120m long concrete culvert - shrinkage reinforcement 1

[dohoo]

are these amounts 0.18 percent enough? Even if playing with construction sequencing, pour every other 15 m first then leave it shrink, and then pour the rest in few weeks, the shrinkage is still considerable and I am worried about the cracking... On the other way, as there is a creek running through trying to avoid movement joints. Thanks.

 

[hokie66]

It will crack at 3 to 4 metre centres due to base restraint, and the amount of reinforcement determines the width of the cracks. If you need to have a high degree of shrinkage control as for a water retaining structure, you will need in the order of 0.60 to 0.75 percent reinforcement.

 

[JAE]

And 0.0018 doesn't apply to horizontal reinforcement in walls...per ACI the min. for horizontal steel is 0.002.

 

[JedClampett]

Why not put in a expansion joint at mid span? Over three hundred feet is too long for a continuous member. I would rather put one in then have mother nature put one in for me.
The fact that it is buried will help, and that should let you get away with only one EJ, but normally even 180 ft is a bit long.

 

[hokie66]

Jed,
What's the expansion joint for? The concrete in a culvert won't expand.

 

[dik]

For 120m long culvert, I'd have put 'control' joints at 5m or 6m .o/c or thereabouts and each third joint location would be a proper 'expansion' joint... even though it doesn't expand.

Depending on the use, I'd have increased the hor rfg a tad... maybe to .25% or .3%...

Thanks JAE... didn't know that the % was 0.2% thought it was 0.18...

Dik

 

[JedClampett]

I'd be worried about thermal expansion and contraction, even though it's exposed to soil on the outside.

 

[dohoo]

Thanks guys, decided for two expansion joints, two pours in each part, and will increase the horizontal r/f