modulus of elasticity for tempreature effect

[ahmedhegazi]

Hi all
i have a builing 100 Ms lenght with no Expansion Joint, where carrying out tempreature analysis is a must, i carried out the analysis for floor assuming it is restrined by columns above and below , using modulus of elasticity as per ACI , my question is shall i use any reduced value of modulus of elasticity as this tempreature effect will happend on a long time interval?

 

[corus]

What has the time interval got to do with it? Unless your temperatures are approaching 400C I can't see the effects of creep being needed to be considered. You can use temperatrue dependent values of elasticity for steel but for a building I doubt if they'll be significantly diferent from values at room temperature.

corus

 

[ahmedhegazi]

Thanks corus for your reply, but actualy it is and Reincofced concrete Building and i am worried about diffrence between tempreature when concrete will be casted and the service tempreature for the building

 

[shin25]

With time as the concrete strength will grow, the MOE will also increase, until such time when the rate of increase will become negligible. There are different models (CEB-FIP) that can extrapolate this increase.

This effect is carefully considered for post tensioned segmental bridge construction as time dependent behavior is very critical. For reinforced concrete structures, this effect is hardly considered. ACI-318 prediction for E is well enough.

 

[ahmedhegazi]

thanks shin25
but do you think i should use the value mentioned in ACI-318 in slab tempreature analysis or i can make some reduction to it?