Design values permanent actions

Design situation Permanent actions G d Variable Actions One with its Others with their characteristic value combination value Accidental actions A d... 

The following value for the partial safety factor for the action may be obtained from 2.3.3.1, Table 2.2 of the EUROCOMP Design Code (Permanent actions only,... 

EN 1990 (2002) introduces for the fundamental combination of actions in permanent and transient design situations (ULS of type STR) three alternative procedures, denoted here as A, B and C. Considering for simplicity one permanent action G and two variable actions Q (e.g. imposed loads) and W (wind actions), the exp. (6.10) of the combination rule A is given in EN 1990 for the design value of action effect as... 

The probabilistic models of actions are related to their characteristic values used for the determination of the design values of actions (see Table 1). The permanent action is described by normal distribution (N), variable actions by Gumbel distribution (GUM) and material strength by lognormal distribution (LN). These models are primarily intended as conventional models in time invariant reliability analysis of structural members using Turkstra s combination rule, see e.g. Holicky (2013). 

Gddnf Lower design value of a permanent action... 

Yc.mf Partial safety factor for permanent actions, in calculating the lower design values... 

P(3) The upper and lower design values of permanent actions are expressed as follows (see 2.2.2.2) ... 

Gig=characteristic values of permanent actions Qk,i=characteristic value of one of the variable actions Qk,i=characteristic values of the other variable actions Ad=design value (specified value) of the accidental action ycj=partial safety factors for permanent action j YGAj=as ygj, but for accidentcd design situations YQ,i=partial safety factors for variable action i Vo. Vi, V2=coefficients defined in 2.2.2.3 Imposed deformations should be considered where relevant. 

P(l) In the various combinations defined above, those permanent actions that increase the effect of the variable actions (i.e. produce unfavourable effects) shall be represented by their upper design values, those that decrease the effect of the variable actions (i.e. produce favourable effects) by their lower design values (see 2.2.2.4). 

Presently available information indicates that most European countries have adopted the values of partial factors and other reliability elements recommended in Eurocode EN 1990 (2002) for the basis of structural design. About half of the countries are applying an exp. (6.10) for verification of structures for the Ultimate Limit States (ULS) and other countries exps. (6.10a,b). Both alternatives (6.10) or (6.10a,b) are allowed to be use in some CEN countries including the Czech Republic (limitations in some countries for application of (6.10a,b) are given). Modified exps. (6.10a , b) are applied in few countries where in the first expression the permanent actions are considered only. Some countries which preferred exps. (6.10a,b) increased the value of reduction factor for permanent actions from the recommended value 0.85 up to 0.93 diminishing the difference in application of both alternative load combinations. Therefore, the reliability of structures designed according to the nationally implemented Eurocodes may differ from country to country (allowed by EC as a matter of their national safety). 

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