3 pile, pile cap

[Lytnur]

I’ve noticed engineers design 3 pile, pile caps simplified as a rectangle cap with orthogonal reinforcement how is this justified?

 

[BridgeSmith]

Please post an example detail. I have no idea what the configuration is that you're questioning.

 

[canwesteng]

Same way orthogonal reinforcing is justified in any two way slab or strut and tie model.

 

[Lomarandil]

In markets where labor is expensive, the material savings of a triangular pile cap and rebar layout does not outweigh the extra complexity of building and forming that triangular cap.

 

[HTURKAK]

I’ve noticed engineers design 3 pile, pile caps simplified as a rectangle cap with orthogonal reinforcement how is this justified?

Orthogonal reinf. will not be effective when compared with triangular form. If you write ( pile cap for three piles ) and search the web , one of the outcomes;


Besides main diagonal reinf.Provide minimum orthogonal cage reinf. for all faces .

 

[BridgeSmith]

Ah, now I get what the OP was talking about.

I suppose the reinforcement going directly between the piles would be more efficient in material, but as Lomarandil noted, material cost is only a part of the cost, and in many markets, a small part of the total cost. That balance varies by location and also by when the work was/is done. We have many bridges built 40 or 50 years ago using thin (5/16") steel plates for the webs and vertical stiffeners every 3' or so. Today, that would make the girders twice as expensive as using a 1/2" or 5/8" web and no stiffeners.

 

[dik]

with orthogonal reinforcement how is this justified?

If a slab has the same moment capacity in both orthogonal directions, it has the same moment capacity in all directions.

 

[canwesteng]

In markets where labor is expensive, the material savings of a triangular pile cap and rebar layout does not outweigh the extra complexity of building and forming that triangular cap.

The 3 pile layout is still common though, and rebar is detailed without going diagonally generally.