When conducting finite element analysis according to the Eurocodes, is it sufficient to use the uncracked moment of inertia, or is there any notion for the effective moment of inertia alike the ACI codes?
Hello,
Very good question.
To my knowledge, ACI is more explicit on this question than EC2.
Indeed, EC2 expressed it in terms of curvature rather effective moment of inertia.
If you conducted a Finite Element Analysis in Static Linear Approach u can use uncracked cross-sectional Area. This is essential due to determining if the analysis under Quasi permanent load case cracked the section or not. If yes and if your goal to find out the deflection u can linearly adjust the deflection results by multiplying them with a modification factor that takes into account creep and shrinkage, of course this is valid for determinant and indeterminate beams as well using one cross section through the beam and by that your results will not be changed at all in bending and shear. Well, When I program solver in linear static analysis I do use inertia of 1 m4 and modulus of Elasticity of 1 GPa, and then modify the section when proceeding in deflection.
Dear George, Modification coefficient can be maintained manually, using Linear Relationships. As you can see this is one of my algorithms I've programmed and u can see the results of the Envelops according to EC-02, the Quasi Permanent deflection combination, is calculated using only EI = 1 (Stiffness), and then When starting to detect the final long term real deflection u can just scale the curve by dividing it by EI, where E is the effective modulus of Elasticity (See Eurocode 02), and I is the cracked or uncracked cross sectional area according to the stress state in the section mentioned.
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