Which stress to use in a steel-plate

[As-Lag]

Hello

I am sizing a flitch-beam and I want to know what yield stress to use for the steel. The steel-supplier quotes two figures for a 300x15 mm steel plate. The steel is S275JR and the minimum Yield is 275 N/sq.mm and a strength limit of 410-560 N/sq.mm.

Should I use 275 N/sq.mm or may I use the 410 N/sq.mm?

Regards

 

[rb1957]

yield would be the lower number.

another day in paradise, or is paradise one day closer ?

 

[As-Lag]

Thanks. Thought so.

 

[HTURKAK]

Typical allowable stress σ all = 0.6 Fy and for S 275 σ all = 275*0.6=165 Mpa.

 

[Agent666]

There have been quite a lot of posts regarding flitch beams here in the past. A search would enlighten you.

One thing regarding going straight to the maximum allowable steel stress is that you need to be mindful for flitch beams that the timber may in fact be the limiting factor. If timber fails first then your steel stress at this failure point will probably be lower than the elastic capacity. Most commercial flitch beams are proportioned so this does not occur (at least based on my local experiences), but if you're making your own flitch beam up it is something that should be checked as it can occur. Review this on the basis of strain compatibility to determine which material reaches its limiting strain first, and pro-rata the strengths accordingly for the other materials based on the limiting strain.