Shearwall flexure reinforcement comparison Etab 9.7.4 vs 16

[FzAh]

 

 

i would like to ask regarding etab shear wall design comparison between etab 9.7.4 and etab 16.

I checked the flexure design of a pier in old version the percentage is 0.81% where as in new version it is 1.77% . Huge difference. Old version of etab shows less reinforcement percentage for flexure compared to new version. Any justification regarding will be highly appreciated.

 

Thanks

[WR1]

Do you really think any reputable software would start giving that much difference in results between different versions? I'd like you to go back and try to understand the shear wall design procedures in help menu and update us what did you find in any case.

If still you have doubts, we are ready to investigate it further.

[FzAh]

There was difference in utilization factor limit. When we are importing older version of etab into new version it is considering utilization factor limit for wall design as default. In older version it was considered as 100% where as in new version after it is imported considering default as 95%. I have updated the utilization factor limit to 100% same as the old version the difference in percentage of reinforcement is reduced. But still it is 6 to 7%.

I have investigated this with my colleagues. There were different feedback like

• Torsional effect are not considered in old version.
• Vc of concrete is reduced in new version
• Axial forces from slabs and beams are considered in new version etc.. 

It will be highly appreciated if someone investigates deep into this, to come to final conclusion.

Thanks.

[israr_sari]

Dears Rana,

One  huge difference even i have noticed, that is short beams failure under earthquake loadings.
short beams that are usually safe in Version 9.7, sometimes  fail in version 16.

This is a common phenomenon in Earthquake analysis. The earthquake shear is either to be multiplied by 2 as per ACI 318-05 or the shear is to be derived from moment capacity at the ends.  The earthquake shear has to be added to the gravity shear resulting in total shear which should not exceed the ultimate shear capacity of the beam (including reinforcement).

 

 

 

 

Edited May 28, 2018 by israr_sari

[WR1]

On 5/27/2018 at 8:52 AM, FzAh said:

There was difference in utilization factor limit. When we are importing older version of etab into new version it is considering utilization factor limit for wall design as default. In older version it was considered as 100% where as in new version after it is imported considering default as 95%.

By default, design utilization is 95% irrespective of which version you are using. Someone might have changed this to 100% in your older model.

On 5/27/2018 at 8:52 AM, FzAh said:

I have investigated this with my colleagues. There were different feedback like

• Torsional effect are not considered in old version.
• Vc of concrete is reduced in new version
• Axial forces from slabs and beams are considered in new version etc.. 

Following link should be in your bookmarks;

https://www.csiamerica.com/products/etabs/releases

I have gone through release notes history and could not find any difference/update to shear wall design for ACI codes in ETABS. If any thing has changed it might be related to code updates and not the version itself.

[WR1]

39 minutes ago, israr_sari said:

This is a common phenomenon in Earthquake analysis. The earthquake shear is either to be multiplied by 2 as per ACI 318-05 or the shear is to be derived from moment capacity at the ends.  The earthquake shear has to be added to the gravity shear resulting in total shear which should not exceed the ultimate shear capacity of the beam (including reinforcement).

What is this related to? Is it the answer to your own question or this what CSI people replied to you?

And yes, the clause you are referring to applies to intermediate moment resisting frames, and that is why you define such beams as spandrels when designing for overstrength factors and for this clause so as not to duplicate 

[FzAh]

Referring to the attached snap shot, beam design output from Etab 16.2.1.

Vu2 = 238.3 ; Vu* = 324.2; Vp= 1791.5587 : Vg= 152.42

Vu2 considered in design is 1943.98 KN (which is addition of Vp (capacity) and Vg (gravity). and shows that the beam fails in shear.

Where in as per code and as said by Mr. Israr it shall be (The earthquake shear is either to be multiplied by 2 as per ACI 318-05 or the shear is to be derived from moment capacity at the ends.  The earthquake shear has to be added to the gravity shear resulting in total shear which should not exceed the ultimate shear capacity of the beam).

Any justification regarding this design results ?

 

[WR1]

You should read the beam design process in ETABS documentation for the desired code. Vp is the shear based on max probable moments at each joint. Vp will be added to gravity shear as ETABS is doing.

[Sardar Ali]

In etab 2016  I have design shear wall and there is difference between area of rebar obtained from display design info and number of rebar shown by run detailing and seeing the sections in detailing and this problem is shown as the graph below clearly also I have attached the etab model file:

 

 

 

TEST P1 Tower .EDB