Max Spac in Reinforcemente

[ENGJP22]

Hi guys, I hope everyone is ok, I have this question, I been looking for a
max horizontal spacing between flexural reinforcement, is there any limitation for that? I have a beam with a 40cm width
and the contractor want to use two #8 bars instead of three #6 bars due to availability but I'm not really clear if there is a limitation for bar so far from each other.
Thks in advanced

 

[JedClampett]

I don't know what the code says, but you don't have a problem.

 

[Lomarandil]

I don't have my copy of ACI today, but my notes reference ACI 318-19 24.3.2

I agree that you don't have an issue, particularly for ordinary strengths of concrete/reinforcement and bars inside the beam width. There are some cases where bars spaced too widely in a T-beam flange can require additional consideration for shear flow. But I don't believe you have that.

 

[IDS]

Hmmm.

Bigger bars with wider spacing will have wider flexural cracks. That may not be a problem in some circumstances, but to most design codes in the World it will result in substantially lower allowable stresses for serviceability requirements, which may well be a problem.

Larger crack widths may well also be a problem even if the applicable design code doesn't have any specific crack width requirements.

Doug Jenkins
Interactive Design Services

http://newtonexcelbach.wordpress.com/

 

[bugbus]

Agree with IDS. I think maybe 250 mm is getting to the point where any practical design would start running into crack width issues.

Crack widths aside, I think 300 mm is normally the consensus of the maximum bar spacing, but I don't think any or many codes specifically state this.

 

[IDS]

From Cl. 8.6.1 of Australian Standard AS 3600:

The simplified approach limits bar stress based on bar diameter and/or spacing.


Doug Jenkins
Interactive Design Services

http://newtonexcelbach.wordpress.com/

 

[hokie66]

I would't have a concern with 2-#8 in a 400 wide beam, but if I did, the resulting provision of an extra 20% of bar area would alleviate the concern.