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.

IS:801 -1975 - Design of Cold formed Sections
Goto page 1, 2  Next
 
Post new topicReply to topic Thank Post    www.sefindia.org Forum Index -> SEFI General Discussion
View previous topic :: View next topic  
Author Message
chellappan_str
SEFI Member
SEFI Member


Joined: 13 Nov 2009
Posts: 5

PostPosted: Sun May 27, 2018 8:06 pm    Post subject: IS:801 -1975 - Design of Cold formed Sections Reply with quote

Dear Sir,
Greetings from Chellappan Annamalai to each and every member of Sefians,


I would like to know when the IS:801-1975 is going to get updated?
I need some clarifications on design of cold formed sections as per the following.

1) We are designing the solar structure using Euro codes to check the Lateral buckling of thin gauge sections and as per the market since the IS:801 is not revised and there is no provision to check the lateral buckling but the Indian solar market designs are not checked for lateral buckling, most of the tenders are specified to use Indian Code in that case there is no provision to check the lateral buckling and there is lot of differences in terms of section sizes compare to staad design using IS: 801 and special software to use euro code, the stress ratios are 50% in IS:801 where as in Euro code it is 99% due to lateral buckling check. My question to the team here is when the IS: 801 is going to get revised and updated based on the International codes if not , the code should be withdrawn to safe guard of the structures.

2) In staad there is no provision to check the effective length of top flange and bottom flange separately , for example in PEB building main frame design we used to keep the flange brace at the same purlin location, in that case when the nodes are created in staad to use the purlin loads and keep the common effective length of top and bottom flange. In solar structures the purlins are connected to the rafter in the top flange and the bottom flange is free but actual effective length should be taken the full length of the rafter but none of them are not considering. either the software should be revised to keep the provision for top flange effective length and the bottom flange effective length. need your views on this.

3) As per IS: 875 -Part-3 - 2015 ,for a mono sloped structures the CG of pressure should act as 0.3 W , W is the width of the solar structures, that means the load should be applied as uniformly varying load and not uniform loads. if we apply the uniform loads ( 0.5W) then the moment at the column is very less and when we compare the UVL load and UDL load the moment are vaying 50% more, there is no proper guidance to use IS:875-part-3 and solar Industry is doing on its own with out any control of the design basics. Need your views on this

4) The solar structures are supported by a single column in that case as per the end condition that is one end fixed and other end free end then the effective length should be 2L and none of the solar structures are not designed for that. This is against the principle of Strong Column & Weak Beam. Need your views on this.

5) Is there any guidance to design solar structures? at present building codes are used to design and the uplift forces are predominant and that too very less of 1.4T , in that case the supporting pile is it required to go with M20 concrete why cant be M15 or lesser? the compression forces are very much lesser say 1T. Need your views on this.

6) In IS:801-1975 the code clearly says to check combined bending and shear, the formulas are applicable only for single web sections that is C, Z, only and when we use HAT sections and U sections there will be double web in that case there is no provision in the code, how to design? at present we are using a special software as per euro code the hat sections can be designed but some times tender says the design should be based on IS:801 - 1975. Need your views on this.

7) Is there any committee is formed to revise the IS: 801 and also what kind of help/ guidelines can be given to the solar community to design the structures, due to the price pressures nowadays the tonnage for the Megawatt is shrinking down to 18T/MWp this is not a healthy design practices. Need your thought and help.

8) Importance of panel braces and diagonal braces , as per IS-800-2007  clause 3.9.3 Wind and earthquake forces are reversible and
therefore call for rigidity and strength under force
reversal in both longitudinal and transverse directions.
To resist torsional effects of wind and earthquake
forces, bracings in plan should be provided and
integrally connected with the longitudinal and
transverse bracings, to impart adequate torsional
resistance to the structure.  at present the solar Industry is ignoring the condition will leads to solar glass panel will get a crack, Need your views on this.

9) Lateral buckling is not depending on the strength of the material it is purely based on the sections sizes, as per IS:801 -1975 it is working stress method and also compare to euro codes where the load should be factored and checked for lateral buckling the effects are different. need your views.

Note: This is really a helpful topic to the Solar Industry to design the structure in a right way. Kindly help us.

- Thanks & Regards
Chellappan Annamalai
Back to top
View user's profile Send private message
Rudra Nevatia
...
...


Joined: 26 Jan 2003
Posts: 202
Location: Mumbai

PostPosted: Mon May 28, 2018 12:30 pm    Post subject: IS:801 -1975 - Design of Cold formed Sections Reply with quote

Hi


Just about finished a Google workbook for solar mounting structure. You can access it at the following link. Do give it try.


https://docs.google.com/spreadsheets/d/165hweOq2q0mZgGkhzyWQYwmFncPqZ9jk4BSTVechHKM/edit?usp=drivesdk


Regards,
Rudra Nevatia

On Mon, May 28, 2018, 2:12 PM chellappan_str <forum@sefindia.org (forum@sefindia.org)> wrote:

Quote:
Dear Sir,
Greetings from Chellappan Annamalai to each and every member of Sefians,


I would like to know when the IS:801-1975 is going to get updated?
I need some clarifications on design of cold formed sections as per the following.

1) We are designing the solar structure using Euro codes to check the Lateral buckling of thin gauge sections and as per the market since the IS:801 is not revised and there is no provision to check the lateral buckling but the Indian solar market designs are not checked for lateral buckling, most of the tenders are specified to use Indian Code in that case there is no provision to check the lateral buckling and there is lot of differences in terms of section sizes compare to staad design using IS: 801 and special software to use euro code, the stress ratios are 50% in IS:801 where as in Euro code it is 99% due to lateral buckling check. My question to the team here is when the IS: 801 is going to get revised and updated based on the International codes if not , the code should be withdrawn to safe guard of the structures.

2) In staad there is no provision to check the effective length of top flange and bottom flange separately , for example in PEB building main frame design we used to keep the flange brace at the same purlin location, in that case when the nodes are created in staad to use the purlin loads and keep the common effective length of top and bottom flange. In solar structures the purlins are connected to the rafter in the top flange and the bottom flange is free but actual effective length should be taken the full length of the rafter but none of them are not considering. either the software should be revised to keep the provision for top flange effective length and the bottom flange effective length. need your views on this.

3) As per IS: 875 -Part-3 - 2015 ,for a mono sloped structures the CG of pressure should act as 0.3 W , W is the width of the solar structures, that means the load should be applied as uniformly varying load and not uniform loads. if we apply the uniform loads ( 0.5W) then the moment at the column is very less and when we compare the UVL load and UDL load the moment are vaying 50% more, there is no proper guidance to use IS:875-part-3 and solar Industry is doing on its own with out any control of the design basics. Need your views on this

4) The solar structures are supported by a single column in that case as per the end condition that is one end fixed and other end free end then the effective length should be 2L and none of the solar structures are not designed for that. This is against the principle of Strong Column & Weak Beam. Need your views on this.

5) Is there any guidance to design solar structures? at present building codes are used to design and the uplift forces are predominant and that too very less of 1.4T , in that case the supporting pile is it required to go with M20 concrete why cant be M15 or lesser? the compression forces are very much lesser say 1T. Need your views on this.

6) In IS:801-1975 the code clearly says to check combined bending and shear, the formulas are applicable only for single web sections that is C, Z, only and when we use HAT sections and U sections there will be double web in that case there is no provision in the code, how to design? at present we are using a special software as per euro code the hat sections can be designed but some times tender says the design should be based on IS:801 - 1975. Need your views on this.

7) Is there any committee is formed to revise the IS: 801 and also what kind of help/ guidelines can be given to the solar community to design the structures, due to the price pressures nowadays the tonnage for the Megawatt is shrinking down to 18T/MWp this is not a healthy design practices. Need your thought and help.

Cool Importance of panel braces and diagonal braces , as per IS-800-2007† clause 3.9.3 Wind and earthquake forces are reversible and
therefore call for rigidity and strength under force
reversal in both longitudinal and transverse directions.
To resist torsional effects of wind and earthquake
forces, bracings in plan should be provided and
integrally connected with the longitudinal and
transverse bracings, to impart adequate torsional
resistance to the structure.† at present the solar Industry is ignoring the condition will leads to solar glass panel will get a crack, Need your views on this.

9) Lateral buckling is not depending on the strength of the material it is purely based on the sections sizes, as per IS:801 -1975 it is working stress method and also compare to euro codes where the load should be factored and checked for lateral buckling the effects are different. need your views.

Note: This is really a helpful topic to the Solar Industry to design the structure in a right way. Kindly help us.

- Thanks & Regards
Chellappan Annamalai








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


Joined: 26 Jan 2003
Posts: 68

PostPosted: Mon May 28, 2018 3:02 pm    Post subject: Reply with quote

Dear Mr Chellappan

The new IS:801 will be coming up in Limit state format which will be primarily using the direct strength method and the effective width method as an another option.  All I can say is that code will come shortly.

(1) Oh my dear friend, IS:801 has provisions for LTB. One of the best provision in fact with moment modification factors Cb.  Please read the code well. I encourage you take some help to understand the LTB provisions. Clause 6.3 in IS:801 is for unbraced frames or in other words beams undergoing LTB.

(2) I am not going to answer this question as it is something to do with STADD.  I dont use STADD for cold formed steel design.

(3) (4) and (5) has already been discussed in this forum on various contexts.

(6) IS:801 is adequate for design of Hats and U sections.  All you need to do is to identify stiffened elements and unstiffened elements in a cross section and ascertain whether they are subjected to axial or bending compression. Design the effective section accordingly.

(7) Yes there is a BIS Sub committee working on IS:801. The code will enable the design of all members and systems.  There is nothing special about solar structures. Surely the clauses will enable a good designer to come out with optimum yet rational design.

(Cool These provisions are basically for buildings.  Extension of these to other structures need careful judgement. Please check whether you get a primary torsion in a solar supporting structures.

(9) LTB provisions and distortion buckling provisions of EC3 is highly complicated.  Of course the future IS:801 will be in limit state format.

regards
arul Jayachandran IIT Madras
Back to top
View user's profile Send private message
Rudra Nevatia
...
...


Joined: 26 Jan 2003
Posts: 202
Location: Mumbai

PostPosted: Mon May 28, 2018 5:30 pm    Post subject: IS:801 -1975 - Design of Cold formed Sections Reply with quote

Solar PV Mounting Structure Stability†
https://www.linkedin.com/pulse/solar-pv-mounting-structure-stability-rudra-nevatia


Regards
Rudra Nevatia

Posted via Email
Back to top
View user's profile Send private message
Rudra Nevatia
...
...


Joined: 26 Jan 2003
Posts: 202
Location: Mumbai

PostPosted: Mon May 28, 2018 5:30 pm    Post subject: IS:801 -1975 - Design of Cold formed Sections Reply with quote

Per my understanding, IS 801 does not cover distortional buckling and local buckling under stress gradient. This can lead to unsafe design.


Regards
Rudra Nevatia

On May 28, 2018 10:32 PM, "arulsteel" <forum@sefindia.org (forum@sefindia.org)> wrote:
Quote:
Dear Mr Chellappan

†The new IS:801 will be coming up in Limit state format which will be primarily using the direct strength method and the effective width method as an another option.† All I can say is that code will come shortly.

(1) Oh my dear friend, IS:801 has provisions for LTB. One of the best provision in fact with moment modification factors Cb.† Please read the code well. I encourage you take some help to understand the LTB provisions. Clause 6.3 in IS:801 is for unbraced frames or in other words beams undergoing LTB.

(2) I am not going to answer this question as it is something to do with STADD.† I dont use STADD for cold formed steel design.

(3) (4) and (5) has already been discussed in this forum on various contexts.

(6) IS:801 is adequate for design of Hats and U sections.† All you need to do is to identify stiffened elements and unstiffened elements in a cross section and ascertain whether they are subjected to axial or bending compression. Design the effective section accordingly.

(7) Yes there is a BIS Sub committee working on IS:801. The code will enable the design of all members and systems.† There is nothing special about solar structures. Surely the clauses will enable a good designer to come out with optimum yet rational design.

(Cool These provisions are basically for buildings.† Extension of these to other structures need careful judgement. Please check whether you get a primary torsion in a solar supporting structures.

(9) LTB provisions and distortion buckling provisions of EC3 is highly complicated.† Of course the future IS:801 will be in limit state format.

regards
arul Jayachandran IIT Madras








Posted via Email
Back to top
View user's profile Send private message
kantishc
SEFI Member
SEFI Member


Joined: 14 Oct 2009
Posts: 2

PostPosted: Mon May 28, 2018 5:30 pm    Post subject: IS:801 -1975 - Design of Cold formed Sections Reply with quote

Thanks Dr. Arul Jayachandran for such valuable information.





On Mon, May 28, 2018 at 8:32 PM, arulsteel <forum@sefindia.org (forum@sefindia.org)> wrote:
Quote:
           Dear Mr Chellappan

The new IS:801 will be coming up in Limit state format which will be primarily using the direct strength method and the effective width method as an another option. All I can say is that code will come shortly.

(1) Oh my dear friend, IS:801 has provisions for LTB. One of the best provision in fact with moment modification factors Cb. Please read the code well. I encourage you take some help to understand the LTB provisions. Clause 6.3 in IS:801 is for unbraced frames or in other words beams undergoing LTB.

(2) I am not going to answer this question as it is something to do with STADD. I dont use STADD for cold formed steel design.

(3) (4) and (5) has already been discussed in this forum on various contexts.

(6) IS:801 is adequate for design of Hats and U sections. All you need to do is to identify stiffened elements and unstiffened elements in a cross section and ascertain whether they are subjected to axial or bending compression. Design the effective section accordingly.

(7) Yes there is a BIS Sub committee working on IS:801. The code will enable the design of all members and systems. There is nothing special about solar structures. Surely the clauses will enable a good designer to come out with optimum yet rational design.

( These provisions are basically for buildings. Extension of these to other structures need careful judgement. Please check whether you get a primary torsion in a solar supporting structures.

(9) LTB provisions and distortion buckling provisions of EC3 is highly complicated. Of course the future IS:801 will be in limit state format.

regards
arul Jayachandran IIT Madras
     



     


Posted via Email
Back to top
View user's profile Send private message
kantishc
SEFI Member
SEFI Member


Joined: 14 Oct 2009
Posts: 2

PostPosted: Mon May 28, 2018 5:30 pm    Post subject: IS:801 -1975 - Design of Cold formed Sections Reply with quote

Thanks Dr. Arul Jayachandran for such valuable information.





On Mon, May 28, 2018 at 8:32 PM, arulsteel <forum@sefindia.org (forum@sefindia.org)> wrote:
Quote:
           Dear Mr Chellappan

The new IS:801 will be coming up in Limit state format which will be primarily using the direct strength method and the effective width method as an another option. All I can say is that code will come shortly.

(1) Oh my dear friend, IS:801 has provisions for LTB. One of the best provision in fact with moment modification factors Cb. Please read the code well. I encourage you take some help to understand the LTB provisions. Clause 6.3 in IS:801 is for unbraced frames or in other words beams undergoing LTB.

(2) I am not going to answer this question as it is something to do with STADD. I dont use STADD for cold formed steel design.

(3) (4) and (5) has already been discussed in this forum on various contexts.

(6) IS:801 is adequate for design of Hats and U sections. All you need to do is to identify stiffened elements and unstiffened elements in a cross section and ascertain whether they are subjected to axial or bending compression. Design the effective section accordingly.

(7) Yes there is a BIS Sub committee working on IS:801. The code will enable the design of all members and systems. There is nothing special about solar structures. Surely the clauses will enable a good designer to come out with optimum yet rational design.

( These provisions are basically for buildings. Extension of these to other structures need careful judgement. Please check whether you get a primary torsion in a solar supporting structures.

(9) LTB provisions and distortion buckling provisions of EC3 is highly complicated. Of course the future IS:801 will be in limit state format.

regards
arul Jayachandran IIT Madras
     



     


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


Joined: 26 Jan 2003
Posts: 68

PostPosted: Tue May 29, 2018 5:41 am    Post subject: Reply with quote

Dear Rudraji

Yes you are very right. It neither deals with Distortional buckling (DB) nor elements under moment gradient.  DB became a limit state of design recently after the new generation steels with 550 MPa YS and cold reduced steels which have US/YS ratio around 1.05.

We are trying to derive a simple distortional buckling equations for Indian designers.  PFA a paper by us in the International Journal of Thinwalled structures.  We are proposing to the BIS committee.

regards
arul IITM



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.
TWS DB paper.pdf
 Description:
DB predictions for IS:801

Download
 Filename:  TWS DB paper.pdf
 Filesize:  675.33 KB
 Downloaded:  146 Time(s)

Back to top
View user's profile Send private message
chellappan_str
SEFI Member
SEFI Member


Joined: 13 Nov 2009
Posts: 5

PostPosted: Tue May 29, 2018 2:08 pm    Post subject: Reply with quote

Dear Arul Jayachandran
Dear Rudhra Nevatia,
Thanks for your expert views, for lateraly un braced beam c section with lip & Hat sections.

The top flange is connected to the purlin at a distance of 1.3 m and similarly 4purlins are connected at top flange of C section rafter and bottom
flange is not linked with any  of the member and overall
Length is 3.3m in that case the Un supported length of the top flange is 1.3m and bottom flange will be 3.3m. Now tell me how to use the formula. If I use unsupported length as1.3m then bottom flange is free to rotate.
Due to availability of high strength material of 550MPA with thin guage sections of 1.2mm and lesser,  the effective length of bottom flange really a concern.
Similarly for a hat section of 0.7mm thk. Purlin top flange will be 1m bottom flange will be the bay spacing as 4m.
Need your expert view.
-Thanks & Regards
Chellappan Annamalai
Back to top
View user's profile Send private message
ALEX IMMANUEL THAINESE
SEFI Regulars
SEFI Regulars


Joined: 11 Jun 2012
Posts: 30

PostPosted: Wed May 30, 2018 5:30 am    Post subject: Reply with quote

I think your purlin is hat section ... am I right ??


Your description of section is little confusing ? Correct me if you are wrong


Considering the rafter to be c section with lip ,  and bracing to be discrete at 1.3 m at top and full span at bottom

Now if you refer most of the books , singly symmetric COld form section are not check for top and bottom  flange of the rafter , unlike for built up I profiles which is checked because you can use different cross section  size and

But here you may have to totally changed you section if required to be revised .

So the correct logic is to use the max unbraced length value for flexure checks  , which is 3 m   Not 1.5 m and it is not required to check top and bottom flange separately as you can understand you canít modify only botttom flange or top flange separately

But if you can provide flange brace at all purlin location then you can take 1.3 m
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
Goto page 1, 2  Next
Page 1 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 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