Actions characteristic values

Redesign of variable actions Characteristic values and partial factors need not be modified, except for the following cases ... 

Now transform the system (5.99)-(5.102) to a dimensionless form. To this end, introduce the characteristic values of length I, velocity U and time z. Notice that the characteristic time is natural in problems, in which processes under the external, time-varying actions are considered. We denote as z the characteristic time of such an action. In many problems z is not an independent value, and is determined as T = I/U. 

The assessment is based on design values of basic variables derived from characteristic values and partial factors. Partial factors of the actions with unfavourable effects and of resistance with a favourable effect on structural reliability are defined as follows, respectively ... 

The imcertainties of action effects and structural resistance were considered in accordance of the Eurocode 1990 and JCSS using calibration methods to define the variable parameters (see tab.l). A sod stiffness variabiUty in the vertical direction is defined by the characteristic stiffness value Kk from the geological measurement and the variable factor k,ar- The stiffness of the structure is determined with the characteristic value of Young s modulus Mk and variable factor m ar The action effects are taken with characteristic values Gk, Qk, Sk, Wk and variable factors g ar, qvar, var and... 

The Backgroimd document (1999) provides additional information about experimental measurements of temperatures which formed the basis for the development of the models of thermal actions given in Eurocodes. The characteristic values of temperature components are based on the fifty years return period like other climatic actions (snow, wind velocity, icing). Presently, the Eurocodes recommend a unique value of partial factor yg = 1,5 for most variable actions Q with respect to the ultimate limit states. However, the reduced factor yr = 1, 2 may be applied for thermal actions in some national standards, CSN 73 6203 (1986). It appears that the partial factors for some variable actions might be differentiated taking into account their characteristics. 

The climatic actions may often be described by the Extreme value distributions. The characteristic value of a climatic action is defined in Eurocodes as the upper fractile of the probabilistic distribution for the basic time period corresponding to the 2% probabihty of atmual exceeding. The design value of a climatic action is considered as 0,996% fractile of the probabilistic distribution for structures in the reUabUity class RC2. 

Gkdnf Lower characteristic value of a permanent action... 

P(2) For permanent actions where the coefficient of variation is large or where the actions are likely to vary during the life of the structure (e.g. for some superimposed permanent loads), two characteristic values are distinguished, an upper (Gk sup) and a lower (Gp j f). Elsewhere a single characteristic value (Gp) is sufficient. 

P(4) For variable actions the characteristic value (Qp) corresponds to either ... 

For accidental actions the characteristic value Ak (when relevant) generally corresponds to a specified value. 

A material strength, or other property may have two characteristic values, an upper and a lower. In most cases only the lower value will need to be considered. In some cases, higher values may be adopted, depending on the type of problem considered, e.g. the modulus of elasticity when considering the effects of indirect actions and strength where overstrength effects may lead to a reduction in safety. 

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

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. 

Bbrner has given a characteristic value k which expresses the time of action of the... 

Control operators are a special set of operators that specify which precedence edge is taken when leaving a basic block. In addition to specifying control flow, control operators also specify the data flow characteristics of the control action which values are used, and which new values are produced as a consequence of the control action. Specific control operators support conditional control flow, loops, and procedures. 

Characteristic values and partial factors of the basic variables and notation are provided in Table 5. Soil parameters are based on a geotechnical survey (five tests) characteristic value of the wind action effect is obtained from a National Annex to EN 1991-1-4 (2005). The most unfavorable results are obtained using Design Approach 1—Combination 2, EN 1997-1 (2004). 

To investigate resulting load effects under various intensities of variable actions, the characteristic values of actions G, and W. are related using quantity x given as the ratio of variable actions Q +W to total load and ratio k of... 

For a given design value of the load effect E, the characteristic values of individual actions G y Q, W. can be expressed using variables x and k as follows... 

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). 

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