Lion06
Structural
- Nov 17, 2006
- 4,238
I hope I don't come across foolish here, but I'm having a hard time understanding something. Let me explain the sketch I've posted before people start tearing it apart. This is not an actual detail, it is merely to help get across the point of my question.
The question is if you have a detail similar to this (whether it is a beam to column, or a column to ftg), would you use d for the moment arm to design the tension in the top anchor or (approximately) d+2g ( I know it would be from the top anchor to the centroid of bearing at the bottom angle, but just for argument's sake say d+2g)?
Does your answer change if you provide stiffeners such that the angles can be considered very stiff?
I'll give my opinion and explanation, then you can tear that apart.
I think you should use d as the moment arm in either case. I am differentiating this from a baseplate because a baseplate is a single (considered rigid) element that has a moment applied to it. This detail (whether stiffeners are present or not) has two individual angles with a tension and compression force applied seperately at a given location. While the baseplate is seeing 0 net force, moment only (assuming moment only and no axial load), these angles are each seeing a tension (or compression) force via the weld (not a moment only with 0 net force like a baseplate). I believe this applied whether the angles can be considered infinitely stiff or not because of the above reasons and the fact that they are so close to the end. If the angles were WT's and extended for some distance into the span of the beam such that the WT's had the opportunity to become fully engaged in helping to resist the moment, I would feel differently, but the angles (as they are currently shown) do not have that ability.
Any opinions?
The question is if you have a detail similar to this (whether it is a beam to column, or a column to ftg), would you use d for the moment arm to design the tension in the top anchor or (approximately) d+2g ( I know it would be from the top anchor to the centroid of bearing at the bottom angle, but just for argument's sake say d+2g)?
Does your answer change if you provide stiffeners such that the angles can be considered very stiff?
I'll give my opinion and explanation, then you can tear that apart.
I think you should use d as the moment arm in either case. I am differentiating this from a baseplate because a baseplate is a single (considered rigid) element that has a moment applied to it. This detail (whether stiffeners are present or not) has two individual angles with a tension and compression force applied seperately at a given location. While the baseplate is seeing 0 net force, moment only (assuming moment only and no axial load), these angles are each seeing a tension (or compression) force via the weld (not a moment only with 0 net force like a baseplate). I believe this applied whether the angles can be considered infinitely stiff or not because of the above reasons and the fact that they are so close to the end. If the angles were WT's and extended for some distance into the span of the beam such that the WT's had the opportunity to become fully engaged in helping to resist the moment, I would feel differently, but the angles (as they are currently shown) do not have that ability.
Any opinions?
