Table 404.1.2(3) & (8)

[jar546]

2009 IRC

What is the difference between these 2 tables other than (8) adds wall heights of 5,6 & 7 feet and it is for more wall thicknesses?

When you look at the same situation for an 8' wall height with 8' of unbalanced backfill you get 2 different answers between Tables 404.1.2(3)&(8)

Anyone know what else I am missing here?

 

[Mule]

Table 404.1.2(3) specifies that the reinforcement shall be in the center of the wall where Table 404.2(8) provides a maximum cover of 1.25 measured from the inside face.

 

[mueller]

Tables 404.1.2 (2), (3) & (4) in column 1 refers to maximun unsuported wall height were table 404.1.2 (8) refers to maximum wall height, without specifing supported or not.

 

[jar546]

Still dont understand the diff between 3 & 8

 

[mueller]

Neither do I now that I read 404 twice. My original thought was that (3) was for walls not laterally supported at the top by the floor system, and (8) was for supported walls. However it doesn’t say that. Not to mention the provisions for a foundation wall to be considered laterally supported (06- 404.1) have been deleted. Now I just noticed table (8) does not even say it’s for concrete walls it only says flat basement walls. All the other tables say concrete, waffle grid or screen grid.

Gunna have to read it again!

 

[jar546]

Got, it, understand now. Thanks. There are some changes and errata on Pg 98. After seeing the changes, it makes sense.

 

[peach]

(8) is a busier table... puts more information in one place.

Now, Jeff, I am going to log off.. walk the dogs and try to log in later... whatever girl scout "cookie" thing you did may have worked..

Later,

Cindy

 

[jar546]

Table (3) is for when the placement of the vertical rebar is in the center or towards the center of the concrete thickness

Table (8) is for when the placement of the vertical rebar is toward the interior face of the concrete wall with a maximum thickness of 1-1/4" from the face of the inside.

Apparently when you place the rebar near the face of the concrete it is stronger therefore the requirements are less than that of Table (3)

I don't think the extra time getting the rebar placed is worth what you will save in rebar

Make sure you guys make the changes to page 98

 

[peach]

it looks like a one size fits all table... the vertical steel always needs to be on the tension side of the wall.. go way back in the AISI standards.. it's always been in there for reinforcing steel... well maybe not always... for as long as I've been in this business, anyway. Concrete doesn't take tension very well (inside wall)... you can compress it alot before it fails.. but you can't put it into tension before it snaps..

That's why the soils are important and the amount of backfill is important.. in addition to wall thickness

 

[RJJ]

I need to find the errata! That being said the tables give a number of ways to design a wall. As peach referenced the soil is the issue. Not just the soil that is supporting the walls, but if soil is being imported to fill the wall. One can make assume the soil on site is correct for the design when the soil is imported. This the tricky part! Very often soil with different condition could be used that over time could cause a failure. So the job doesn't end with the approval of the wall design. One must check the soil being placed the creates the unequal back fill.JMHO!