bjb
Structural
- Nov 8, 2002
- 455
I recently have been contemplating reinforcing some steel beams using an LRFD approach. I typically in the past have used an ASD approach, but I have a paper that goes into an LRFD approach that is very interesting to me.
I am looking for a reality check for the case when you have an existing A36 steel roof beam under light dead load only.
It is desired to field weld a new wide flange to the bottom, but wide flange material today is typically Fy=50 ksi. I calculate the location of the PNA, plastic section modulus, and the factored moment strength on 36 ksi for the existing and new sections-is that reasonable?. The plastic neutral axis is very close to joint between the 2 beams. It seems like a reasonable approach to me. When the existing section goes plastic, from equilibrium the force in the new and existing sections has to be equal. Also, the distance between the resultants in the new and existing sections is greater than if both sections were plastic, since in the new section there would be a triangular stress distribution.
I am looking for a reality check for the case when you have an existing A36 steel roof beam under light dead load only.
It is desired to field weld a new wide flange to the bottom, but wide flange material today is typically Fy=50 ksi. I calculate the location of the PNA, plastic section modulus, and the factored moment strength on 36 ksi for the existing and new sections-is that reasonable?. The plastic neutral axis is very close to joint between the 2 beams. It seems like a reasonable approach to me. When the existing section goes plastic, from equilibrium the force in the new and existing sections has to be equal. Also, the distance between the resultants in the new and existing sections is greater than if both sections were plastic, since in the new section there would be a triangular stress distribution.
