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.

Difference between Buckling and P-Delta analysis.
Goto page Previous  1, 2, 3
 
Post new topicReply to topic Thank Post    www.sefindia.org Forum Index -> Er. T. Rangarajan
View previous topic :: View next topic  
Author Message
thirumalaichettiar
Silver Sponsor
Silver Sponsor


Joined: 26 Jan 2003
Posts: 3544

PostPosted: Wed Oct 31, 2012 11:11 pm    Post subject: Reply with quote

More information on BUCKLING:

Link to view images of buckling of various elements –plates,beams, columns etc.

https://www.google.co.in/search?q=buckling+of+plates&hl=en&biw=1280&bih=612&prmd=imvns&tbm=isch&tbs=simg:CAESEgn5QX7nIqkh5SEyDZtz9wowLA&dur=8534

Attached a PDF file explaining in simple term about BUCKLING and more.

T.RangaRajan.



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.
Buckling Sefi.pdf
 Description:

Download
 Filename:  Buckling Sefi.pdf
 Filesize:  89.4 KB
 Downloaded:  1637 Time(s)

Back to top
View user's profile Send private message
thirumalaichettiar
Silver Sponsor
Silver Sponsor


Joined: 26 Jan 2003
Posts: 3544

PostPosted: Wed Oct 31, 2012 11:25 pm    Post subject: Reply with quote

I will be adding more information on P-Delta in the next postings and also w.r.t STAADPRO .

Hope the information posted in my previous postings are sufficient to understand BUCKLING which is an instability problem for all types of elements in a structure.

While P delta is not related to plates, shell elements.


P-Delta effects are calculated for frame members only. They are not calculated for finite elements or solid elements. P-Delta and Nonlinear analysis is restricted to structures where members carry the axial load from one structure level to the next.

NOTE:

Any comments good or bad is welcome since Bad comments will encourage to improve but good one will accelerate to add more interesting topics.

T.RangaRajan.
Back to top
View user's profile Send private message
tsriharivaishu
SEFI Member
SEFI Member


Joined: 28 Oct 2011
Posts: 8

PostPosted: Thu Nov 01, 2012 6:42 am    Post subject: Difference between Buckling and P-Delta analysis. Reply with quote

Dear all,We are designing one bridge for msw transfer station.can u pls suggest me what class of loading(as per IRC) should I consider for max weight of vehicle is 40 MT including its own weight.Regards Sent from BlackBerry® on Airtel
From: "vikram.jeet" <forum@sefindia.org>
Date: Wed, 31 Oct 2012 11:07:05 +0530
To: <general@sefindia.org>
ReplyTo: general@sefindia.org
Subject: [SEFI] Re: Difference between Buckling and P-Delta analysis.

     Dear Rangarajan sir is not satisfied so far , and rightly so since both the effects  have a thin lining segregating them . Dr NS sir who always provide his expert opinion  is currently in India, may not be logging sefi regularly.Let us await his version - - -   In nut shell it seems that - -   P-Delta Effect - - - P *Delta (of Joint displacement due to sway)   Buckling - - - P *Delta (of member deflection along its length)    P - - Axial load   best regds   vikramjeet -- ­­         --

Posted via Email
Back to top
View user's profile Send private message
rahul.leslie
General Sponsor
General Sponsor


Joined: 01 Apr 2008
Posts: 493
Location: Trivandrum

PostPosted: Fri Nov 02, 2012 10:59 am    Post subject: Reply with quote

Dear SEFIans,

   The sum and substance of what I wished to say has already been explained by my peers Ananthan, Bhathena & Shanmugasundaram. I shall add a few points to those above, but presented as if from scratch.

From a purely computer analysis point of view:

   1) Linear Buckling Analysis: This is technically an eigen value extraction analysis. In practice what you do is; you run a loaded Finite Element model (in STAAD or ANSYS) which then returns a ‘load factor’ for each mode (ie., each pattern or deflected shape for failure), showing how much towards buckling the structure is. If the factor is grater than 1, it means the structure is safe (in that mode). Higher the value, the safer it is. If less than one, it means the structurehas buckled.

   This is fundamentally related to the procedure where we use the euler-rankine approach of proceeding from its l/r ratio, but that the latter is member wise deermination, and not a global behavior approach.

2) P-Delta (P-D, not P-d) analysis: This is a sort of multiple re-analysis method, as explained by Bhathena

Quote:
If you load this pipe with say 1000kg. An axial force of 1000kg is produced and a bending moment of 1000 x 0.006 = 6 kg.m. The force also produces a deflection d1. So now the eccentricity is 6mm. + d1. This produces another set of calculations. About 3-4 iterations will stabilize the forces. At that time the original 6mm. would have become 6+d1+d2+d3...dn.


In effect, the geometry (internally, the stiffness matrix) is modified each time the analysis is re-run.

3) Geometric Non-Linear analysis: It is all of the P-D analysis, plus updating the stiffness change of each element due to ‘stress stiffening effect’ also. This is because stiffness of elements change when stresses – like stiffness of a guitar string increases when tensioned (that’s why the pitch gets higher), with no change in young’s modulus or cross section.  The analysis is done in multiple steps, with load applied in increments until total load is reached.

4) Non-linear Buckling analysis – this is again, same as the Geometric Non-Linear analysis, but the analysis continued, with load applied in increments, not until total load is reached, but until any of the elements fails in buckling. This is because elements (like columns, for example) actually lose stiffness when compressed (and likewise gains stiffness if subjected to tension). As the analysis progresses, at that point when any of (or a couple of) the elements loses stiffness to such an extend that it can no longer support the loads coming on it, the buckling point has been reached, and the analysis ends (actually the program aborts – older ones hang). Then you can see which all failed, and at what load they failed.
  
Having said all these, the terminology of these is still a matter of confusion to me – namely, they are (a) P-Delta analysis, (b) Geometric Non-Linear analysis and (3) Geometric Non-Linearity with stress stiffening. They are terms I read from different packages (STAAD and ANSYS). I guess either (a) and (b) are the same, or (b) and (c) are the same. For the above write up, I’ve assumed the latter to be the case, but I’m not sure. I request the senior SEFIans’ to clarify this for me

I wish this discussion would continue with contributions from others.

Regards,
Rahul Leslie
Back to top
View user's profile Send private message Visit poster's website
rahul.leslie
General Sponsor
General Sponsor


Joined: 01 Apr 2008
Posts: 493
Location: Trivandrum

PostPosted: Fri Nov 02, 2012 5:32 pm    Post subject: Reply with quote

Please bear with me... concerning my last (above) posting, there were mistakes on the first go, which I later corrected (by editing the posting). Sorry...

Rahul Leslie
Back to top
View user's profile Send private message Visit poster's website
thirumalaichettiar
Silver Sponsor
Silver Sponsor


Joined: 26 Jan 2003
Posts: 3544

PostPosted: Fri Nov 02, 2012 11:42 pm    Post subject: Reply with quote

Hope that Engineers,Rahul and Ananthansemban are discussing the P Delta and Buckling based on STAADPRO software and from its manual.

Reference to Er.Rahul's comment on Buckling I add a PDF about the Buckling Factor since I can not put it in this page .

It gives some guidance.

T.RangaRajan



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.
Sefi Buckling.pdf
 Description:

Download
 Filename:  Sefi Buckling.pdf
 Filesize:  76.72 KB
 Downloaded:  7542 Time(s)



Last edited by thirumalaichettiar on Wed Nov 07, 2012 4:01 pm; edited 1 time in total
Back to top
View user's profile Send private message
Vishal
...
...


Joined: 06 Aug 2008
Posts: 124

PostPosted: Wed Nov 07, 2012 8:20 am    Post subject: Reply with quote

Dear Rengarajan Sir,

In the pdf you uploaded, the table is truncated towards the end.Can you please upload it again?

Thanks
Back to top
View user's profile Send private message
thirumalaichettiar
Silver Sponsor
Silver Sponsor


Joined: 26 Jan 2003
Posts: 3544

PostPosted: Wed Nov 07, 2012 4:02 pm    Post subject: Reply with quote

Er.Vishal,

Check now!

T.RangaRajan.
Back to top
View user's profile Send private message
thirumalaichettiar
Silver Sponsor
Silver Sponsor


Joined: 26 Jan 2003
Posts: 3544

PostPosted: Sat Nov 10, 2012 3:07 pm    Post subject: Reply with quote

P-DELTA IN STAAD:

Collection of the notes from the Help menu of STAAD PRO is attached. This is in response of Er.Rahul's posting in the link:
http://www.sefindia.org/forum/viewtopic.php?t=13080

In the abstract the important points are marked in BOLD and RED colour.

May be useful for those using STAADPRO.

T.RangaRajan.



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.
PDELTA & BUCKLING1.pdf
 Description:

Download
 Filename:  PDELTA & BUCKLING1.pdf
 Filesize:  185.97 KB
 Downloaded:  4961 Time(s)

Back to top
View user's profile Send private message
Vishal
...
...


Joined: 06 Aug 2008
Posts: 124

PostPosted: Tue Nov 13, 2012 10:26 am    Post subject: Reply with quote

Quote:

Er.Vishal,

Check now!


Thanks Sir
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 -> Er. T. Rangarajan All times are GMT
Goto page Previous  1, 2, 3
Page 3 of 3

 

 
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