Safe Iterative Uplift Analysis

[asadishaq]

SAFE perform iterative uplift analysis,any one having experience how to check the results of this analysis???what is the purpose and scope of this analysis???

[WR1]

first of all tell us r u talking about SAFE 8 or 12?

[WR1]

uplift non linear analysis is used so that we get zero tension soil! it can be done by iteration process by manually applying soil springs and removing tension springs...or more easily by program non linear uplift analysis option.

there is a big conceptual difference between safe 8 and 12. i bet most of the guys are still confused to see the difference between 2 programs of same example..

pls continue this topic..im willing to go in details but step by step

[Muhammad Hassan]

Sir Rana waiting for you reply related to conceptual difference between safe 8 and 12.

[WR1]

The main difference between SAFE 8 and 12 is that

SAFE 8: was analysis 2D plate behaviour only

SAFE12: by default it takes full analysis rather than 2D plate

I dont my self aware of the full analysis which SAFE 12 does but the answer to the question that why NON LINEAR UPLIFT analysis in SAFE 8 takes no time and why in 12 it takes hours.

We faced this problem and asked CSI guyz! because personally i dont like the SAFE 8 interface but there were people saying that if you have to do the non linear analysis export it to SAFE 12 which i really dont like.

SAFE 8 was doing only 2D plate analysis (so you dont have to put restraint in x and y) only vertical springs. But in SAFE 12 if you run the analysis and check the log you will find that there is instability error because of no restraint in x and y.

in SAFE 12 the options to select non linear uplift analysis are also very complex. Its not clear to select NON LINEAR UPLIFT in individual load cases or to select the option CONVERT COMBO TO NON LINEAR COMBOS

well dont select the first option to check UPLIFT in each load case (results will be very strange)

rather convert all load combos to non linear for uplift (results will be fine)

but remember here that if you are doing 3d analysis without restraining in x and y your simplest model could take upto 3 hrs to run bcz of instabilities.

to compare the results with SAFE 8 and to save run time goto RUN>Advanced options> and select 2d plate analysis option

so by selecting just option you convert safe 12 to 8. no need to use the older version of SAFE

and also note that in

SAFE 12: Tension is + and Compression is -
SAFE 8: Tension is - and Compression is +

[Ayesha]

SAFE perform iterative uplift analysis,any one having experience how to check the results of this analysis???what is the purpose and scope of this analysis???

This might be helpful. As you have asked how to check the result of the analysis.

SAFE - 10 Foundation Uplift

http://www.csiberkel...arn#page=page-1

Check the attached Seminar notes that I attended. Might help you.

Excerpt from the attached file. (Read 2 following paragraphs)

Iterative for Uplift. When the Analysis Type is Iterative for Uplift, accept the default values for the maximum number of iterations and the convergence tolerance or enter new values by typing them directly in the edit boxes. This option is specifically needed to remove any tension when analyzing mat foundations. Accept the default Maximum Mesh Dimension or enter a new value by typing in the edit box. The Maximum Mesh Dimension is described below.

etabs-concrete-design.pdf

[WR1]

just to add it here that dont chage convergence values. I have tried many types for many many values. They are give stupid results may be im wrong..test it your self

[Badar (BAZ)]

As you all know, that when foundation is subjected to tensile forces,sort of GAP arises at the interface between foundation(excluding pile) and soil.It is because there is no mechanism to transfer tension between two materials and besides both materials cannot take tension.Uplift analysis tries to capture this behaviour.

[asadishaq]

and what about to draw the design strips in safe 12 is it similar to safe 8...which version of safe 12 you are using sir RANA???

[asadishaq]

I am having trouble in drawing of design strips in safe 12 as i am a new user of safe 12...

[WR1]

i am using SAFE 12.3.1 and i think its the latest version

to draw a design strip select the layer A or B and then put the values of start and end of strip widths

For example you want to draw strips of 1m width then click on draw design strips. Select layer A and put 0.5 in all 4 boxes of left start width, left end width, right start width and right end width. This 0.5m or 0.5ft is above and top of center line of design strip so the total width is 1m. Then just replicate this line to cover all your slab.

Similary draw design strips for B layer.

You can draw A layer parallel to X direction and B layer parallel to y direction each 1m width. If you click on "SHOW STRIP WIDTH" in view options dialogue box you can see the widths on screen

Usually it doesnt matter you select column strip or middle stip because you are designing your for unit meter width. So you get reinforcement areas per m. If your strip width is more than 1m then you have to divide the resulting moments or reinforcement areas over that width to get moment per meter or reinforcement per meter.

[WR1]

see these

[m_naeem_b]

Jazakallah. Thankyou very much... For giving us knowledge of drawing strips in SAFE 12

[chasm9a]

Is this procedure only for slab design or footing design or both. I guess it is for both of them.

[rummaan17]

Can someone explain as when to use non-linear allow uplift option for slab design ? Is it only when soil has uplift bearing pressure ?

[asadishaq]

https://www.csiamerica.com/products/safe/watch-and-learn

 

watch the tutorial for SAFE foundations uplift