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section modulus of weld

 
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anshuljn
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PostPosted: Fri Oct 02, 2009 7:31 pm    Post subject: section modulus of weld Reply with quote

There is a problem I am facing while designing a welded connection in eccentric loading. An I-section is needed to be welded to a plate via fillet welds(Figure attached) of size 8mm(throat thickness - 0.707*8 mm).

While calculating the bending stress in weld, section modulus of weld group is required to be calculated. What would be the section modulus of weld in this case (weld shown in figure attached) ? Also what is the methodology of calculating the same ?

Thanks in advance.



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gsparsan
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PostPosted: Sat Oct 03, 2009 12:59 pm    Post subject: Reply with quote

Steel Designers' Manual (published by SCI, UK) has a methodology of calculating eccentrically loaded weld groups for different shapes and load situations.

In your case, is it a cantilever beam? If so, I would personally use a short-cut as follows: Find the axial load in the top and bottom flange and design the weld around the flanges individually for that axial load. The weld around the web can be assumed then to take the shear only.

Alternatively, check if the weld is a full-strength one (sum of throat thickness >= plate thickness, i.e. 2 x 0.7 x 8 >= Flange thickness). Then there is no need to check the weld. The weld is at least as strong as the section and therefore if section is ok, weld is also ok.
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engineer2share
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PostPosted: Sat Oct 03, 2009 6:14 pm    Post subject: Section Modulus of weld Reply with quote

Axial force transfer by the entire area of the section. Hence find out area distribution of flange and web and calculate the corresponding axial force.

Convert the moment into couple force at top and bottom flange. (M/(D-T)). Add the proportionate axial in flange and the couple force.

You will get the total axial in flange. Design the flange weld for this total axial.

The web weld will be designed for the proportionate axial on web and shear on web. Take resultant of shear and proportionate axial and design the web weld.

A fillet weld can not be assumed as full strength weld whatever its size. If the size of fillet weld exceeds the thickness of the connecting member, provide Continuous Joint Penetration Butt weld (with 100% UT). But make sure your connecting element capacity is more than the applied load on the connecting element.

Dont forget to check the local effects on supporting member.

Have a nice day.
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revanwaghode
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PostPosted: Wed Oct 14, 2009 5:06 am    Post subject: section modulus of weld Reply with quote

Dear Anshul,
You can refer the book of "Design of welded Structures" By Blodgett.In this you will get the formulae to calculate the section modulus of line weld of few standard shapes.Or you can calculate manually as u calculate section modulus of any shape.Similar procedure to follow for line weld.
 
Regards
Abhay


On Sat, Oct 3, 2009 at 11:44 PM, engineer2share <forum@sefindia.org (forum@sefindia.org)> wrote:
Quote:
  Axial force transfer by the entire area of the section. Hence find out area distribution of flange and web and calculate the corresponding axial force.

Convert the moment into couple force at top and bottom flange. (M/(D-T)). Add the proportionate axial in flange and the couple force.

You will get the total axial in flange. Design the flange weld for this total axial.

The web weld will be designed for the proportionate axial on web and shear on web. Take resultant of shear and proportionate axial and design the web weld.

A fillet weld can not be assumed as full strength weld whatever its size. If the size of fillet weld exceeds the thickness of the connecting member, provide Continuous Joint Penetration Butt weld (with 100% UT). But make sure your connecting element capacity is more than the applied load on the connecting element.

Dont forget to check the local effects on supporting member.

Have a nice day.







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Dr. N. Subramanian
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PostPosted: Tue Nov 03, 2009 8:25 pm    Post subject: Re: section modulus of weld Reply with quote

Hi ER Anshul,

See Table 6.7 of my book Design of Steel Structures for properties of welds treated as lines. As suggested by other Sefians, you can also assume that the web welds carry the entire shear force and flange wels carry the entire BM. See Example 6.26 of the book.

Best wishes,
Subramanian
anshuljn wrote:
There is a problem I am facing while designing a welded connection in eccentric loading. An I-section is needed to be welded to a plate via fillet welds(Figure attached) of size 8mm(throat thickness - 0.707*8 mm).

While calculating the bending stress in weld, section modulus of weld group is required to be calculated. What would be the section modulus of weld in this case (weld shown in figure attached) ? Also what is the methodology of calculating the same ?

Thanks in advance.
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