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Why would a piece of round stock be welded to the inside corner of ... 1

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jpyeron

jpyeron

Electrical
Jan 17, 2010
24
Why would a piece of round stock be welded to the inside corner of angle Iron?

I have been observing a truss framed roof from 1921. The angle irons on the upper parts of the trusses have a round stock of a diameter approximately 1/3 the flange width.

What could the reason be for the round stock?

 
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For angle-iron trusses, i.e. Bar Joists, stitch welding a 'round bar' to an angle is the usual-and-customary method of reinforcing the truss. Typically only used on the bottom - tension - side of a truss.

Look for torch nicks -- this bar may have been put there to remediate a flaw in the top chord.
 
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Or they one time added load to the truss/joist and needed to strengthen the truss for the higher load.

 
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Perhaps they weren't able to get angles of the size indicated by calculation, used a built-up version as a substitute.

There wasn't much welding being done in 1921, and if the rest of the structure is riveted, I would suspect it was added after the fact.
 
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To either increase the compression strength of the top chord or increase the minimum lateral buckling length of the top chord.

Mike McCann
MMC Engineering

 
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How does adding the round stock on the inside corner add (significant) strength?

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How good is the weld?
Is the round stock and angle still corrosion free and "safe", or deteriorated and falling apart?
What sizes of each?
How much weld is in place?
 
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3" weld every 9" alternating top and side flange.
angle iron, round stock and welds appear to be in good condition.

angle iron is 4"x6"x3/8"
round stock is about 1" dia
 
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jpyeron,
The bars add ultimate tensile strength in direct proportion to the area added, provided that the bar force is adequately developed at the ends, and also provided that the bar and angles have the same yield strength. If added to a compression member, the strength would also be increased, but probably not to the same extent as for a tension member because of the tendency of the member to buckle.
 
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Hokie:

In looking aat the picture, the bar is not continuous. It is not related to increasing the section.

There was a preveous mention of being a possible repair - could be a backing bar for that?

Mike McCann
MMC Engineering

 
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Mike...look again...it is continuous. Weld gives impression of discontinuous.

This was added later for reinforcement. Many reasons to reinforce....added load, change of classification, code mandate, etc.
 
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So the round would add strength along its length primarily but not against twisting and deflection?
 
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It would increase the section properties and would have some effect on buckling strength as well as deflection.

The difference in yield would have limited effect on the ultimate strength... barring second order effects, after the first section yielded, the higher Fy would continue taking load until it, too, yielded. A slight 'hiccup' in the load deflection diagram.

Dik
 
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It is possible for this to have been original work. Until just after WW2, material was more expensive than labor and sometimes the manager, a non-engineer would get a good price on the wrong material and order the designers to find a way to use it. Even in the early sixties at an American owned company, we changed bolt sizes to keep the inventory moving.

Michael.
Timing has a lot to do with the outcome of a rain dance.
 
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You're right Ron - I was seeing the intermittent welds as the bars. Thanks.

Mike McCann
MMC Engineering

 
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