## piled bases - pile loads + forces (springs-pinned)

## piled bases - pile loads + forces (springs-pinned)

(OP)

as has been discussed many times a lot of people model piles as springs in order to spread load as would truly happen. But what restraints do you use in your model to model moments etc? The spring model or one based on rigid (pinned) supports?

## RE: piled bases - pile loads + forces (springs-pinned)

Once the pile configuration is set, you can design the cap use the method for spread footings.

## RE: piled bases - pile loads + forces (springs-pinned)

Hope this clears up any confusion on my query.

## RE: piled bases - pile loads + forces (springs-pinned)

## RE: piled bases - pile loads + forces (springs-pinned)

An aside note, my pile design approach has been to model the foundations as pinned. The reactions that are returned by my analysis are then linked into a seperate pile design program that works on the simple broms method for pile analysis.

## RE: piled bases - pile loads + forces (springs-pinned)

For smaller project with less concern of foundation movement, I too, use pin supports to simplify the design. Actually, I don't think there exists THE CORRECT/INCORRECT way to model/design the foundation system, as long as you have set the loads properly, and taking into account of the subgrade conditions, the system tends to balance itsself, and reach equirbrium ultimately.

Finally, the choice always depends....

## RE: piled bases - pile loads + forces (springs-pinned)

## RE: piled bases - pile loads + forces (springs-pinned)

The pin model, by neglecting the relative movement, in my opinion, is less accurate. However, it has been done over the years by manys, including me. But in order to ensure integrity/longitivity of the foundation system, understanding on behavior of the soil-structural interface, and sound engineering judgement are indispensable.

If you have time to play both, be conservative (but not overly), envelop the maximum if possible. Otherwise, select one method based on the nature of the project, budget and any other constraints, then be consistant throughtout. Your slab will survive if all load case are considered and applied properly. Also important is specify the subgrade preparation properly.

## RE: piled bases - pile loads + forces (springs-pinned)

If it is more complicated, e.g. odd layout, multiple spans e.t.c. then I would expect a full computer analysis would be more accurate.

I would only bother with springs in the latter case.

## RE: piled bases - pile loads + forces (springs-pinned)

## RE: piled bases - pile loads + forces (springs-pinned)

## RE: piled bases - pile loads + forces (springs-pinned)

Take for example a double span beam on three piles. On fixed supports the middle one takes about 62% of the load. Now if these are on springs then the middle support would give more and thus more load would transfer to the outer supports.

Infinitely soft springs would transfer the load equally between the three supports.

## RE: piled bases - pile loads + forces (springs-pinned)