| 5.7 (105)
| Nonlinear analysis
When using nonlinear analysis the following assumptions are allowed:
— For reinforcing steel diagram «stress — deformation» based on figure 3.8 (curve A) is used, where instead of values f yk and kf yk in this diagram values 1.1 fyk and 1.1 kf y should be used;
— For pre-stressed steel idealized diagram «stress — deformation», given in clause 3.3.6 (figure 3.10, curve A) is used, where in this diagram instead of value fpk value 1,1 fpk;should be used;
— For concrete diagram «stress — deformation» based on formula (3.14) in clause 3.1.5 is used, where in this formula as well as for value k, instead of value fcm index g cffck, should be used, where g cf = 1,1g S /g C.
The following project format should be used:
— Make estimate of resistance for different levels of corresponding effects which have to be raised starting from values of serviceability. Such rise should be performed in the form of incremental steps, and in such a way that values g GGk and g QQk were obtained at one and the same step. Incrementation process should continue until one of structure sections reaches strength limit calculated accounting for value a cc , or complete structure destruction is achieved. Corresponding load is designated qud;
— having applied overall coefficient of margin of safety g O, obtain corresponding strength 
— Make sure one of the following nonequalities is observed:
 , (5.102 aN)
 , (5.102 bN)
 , (5.102 cN)
where g Rd — partial coefficient of model uncertainty for resistance, g Rd = 1,06;
g Sd — partial coefficient of model uncertainty for effect, g Sd = 1,15;
g O — overall coefficient of margin of safety, g O = 1,20.
For details see Annex PP.
If characteristics of model uncertainty g Rd and g Sd in the course of analysis are explicitly not accounted for (i.e., it is assumed that g Rd = g Sd = 1), then value g O = 1,27 should be used
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