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problem in optimization on staad pro

 
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rahul_sharma1987
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Joined: 09 May 2012
Posts: 8

PostPosted: Thu May 17, 2012 2:28 pm    Post subject: problem in optimization on staad pro Reply with quote

Hello friends i am designing a pre engineered building on staaad pro.I am facing lots of problem like the rafters are failing in combined axial compression and bending(section7.1.1 IS 800 1983). I try to optimized it but it doent work the unity ratio is not
going below 1.7 and the size of rafter increased too much. Can anyone tell me some trick or some easy way to otimize my structure so that the structure doesnt fail and light weight also.
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TBSPL_6
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Joined: 17 Jan 2009
Posts: 28

PostPosted: Thu May 17, 2012 6:10 pm    Post subject: Re: problem in optimization on staad pro Reply with quote

HI RAHUL

IST OF ALL , U PLZ  GO THROUGH YOURSELF , IN THE PRIMARY ANALYSIS PART ,

AND CHECK THE  DL, LL CL ,CRN L ETC PROPERLY APLIED , THAT AT REQUIRED  PORTION ONLY ,

GIVE YOUR LOAD COBMN  BASED ON YOU DESIGN CODE ,

IF YOU STILL FACING PROBLM
THEN ATTACH YOUR STAAD  FILE I WL SOLVE IT
BY
TBSPL_6


rahul_sharma1987 wrote:
Hello friends i am designing a pre engineered building on staaad pro.I am facing lots of problem like the rafters are failing in combined axial compression and bending(section7.1.1 IS 800 1983). I try to optimized it but it doent work the unity ratio is not
going below 1.7 and the size of rafter increased too much. Can anyone tell me some trick or some easy way to otimize my structure so that the structure doesnt fail and light weight also.
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rahul_sharma1987
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Joined: 09 May 2012
Posts: 8

PostPosted: Fri May 18, 2012 2:31 am    Post subject: problem in optimization on staad pro Reply with quote

I am attaching the staad file please check out this


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abc.rar
 Description:
staad file

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 Filename:  abc.rar
 Filesize:  3.5 KB
 Downloaded:  709 Time(s)

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er.mvv
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Joined: 03 Aug 2011
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Location: Hyderabad

PostPosted: Fri May 18, 2012 7:09 am    Post subject: Reply with quote

Dear Er Rahul

               So many discrepancies are found in the file. First of all, you please correct the loads and their application. Unless the model, boundary, conditions, loads and effective length factors are correct you cannot optimize. If you need help please send me the basic wind speed, internal pressure coeff... etc to m...



best regards

     MVV
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rahul_sharma1987
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Joined: 09 May 2012
Posts: 8

PostPosted: Fri May 18, 2012 8:02 am    Post subject: wind load calculations parameters Reply with quote

    
Basic Wind Velocity Vb = 47 m/s
Building category = C
Terrain Category = 4
k1 = 0.9
k2 = 0.67
k3 = 1
Design wind velocity = k1*k2*k3*Vb = 28.341
Design Wind Pressure = 481.93 0.48 m/s
Let us assume 5% opening in the building.
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venkatesh
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Joined: 29 Dec 2008
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PostPosted: Fri May 18, 2012 1:22 pm    Post subject: Reply with quote

Dear Rahul
Providing sag rods to purlins may help you lower down the Utilization ratio and these purlins shuld be released at ends.

Thanks & regards
Venkateshwar Rao
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TBSPL_6
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Joined: 17 Jan 2009
Posts: 28

PostPosted: Fri May 18, 2012 6:36 pm    Post subject: Re: problem in optimization on staad pro Reply with quote

DEAR RAHUL

I HAVE GONE THROUGH , YOUR STAAD FILE  , HERE YOU HAVE TO CONSIDERE A FEW FOLLOWING POINT

1. IS IT REALLY NECESSARY TO DO IT AS SPACE FRAME , PLZ TRY WE CAN DOI IT AS 2D FRAME  AS  IT IS A RIGID FRAME WITH LTO BLDG, OR IN THE INDUSTRY LANGUAGE  IT IS AN UNSYMMETRICAL CB1 BLDG

2. WIND LOAD YOU HAVE APPLIED ON THE MAIN RAFTER VERTIVALLY DOWN WARDS , IT NOT CORRECT , THERE IS BOTH PRESSURE AND SUCTION .

3. WHAT IS THE INTERNAL PRESSURE COEFFICIENT.

4. PLZ CHECK THE DESIGN COMMANDS  LY IS NOT CORRECT . LZ ALSO NEED MODIFICATIONS

5. PLZ MENTION THE UNL FOR THE  RAFTERS AND COLUMNS .

6. WHAT IS THE BLOCK WALL CONDITION  IN THE PERIPHERY OF BLDG .

7.FOR THE WIND LOAD APPLICATION CODEIS 875-PART3 ,  THER EXTERNAL PR.COFFICIENTS VARY FOR THE MAIN BLDG AND LTO BLDG, THESE YOU HAVE TO APPLY .

8. BASED ON THE TYPE OF SHEETING  WE CAN GIVE PURLINS SPACING.

NOTE: WHENEVER YOU ARE POSTING A FILE FOR GENERAL DISCUSSION YOU HAVE TO GIVE  COMPLETE DATA OF BLDG( U CAN WRITE IN THE STAAD  INPUT FILE FOR THE ASSUMED  VALUES AND CALCULATIONS ALSO ) , WHAT IS EXISTING , WHAT IS PROPOSED , WHAT IS THE REQMT, FUTURE PROVISIONS . ETC TO DO BETTER OPTIMIZATION.

BYE
TBSPL_6



rahul_sharma1987 wrote:
I am attaching the staad file please check out this
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