Beam Strengthening with Web Plates
Beam Strengthening with Web Plates
(OP)
I have an issue on a job I'm working on where it is proposed to increase the loads on the structure. I have assessed the capacity of the existing beams (recent steelwork, Grade S275) and one of the beams is failing by approx. 8%. The architect is not amenable to the use of flange plates to strengthen the beam as head height is already tight. Therefore, I am proposing web plates, site welded to each side of the web. This would increase the section modulus and to ensure that the beam has sufficient capacity. The steel fabricator has queried this as he is concerned that the effect of heat from welding may weaken the beam. He has suggested bolting web plates instead.
1. Is there a risk of site welding weakening the beam?
2. Will a bolted web plate solution in fact increase the section modulus?
3. Would the bolts have to be HSFG?
4. How would I design the bolts?
Thanks
1. Is there a risk of site welding weakening the beam?
2. Will a bolted web plate solution in fact increase the section modulus?
3. Would the bolts have to be HSFG?
4. How would I design the bolts?
Thanks






RE: Beam Strengthening with Web Plates
RE: Beam Strengthening with Web Plates
RE: Beam Strengthening with Web Plates
Mike McCann
MMC Engineering
http://mmcengineering.tripod.com
RE: Beam Strengthening with Web Plates
If you are concerned about the welding weakening the beam, provide a prop at midspan, just a wood post or a telepost.
BA
RE: Beam Strengthening with Web Plates
If not, not a big deal, but would be interesting to see as well.
Cheers.
RE: Beam Strengthening with Web Plates
BA
RE: Beam Strengthening with Web Plates
The problem with both welding and bolts is the increased likelihood of fatigue damage. If you welded plates on then the welds may be near the flanges and so see higher stresses. With bolts the concern may be with the stress concentration from the bolt hole, but if these are near the neutral axis of the beam, less of a concern.
For the bolted connection you have to consider the horizontal shear forces in the beam set against the shear capacity of the joint. Have a look at this site ht
RE: Beam Strengthening with Web Plates
As a side note: If the area is accessible from above, and only flexure and deflection is a concern, then increasing the capacity as a composite beam by field welding shear studs to the top flange could also be considered. This also requires saw cutting of the existing slab and field repairs.
RE: Beam Strengthening with Web Plates
I am not MikeTheEngineer, but thank you for the complement.
That being said, if you do intend to take this approach to strengthen the beam, remember to deload the beam with shoring prior to any strengthening, or the beam will have initial embedded stresses that will not be relieved by the strengthening process.
Mike McCann
MMC Engineering
http://mmcengineering.tripod.com
RE: Beam Strengthening with Web Plates
I fully agree with you about relieving the member of the load prior to strengthening measures.
RE: Beam Strengthening with Web Plates
RE: Beam Strengthening with Web Plates
go to:
www.steeltools.org
and search "BEREIN13"
Tomanovich has made a spreadsheet for just about every way you can imagine reinforcing a wide flange.