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.

soft storey
Goto page Previous  1, 2
 
Post new topicReply to topic Thank Post    www.sefindia.org Forum Index -> SEFI Web Site Problems/ Login/Registration Issues
View previous topic :: View next topic  
Author Message
ychodneker
General Sponsor
General Sponsor


Joined: 11 Jan 2010
Posts: 19

PostPosted: Mon Aug 03, 2015 7:04 am    Post subject: Re: SOFT STOREY BUILDING Reply with quote

rajancivildesign wrote:
The column of soft storey meant for car parking  has to be designed for  2.5 times the actual column design moment as per IS 1893-2002 Part 1. Suppose if the building is covered by 3 sides of wall and one side open,  is it mandatory to multiply the column moment by 2.5 times. Experts  kindly comment on this as per codal provision.

V.M.RAJAN.


Dear Rajan Sir,

I think we need to consider the strength of stiffness effects of these 3 sided infill walls (Cl. 7.10.2) and recheck if the storey falls under the definition of a "soft storey".

If we are not considering the effect of infill walls (which we generally don't) then (Cl 7.10.3)

We consider the weight of the infills in the calculation of seismic weight but design the structure as bare frame completely neglecting the in-plane stiffness offered by the infills . Why do we neglect the effect of infills ?
Back to top
View user's profile Send private message
binaya shahi
SEFI Member
SEFI Member


Joined: 03 Jun 2015
Posts: 19

PostPosted: Fri Nov 25, 2016 12:02 pm    Post subject: how to design soft story in etabs? Reply with quote

According to IS code soft story should be design with 2.5 times the base shear.

So, I multiplied the mass source factor by 2.5 in etabs.
but base shear is not increasing twice.
Maybe I should increase the mass source factor until the base shear of soft story building is 2.5 times that of normal building.

I have many questions?
Am I doing it right?
Is my understanding correct.
Is there more appropriate method to do it?
Are columns only structural elements I should separately design for for soft story? or I should design beams and slabs too for soft story.

Please somebody clarify my questions and suggest best way to design building with soft story. and also common errors and misunderstanding regarding such design?
Back to top
View user's profile Send private message
binaya shahi
SEFI Member
SEFI Member


Joined: 03 Jun 2015
Posts: 19

PostPosted: Sat Nov 26, 2016 7:38 pm    Post subject: Reply with quote

I think as mass source in etabs is the earthquake load. multiplying mass source by 2.5  or multiplying earthquake load in load combination should give the same result.

The main problem is that multiplying mass source by 2.5 or earthquake load in load combination by 2.5 in not increasing the base shear much.

To get 2.5 times the base shear, I had to multiply the mass source by 6.
the reinforcement for one of the column for normal analysis was 1200 sq. mm. where as that for the 2.5 times base shear(or 6 times earthquake load) was 6200 sq. mm.

The reinforcement from soft story analysis is more than 5 times that of normal analysis. I want to know whether the difference in reinforcement between two analysis is plausible of not.

for normal case I used the mass source : 1 (dead load), 1(wall load), 1(floor finish), 0.25(live load)

whereas for soft story analysis, i used the mass source: 2.5(dead load), 2.5(wall load), 2.5(floor finish), 0.625(live load)

when I checked the m2 value for the same column in two analysis.
the m2 of the column for soft story analysis was about 3 times the m2 value for normal analysis.

My understanding is that according to IS code the base shear and the moment in beams and columns should be increased by 2.5 times for the soft story analysis.

My doubt is whether I should just use (2.5 times the earthquake load that resulted in not much increase in base shear) or (6 times the earthquake load that resulted in 2.5 times base shear).

Please help me out?
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 Web Site Problems/ Login/Registration Issues All times are GMT
Goto page Previous  1, 2
Page 2 of 2

 

 
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 cannot 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