EngDM
Structural
- Aug 10, 2021
- 660
Hey all,
I've used a similar detail in the past for a typical connection to pick up a shelf angle to support a sidewalk or brick veneer, but usually there is no eccentricity horizontally since the supporting angle is continuous, or at least very little. I have a condition now where the eccentricity horizontally is roughly 4" in the horizontal, and 7" from face of column vertically. I'm trying to follow the load path to determine the angle size, and I've been trying to check the section identified in the sketch below for the torsional component. Not only will it have torsion, but also strong and weak axis bending (strong from gravity and weak from lateral loads due to occupancy/wind). I modeled a thin rectangular section in RISA 3D to see what approach they took, but the calculations for how exactly shear force due to torsion isn't shown, they just show a shear kN force and how they got there is lost on me. I have a copy of the theory of elastic stability but, as owners of this book know, it is DENSE and I have never really dug into it. I compared the value from the bt^3/3 equation for J to what RISA and other online calculators show, but they are different by a little bit. They appear to be using the beta parameter for b/t, but I'm not sure why this is used over bt^3/3.
I am also considering semi ignoring the contribution of the horizontal eccentricity since the supported element is concrete and it doesn't span that far, so any actual rotation of the slab at the support is minimal at best.
On another note, I am trying to figure out what the best way to size these welds is. There are some tables in CSA/AISC that deal with fully welded eccentric conditions, but not eccentric in 2 directions. Or I could use the WELDGRP spreadsheet, but I have noticed I get largely different requried weld sizes when doing the same condition by the AISC tables vs inputting into that spreadsheet, so I have taken a step back from using the spreadsheet until I can figure our why exactly this is. The spreadsheet gives WAY larger welds, so I'm not sure if it is because the tables don't use the elastic method, or what it is.
I've used a similar detail in the past for a typical connection to pick up a shelf angle to support a sidewalk or brick veneer, but usually there is no eccentricity horizontally since the supporting angle is continuous, or at least very little. I have a condition now where the eccentricity horizontally is roughly 4" in the horizontal, and 7" from face of column vertically. I'm trying to follow the load path to determine the angle size, and I've been trying to check the section identified in the sketch below for the torsional component. Not only will it have torsion, but also strong and weak axis bending (strong from gravity and weak from lateral loads due to occupancy/wind). I modeled a thin rectangular section in RISA 3D to see what approach they took, but the calculations for how exactly shear force due to torsion isn't shown, they just show a shear kN force and how they got there is lost on me. I have a copy of the theory of elastic stability but, as owners of this book know, it is DENSE and I have never really dug into it. I compared the value from the bt^3/3 equation for J to what RISA and other online calculators show, but they are different by a little bit. They appear to be using the beta parameter for b/t, but I'm not sure why this is used over bt^3/3.
I am also considering semi ignoring the contribution of the horizontal eccentricity since the supported element is concrete and it doesn't span that far, so any actual rotation of the slab at the support is minimal at best.
On another note, I am trying to figure out what the best way to size these welds is. There are some tables in CSA/AISC that deal with fully welded eccentric conditions, but not eccentric in 2 directions. Or I could use the WELDGRP spreadsheet, but I have noticed I get largely different requried weld sizes when doing the same condition by the AISC tables vs inputting into that spreadsheet, so I have taken a step back from using the spreadsheet until I can figure our why exactly this is. The spreadsheet gives WAY larger welds, so I'm not sure if it is because the tables don't use the elastic method, or what it is.
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