ACI318-99: Cl.No. 14.3.4 !!!!

[Murali27]

Dear All,

ACI318-1999: Cl.No. 14.3.4

My questions are;

1. Can't we provide 3 layers in 16" wall thick ?

2. Always we do we need to provide the first layer from the exterior surface at 2" distance. Is this applicable in all cases ?

3. Can't we provide 2 layers in 8" or 10" thick wall ?

Thanks,
-Murali27

 

[Taro]

1. Note that Section 14.3 is titled "Minimum reinforcement". You are free to provide more than minimum if you wish.

2. 14.3.4(a) specifies the minimum and maximum distance of the rebar from the wall surface.

3. See 1.

 

[shermanwc]

The code does not prevent you from doing such things, but please note the following:

1. Rebar is most effective for stress and crack control when placed near the concrete surfaces and extremeties of the structural section. Thus, the third layer may not be as effective and may make the wall more conjested for placing concrete.

2. You can provide more than the minimum concrete cover - cover of 3 to 4-inches is used for added corrosion or erosion protection for some structures. However, increased cover can increase crack widths in flexural members.

3. Two layers of steel in an 8" wall makes it extremelyu difficult to properly place and consolidate concrete and is not recommended. Two layers can be used in 10" walls, although still a little "tight".