propper welding of top and bottom plates to i beam

[velvetpants57]

I have a w27x114lb x 240"l I-beam with a 12"w x 240"l 1"t plate on top and a 12"w x 240"l x .625"t plate on bottom. The reason for the plates was to achieve the section modulus needed and to meet required existing heights and safety factor. What I am unsure of is appropriate welding practice to simulate these plates being part of the I-beam. We were originally going to bevel and seam weld all interface edges all around. I am worried about tempering the I-beam when introducing that much heat. So how much of a weld do I need. Can it be stitch welded 1 foot every foot or some other variant?
Thanks for the impute
Dallas


only in a steel mill.

 

[desertfox]

Hi velvetplants57

In a very old reference called "Design of structural steel work"
plates that are welded onto the top and bottom of a rolled beam can have space welding the spacing being a maximum 16 times the thickness of the thinner part in compression, in no case more than 300mm and 24 times the thickness of the thinner part in tension. Also the stiffening plates are not required to go beyond any point at which the applied bending moment falls below the bending strength of the rolled beam.
If the plates are automatic welded then the welds are usually continuous.

You really need the updated specs for this project but at least you know that the plates can be stitch welded.

desertfox

 

[chicopee]

What is the intended purpose of the build-up I beam?

 

[velvetpants57]

the beam will be for a 25 ton bridge crane used in scrap transer. the crane was originally built in 1927.the beam used originally is what can most accurately be described as an S 28 I-beam. from what i was able to find it is an old style of rolled beam which is no longer producted. horizontal beams are being replaced due to fatigue damage. ie years of patching without knowing what a stress point is.
desertfox, thanks for the reply just ordered the most recent version of that book.
thanks for the help
Dallas

 

[desertfox]

Hi velvetpants

your welcome.

 

[desertfox]

this might also be of use:-

http://www.modernsteel.com/steelinterchange_details.php?id=412

 

[velvetpants57]

that will be helpful for other projects. this craneway was built with all rivets. i plan on removing the hot rails, gas axing the rivints out of the joining/expansion plates and bolting this new beam in.

 

[Ron]

Determine the shear flow at the plate interface, q=VQ/I and size the welds accordingly.

For fatigue, consider using continuous welds rather than stitch welds.

 

[velvetpants57]

Ron,
would adding this much heat into the beam effectively temper the steel thus making it brittle and more prone to fatigue failure

 

[Ron]

No.

 

[desertfox]

Hi velvetpants57

As you're dealing with an overhead crane might it be advisable to talk to a crane manufacturer?
I am not sure that beams with strengthing plates are permissible for overhead crane construction.
Your strengthing plates top and bottom will increase the static strength of the beams but you increase the chance of fatigue failure of the doubler plate welds by only stitch welding them.
Have a look at this link:-

http://www.fgg.uni-lj.si/kmk/esdep/master/wg12/l0300.htm

it shows a doubler plate welded on a beam and gives classifications to the weld type and geometry in relation to possible fatigue failure.

I beams are completely fabricated by welding plates together so I don't see a problem welding doubler plates continiously.

desertfox

 

[boo1]

ASME B30.2-2005
2-1.4.2 Girders (for new)
.... conform to the design parameters as specified, in CMAA Specification No. 70 or AISE Technical Report No. 6.

2-1.4.3 Modifications
Cranes may be modified or rerated provided such modifications and the supporting structure are analyzed thoroughly and approved by a qualified person or manufacturer of cranes.

and look at posts

http://www.eng-tips.com/viewthread.cfm?qid=135452&page=4

 

[PEinc]

According to AISC Design Guide 15, building steel made between 1900 and 1939 was ASTM A9 steel. Therefore, your 1927 steel beam should be A9 steel. The Guide says that the weldability of A9 steel needs to be evaluated on a case by case basis. The Guide then describes a simple weldability test.

http://www.PeirceEngineering.com

 

[boo1]

If the welding for the cover plates are unbalanced, cambering will occur. For the cover plates we typically use fillet welds. Don't hook the cover plate weld around the corners.