www.sefindia.org

STRUCTURAL ENGINEERING FORUM OF INDIA [SEFI]

 Forum SubscriptionsSubscriptions DigestDigest Preferences   FAQFAQ   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups  RegisterRegister FAQSecurity Tips FAQDonate
 ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log in to websiteLog in to websiteLog in to websiteLog in to forum 
Warning: Make sure you scan the downloaded attachment with updated antivirus tools  before opening them. They may contain viruses.
Use online scanners
here and here to upload downloaded attachment to check for safety.

Response Spectrum Analysis Scale Factor Input in Etabs v2017

 
Post new topicReply to topic Thank Post    www.sefindia.org Forum Index -> SEFI General Discussion
View previous topic :: View next topic  
Author Message
kiranklk
SEFI Regulars
SEFI Regulars


Joined: 26 Dec 2010
Posts: 33
Location: Banglore

PostPosted: Thu May 23, 2019 11:49 am    Post subject: Response Spectrum Analysis Scale Factor Input in Etabs v2017 Reply with quote

Dear Engineers,

     I just observed some changes in response spectrum analysis scale factor in latest Etabs v17, while defining RS function as per IS:1893-2016. You can see in below images as it is asking to input Importance factor(I) & Response Reduction/Ductility(R) value where as it was not there in previous versions of Etabs. While defining RS load cases as shown in below images we are calculating scale factor value as  SF=Ig/2R, but as per new version we need to input scale factor as acceleration(g). Sa/g values are multiplied by (I/2R) by default.

Default SF = (I/2R)= 1.2/10 = 0.12

Acceleration = Z(PGA) x  Default SF = 0.24 x 0.12 = 0.0288


Defined function table in Etabs

Time Period-----Acceleration(Sa/g)
        0        -----       0.0288



1.jpg
 Description:
 Filesize:  240.35 KB
 Viewed:  66 Time(s)

1.jpg



2.jpg
 Description:
 Filesize:  199.56 KB
 Viewed:  72 Time(s)

2.jpg


Back to top
View user's profile Send private message Visit poster's website
Poorna
SEFI Member
SEFI Member


Joined: 31 May 2019
Posts: 2

PostPosted: Fri May 31, 2019 6:14 pm    Post subject: Re: Response Spectrum Analysis Scale Factor Input in Etabs v2017 Reply with quote

Yes, only g is the scale factor.
Back to top
View user's profile Send private message
haridevender
SEFI Regulars
SEFI Regulars


Joined: 25 Mar 2011
Posts: 30

PostPosted: Tue Jun 04, 2019 6:29 am    Post subject: Reply with quote

Hi
After enhancement of base shear, whether SPECX or EQX to be considered for further analysis and design? Code mentioned nothing regarding this.


Thanks and Regards

Hari Devender
Back to top
View user's profile Send private message
Poorna
SEFI Member
SEFI Member


Joined: 31 May 2019
Posts: 2

PostPosted: Tue Jun 04, 2019 1:04 pm    Post subject: Reply with quote

I typically use spectrum cases for the design of elements not static EQ cases as the spectrum considers much better distribution of lateral forces.
But for foundation using spectrum is not recommended as it gives absolute (+ve) values, so for foundations i typically use static EQ.
Back to top
View user's profile Send private message
rojanmathewtsy
General Sponsor
General Sponsor


Joined: 21 Apr 2013
Posts: 29

PostPosted: Thu Jun 06, 2019 7:08 am    Post subject: Reply with quote

haridevender wrote:
Hi
After enhancement of base shear, whether SPECX or EQX to be considered for further analysis and design? Code mentioned nothing regarding this.


Thanks and Regards

Hari Devender


You have to consider both the load cases and takeout the critical out of them for individual members. Because load profile is entirely different in Spectrum case and static case. Simply making equivalent Base shear will not serve the purpose.
Back to top
View user's profile Send private message
haridevender
SEFI Regulars
SEFI Regulars


Joined: 25 Mar 2011
Posts: 30

PostPosted: Thu Jun 06, 2019 10:41 am    Post subject: Reply with quote

Thanks Sir for your reply.
Will you please let me know the literature for which both cases to be considered in analysis and design.

_________________
Hari Devender
Back to top
View user's profile Send private message
rojanmathewtsy
General Sponsor
General Sponsor


Joined: 21 Apr 2013
Posts: 29

PostPosted: Mon Jun 10, 2019 10:21 am    Post subject: Reply with quote

haridevender wrote:
Thanks Sir for your reply.
Will you please let me know the literature for which both cases to be considered in analysis and design.



Actually, Response Spectrum analysis will give you results without any direction or the results will be positive due to modal combinations. So we are using both the methods to do the design. But, I think theoretically, if you are doing a dynamic analysis, then you don't have to follow static analysis. Other experts can shed some light on this.
Note: Response spectrum is not a full fledged dynamic analysis. It is basically static lateral load analysis of individual modes using a design spectra and combining them using proper modal combinations to get peak responses.


Rojan Mathew
Back to top
View user's profile Send private message
Display posts from previous:   
Post new topicReply to topic Thank Post    www.sefindia.org Forum Index -> SEFI General Discussion All times are GMT
Page 1 of 1

 

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum


© 2003, 2008 SEFINDIA, Indian Domain Registration
Publishing or acceptance of an advertisement is neither a guarantee nor endorsement of the advertiser's product or service. advertisement policy