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9.2.4 Specifications for Nonlinear Calculation
Specifications for Nonlinear Calculation
The nonlinear calculation for the serviceability limit state is prepared in the Serviceability Limit State tab of window 1.1 General Data.
For the design, we select load combinations CO4 to CO6 defined for the serviceability limit state design. In addition, we select the Nonlinear calculation and Activate creep and shrinkage check boxes.
The [Settings for Nonlinear Calculation] button opens the dialog box of the same name. The default settings of the Analysis Method tab remain unchanged. In the Tension Stiffening Effect tab, we specify the following settings.
We select the approach of the Modified steel characteristic diagram. For now we leave the adjustment factor of the tensile strength as 1.00 ⋅ fct. The calculation is performed with the mean axial tensile strength of concrete specified in EN 1992-1-1, table 3.1.
The load duration factor βt is calculated depending on the load cases of the respective load combinations between the limit values 0.25 and 0.4. Specifications for the axial force are of no relevance for pure bending.
We can keep the default values in the Iteration Parameters tab. But we have to adjust the FE division of members with the button.
Finally, we define the settings for creep and shrinkage in window 1.3 Cross-Sections.
The table cell button in column E opens the dialog box for entering the creep and shrinkage parameters.
We change the Type of cement to R and the Effective age to 28 days. The creep coefficient according to EN 1992-1-1 shall be understood as the pure final creep. It usually must still be converted into an effective creep coefficient in accordance with the ratio of creep-producing load to effective load.
The shrinkage is not analyzed further: Due to the almost symmetrical reinforcement in span 1 and the minor reinforcement difference in span 2, the shrinkage curvatures do not significantly contribute to the total deformation. Therefore, we Determine the shrinkage strain as 0.
The input for the nonlinear calculation is now complete. We can start the [Calculation] again.