huangyhg

across the flange welding
does anyone know of any references that address welding across the bottom flange of an existing beam?
this question keeps coming up and my only resourse is advice from my old supervisor that it should be avoided because heating up the tension flange could induce a permanent deflection. others have mentioned stress concentrations, but i have never bought that since the same would be true about the top flange.
any help out there?
i've received the same comments for a job (north of quebec). however there is maybe an acceptable way of doing it if you are able to place a stiffner in the existing beam right above the area you are about to weld. but i don't have any references to prove this (just an experience i had the welders do in our shop.
if you have any reference let us know.
welding across the tension flange is definitely not adviseable. if for no other reason, welders today are not that good and if your putting a fillet weld in there is usually and undercut issue giving rise to stress concentrations and loss of section issues.
what type of structure is the beam in??.....building?........bridge girder? (hopefully not!).........
aside from the practical issues of warping........welding across a bottom flange must be considered in terms of the reduction in allowable bending stress of the beam....welding affects the fatigue life .......generally you will have to reduce the allowable stress if there is any repetitive loadings to be considered.........for a bridge this would almost certainly not be considered acceptable.......
you should check the fatigue section of the aisc manual of steel construction......also the american welding society code for buildings and bridges......the details of the weld are important for any condition where stress is significant......minimum length of weld, end conditions........
i agree with jfman. its a definite no-no for beams subjected to repetitive loadings. will drastically reduce
allowable stresses.
cage

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