how to specify weld size for rebar to plate 1

[ajk1]

When welding rebar to plate to develop the rebar, do I need to specify a weld size, or is what I have shown on the attached sufficient?

 

[spieng89]

You would need to specify the weld size and type of weld e.g. groove weld 1/4" thick, 3.5" long

 

[ajk1]

Where is the 1/4" measured from?

Is it from the centre of the bar outward 1/4"each side?

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If so, how do I evaluate the effective thickness? Is 1/4" groove weld the same capacity as 1/4" fillet weld?

 

[SAIL3]

it is a partial penetration flare bevel weld...effective weld is usually about 5/8th of the depth of the weld...I would also tend to back it up with a fillet weld...

 

[JAE]

You would specify an effective weld with parentheses around the required throat.

Agree with SAIL3 on the 5/8 concept. If you look at Table 8-2 in the AISC manual under Prequalified Flare-Bevel Groove welds for plate to tubes it provides some guidance - read the footnotes too.

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[transmissiontowers]

I'm no welding expert but from what I recall A615 should not be welded because it has too much carbon. I believe A706 is a weldable grade of rebar. Maybe someone can set me straight if I am incorrect.

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[ajk1]

I have specified weldable grade rebar (Canadian grade metric 400W, which we have used before and is readily available) so that is definitely not a problem.

What I still do not know, perhaps because I do not have the AISC handbook, is how to specify the weld, and what it means.

To develop the 20M rebar (300 sq.mm or 0.465 sq. inches) I need to develop a factored force of 120 kN or 27000 pounds factored force.

A 1/4" fillet weld can develop 0.826 kN/mm of length, so 76 mm length can develop 2 sides x 76 mm length x 0.826 = 126 kN

How do I specify that for a partial penetration flare bevel weld?

Where is the weld depth measured from? If the bar is 20 mm diameter, is the depth of the weld equal to 1/2 x 20 = 10 mm?

If so, then 5/8 x 10 = 5 mm. Please let me know if that is right.

What does the digit 6 mean in your sketch?

What do you mean by backing it up with a fillet weld? Where does it go? And what size fillet?

Thanks.

 

[MacGruber22]

effective weld is usually about 5/8th of the depth of the weld...I would also tend to back it up with a fillet weld...

You cannot just add the strength of a fillet weld to the flare-bevel groove weld. As an example: Link

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[ajk1]

MacGruber22 - ok, this is what I think I am looking for. I will study it. Thanks.

 

[wannabeSE]

In JAE's sketch, the number in parenthesis is the effective throat (weld size). The 6 denotes a 6" long weld.

When the effective throat is not shown on the flare bevel groove weld symbol (like ajk1's attachment), the weld is assumed to be filled flush. For reinforcing (AWS D1.4), the effective throat when filled flush is 0.4 times the bar radius. For structural steel (AWS D1.1), the effective throat when filled flush depends on weld process. For SMAW, FCAW-S and SAW the effective throat is 5/16 times the radius. For GMAW and FCAW-G, the effective throat is 5/8 times the radius. To determine the effective throat of a weld that is not filled flush, the unfilled depth is deducted from the filled flush size. For rectangular HSS, the radius is assumed to be 2 times the wall thickness.

 

[SAIL3]

MacGruber is corect about the added fillet weld not being counted as far as strength....I use it because it is difficut for a welder to end up with a flush weld..either it ends up being undercut(undesireable) or is overfilled...adding the additional fillet weld is an extra measure to prevent the undercut ...at least, that is my line of thinking....

 

[ajk1]

To wannabeSE - you have provided a clear, concise and complete explanation to all the questions that I posed. I very much appreciate that. It is very helpful. I will print it out and add to me design guides. Thank you.

To SAIL3 - thanks for the help. Much appreciated.