
of existing structures

In assessing reliability of existing structures, it is necessary to consider certain
differences they may have in comparison with newly designed structures. The primary
differences are:

• Existing structures are periodically checked via inspections and diagnostic inquiries
whose results represent a source of information that can reduce uncertainties in the
input parameters involved in verifying their reliability.
• The reliability of the existing structure is verified for residual lifetime, not for its
planned lifetime, as is the case with a design of a new structure.

When verifying the reliability of a new structure, it is necessary to consider possible
imperfections of the system or its elements. These are to be considered in terms of the
relevant by norms for the various design values. With existing structures, this