basic concept of springs in safe

[farooq]

hi every one, i am confronting some error with the use of safe. i don't understand the basic concept of springs and there application .can some body help me in this metter. i will appreciate any literature or tutorial in this regard.

[igor1234]

The spring in Save is stiffness per unit volume.

Do you want to model soil elasticity and you need a spring value?
What help do you need.

The elementary theory you can find in any finite element book.

[farooq]

igor1234 thankx for replying,
basically i want to design an L shaped combined footing which consists of 4 columns on either sides and a basement retaining wall between the columns. for this problem i have tried to use safe but i am satisfied with the results.
firstly my model is not giving me the punching shear results
secondly the reinforcements it is giving are like reinforcements of slab in the form of column and middle strip.
I am using safe v12.

[AK12]

For reinforcement use the option to design by FEM and not by classical method (strip).

[farooq]

AK12 how will i know that my assumed thickness of the footing or the slab is adequate or not. can u upload a safe model of any footing or a slab.

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HOW will i check the assumed thickness of a slab or a footing to be adequate or not.AK12 can u upload a safe model of a footing or a slab

[engrasad]

Hi farooq ,
Usually thickness of footings is governed by their punching shears. Safe has an option to show you the punching shear ratios. Here you can check the desired ratio. Usually a footing fails in punching if its punching shear ratio is below 1. In that case you've to increase its thickness to increase the ratio above 1. In safe, after running analysis and design of your model, go to Design menu, point to Dispaly Punching Shear Ratios. Now you can consider footings having punching shear ratios below 1 as safe against thickess while those having value greater than 1 should be increased in thickness.
Hope this might help you to some extent.
Regards.

[parhyang]

spring stiffness for analysis of plate on elastic foundations are based on plate load test, graph of pressure vs deflection so it's have units of pressure (e.g kN/m^2) and deflection (e.g m') and this units leads to e.g kN/m^2/m'.

confusions arise when much people says e.g kN/m^3 (volume) ??? please refer to a text book about the basic concept such us from Bowles.