Reduction of Moment of Inertia for analysis - How will it affect the design?

[Μηχανικος]

EC8 suggests reducing the moment of inertia to 50% which i did in order to carry out the analysis.

Once the analysis is done and the results are available i export a column for the design in the Provided Reinforcement Module.

Therefore is there any option "In the Provided Reinforcement Module" I need to be aware of, to include or exclude so that the moment of inertia is not further modified by the code options for design?

[Μηχανικος]

There is a an option to consider cracking in the provided reinforcement module. 

I have already reduced the moment of inertia by 50% in order to take the effect of cracking into account, i am not 100% sure but i think this is totally different right? this is for serviceability requirements isnt it? 

[Artur.Kosakowski · Accepted solution]

Hi @Μηχανικος

The option for static analysis of a model is independent from the RC design modules. It will influence only the values of internal forces and you shouldn't make any 'adjustment' due to applying it to a model while calculating reinforcement. 

If you find your post answered press the Accept as Solution button please. This will help other users to find solutions much faster. Thank you.

[Μηχανικος]

I am bit confused right now. This is what i did 

1. for the analysis of the model all sections created have reduced moment of inertia

2. for the design of reinforcement the elements that are already defined in the model (with reduced moment of inertia) have been exported to the provided reinforcement module to calculate the reinforcement.

so the imported elements have a reduced moment of inertia right? do i need to change the moment of inertia back to 100% before i design the reinforcement?

while i am in the column reinforcement module the moment of inertia of the column shown in the sections properties on the left is the reduced value, do i need to change that or it doesnt affect the calculations for reinforcement? 

please see picture below

[Artur.Kosakowski · Accepted solution]

Hi @Μηχανικος

so the imported elements have a reduced moment of inertia right? do i need to change the moment of inertia back to 100% before i design the reinforcement?

Th forces you are about to use for the reinforcement design are taken from a model with the column with reduced moment of inertia but from now on the RC Column module will calculate reinforcement following the code formula for calculations of the moments of inertia (reduced only by cracking and increased due to provided reinforcement when applicable). The data you indicated are only for static analysis of a structure.

If you find your post answered press the Accept as Solution button please. This will help other users to find solutions much faster. Thank you.