Difference in reinforcement in etabs and safe

[Ali Khizer]

AoA.

While designing a slab  I have observed that etabs 2016 gives comparatively higher area of steel whereas safe 2016 gives lesser areas. I have made the model in etabs and directly exported the story in safe to design the slab. I have kept the property modifier as 0.25 for slab in bending in etabs. Given the fact that I have exported the file the the section properties and modifers need to be similar in safe as that of etabs.  Can anyone help me why is there such difference in reinforcement for both software?

Here are the models in etabs and safe if it could help.

SAFE.rar

ETABS.rar

[WR1]

1. Because ETABS modifier of 0.25 is different than cracking analysis of SAFE. Are you sure the cracking analysis in SAFE corresponds to 75% cracked section?

2. If you are not performing cracked analysis in SAFE. still results would differ.

[Ali Khizer]

Rana Sir I have not performed cracked analysis. and this is what I want to know why results differ ?? E.g i A n etabs there is almost  3-4 times larger reinforcement values at end as compare to safe. there are also larger value in mid sections but the difference in not that much. A screen shot is attached for your reference. 1st pic is from etabs and 2nd is from safe.  

[WR1]

Please share the bending moment figure also with values shown. Maybe there is difference in material properties between both models?

[Ali Khizer]

Rana Sir the fact I have exported the story data from etabs into safe there need not to be any difference in properties. This mystery is consuming me seriously. For your review I have attached the moment figures of beams from both the models. But I would request you to kindly make a model of your own and see if there is really an issue with it. It would hardly take few minutes for you. Otherwise the model I made are also attached for your review. Thank You.

ETABS2.rar

SAFE2.rar

[WR1]

You are comparing apples to oranges. Your statement that you are not performing cracked analysis is actually NOT TRUE.

On 5/9/2018 at 4:54 PM, Ali Khizer said:

Rana Sir I have not performed cracked analysis.

1. There are stiffness modifiers in ETABS for beams, slabs and columns (in other words, you applied cracking in ETABS).

However, in your SAFE model, there is no cracking analysis performed or stiffness modifiers applied.

2. The self weight of beams or columns (check which one, I don't remember now) is zero in SAFE (again a mismatch). Create a new load case in both let's say "A" and apply 50psf to compare results.

Adjust this and you will get minor but uniform difference between results (in other words, results will be same in ETABS & SAFE).

[Ali Khizer]

Thank you so much Rana Sir. I learned the safe from Youtube tutorials and tried to implement the same. The guy who made the tutorial did the same cracking analysis in Etabs and later on exported the file in safe to design the slab. I too checked out myself at first that the property modifiers which I used in the Etabs were not imported in safe and then I asked one of the guy from industry. He told me that these property modifiers are only for the purpose of analysis not design. but his logic did not strike me that's why I tried to get help from here. I am thankful to you for figuring out this for me.   

[Ali Khizer]

Sir on your remarks I  have corrected all the things. I have not performed the cracked analysis in Etabs and safe. Despite of that it is seen that

1)Safe produces greater reinforcements.

2)there is variation in the steel areas on the locations marked on the attached pics. 

What could be the reason for this?

ETABS3.rar

SAFE3.rar

[WR1]

Difference of 0.2 in² is nothing. You will not get 100% same results. If error is large, check again for dissimilarities.