Strut & Tie - Calculating Node face dimensions

[astructurale]

Deep Beam Design - One span w/ Cantilever one side only:
When designing a deep beam by strut and tie I'm getting bogged down in determining the appropriate dimensions to apply to the faces of the struts.

In the ACI 318-02 Code Reference example ACI calculates these faces based on the lowest concrete strength of the nodes, struts and ties along with the forces from applied loads, struts and ties.

Starting with a node at a support:
If I know what reinforcing tie width I want to use, and I know what bearing length I have avaliable can't I go about calculating the width of the face of that node (the width of the strut) based on those two factors, and then check that my stresses are not exceeded for any of the three sides?

Subsquently, then can't I use that calculated strut width to find the widths of that strut at the top of my beam? My point load at the top of my beam has no defined bearing lenght either because I'm modeling a distributed load.

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I seem to get stuck in a loop looking at this. Does anyone have an example of a deep beam with a cantilever at one end they can refer me to? I cannot find a worked example, and there are so many possible truss models that could be used.

(I already have a copy of SP-208.)

HELP! I'm so sick of working on this, and I know it should not be this difficult.

 

[kslee2006]

Try Canadian Concrete Code, which is much clear on how to construct S&T model.

 

[astructurale]

Good Idea, I'll see about purchasing one.

 

[UcfSE]

I would guess that as long as you do not exceed your design stress for either the nodes or the struts or ties, and all of your geometry is compatible between the nodes, struts and ties, then it doesn't matter how you get there. Keep in mind that it is an interative process so you may have to work it more than once to get convergence.

 

[astructurale]

UcfSE,

Thanks for confirming that. Going through the iterations to get convergence is a pain if you are new to this. It's easy to get lost in the process.

At least it does appear I am on the right track.