Structural analysis- EC8 reduced moment of inertia

[Anonymous]

Hi, everyone.

I 'm trying to apply reduced moment of inertia according to EC8 par. 4.3.1 (7) to a building model. I have a lot of load cases (additional permanent loads, live loads and seismic load) and I have concluded that the best way to do so is to create a new material with reduced E modulus by half. The question is at what point of the structural analysis do I have to apply this new material, since all static loads should be calculated with the characteristics of uncracked section.

[teixeiranh]

I would say that for ULS use the cracked section properties. For SLS it depends.

[StefanoPasquini6790]

Hi everyone,

My assumption is that the reduced moment of inertia should be applied "only" in seismic cases for uls.

Greetings

[Anonymous]

Hi StefanoPasquini6790,

I totally agree with you, but the problem is that I dont know how to do it in Robot, since if I define a material with a reduced E-modulus, this defintion will be taken into account also in all load cases. Is there any way run static load cases with E-modulus and seismic load cases with a reduced E-modulus?

Thanks in advance

[StefanoPasquini6790]

HI

the answer is "two different models", one for seismic condition and one for standard ULS conditions.

[Anonymous]

Hi,

so you mean that I will create two similar models with members with different E-modulus, get results and design rc members. Hence, I have to combine the two analysis in order to get the most unfavorable reinforcement. Is this the "proper" procedure because even for a small structure this will lead to a massive amount of work?