Reversal of Load on Same Face

[NewbieStruct]

I have a condition where there will be stress reversal on a 9' tall CMU Wall on the same (outside) face of wall at storm shelter. Is it more pratical to use each face reinforcing or center reinforcing in this case ? I am confused with the value of 'd' for each face reinforcing when there is reversal of trusses. For each face reinforcing I generally use 5.3" , when stress reverses at the same face will the 'd' become 2"

 

[hokie66]

I assume you are talking about an 8" block. With central reinforcement, you would use the same value of 'd' for both inward and outward pressure, say about 3.5". With bars on each face, your 5.3" number sounds about right.

 

[NewbieStruct]

Sorry, I forgot to mention it is 8" block. So even when stress reverses on the same face 'd' will remain 5.3". One of our engineers says that it will become 2" due to the fact that the stress block will become smaller. I am not understanding his argument.

 

[hokie66]

Well, 'd' for the bars nearest the compression face might be 2", but those bars are normally neglected in flexural calculations. It is the bars on the tension face that are important.

 

[JAE]

With two bars - on each face so to speak - you would have the 5.3" value of d for both directions....assuming you are ignoring the bar on the compression side.

With one bar on one face, you would have a d = 5.3" for loading in one direction and a d = 2" or so for loading in the other direction. Not a good condition to have for reverse loadings.

 

[NewbieStruct]

I am assuming one bar on each face (that is two total bars in one cell). So the 'd' would be 5.3" for both directions.

Thank you all