Default values of concrete materials mechanical properties

[APP]

By creating a new material type 'con_ma' C12/15, the default value of mean concrete strength given by the software is 20MPa. Why is this the case? The nominal strength of the material is 12Mpa but I understand that this is being used for the code-based checks only. What happens with performance-based checks? Which concrete strength value is being used by the software in this case?

[seismosoft]

The material strength required in the nonlinear analyses according to the different standards worldwide is the mean material strength, not the nominal or the characteristic. Which is why you get the 20MPa (nominal+8MPa according to the Eurocode). The performance criteria employ the mean strengths in SeismoStruct and no safety factors, while the code-based checks employ the strengths that are specified by the selected code (usually the nominal) together with the appropriate safety factors.
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