No problem Juan! It's buried in the whole q = V * Q / I equation. Q is the area outboard of the section you're cutting through times the distance from the centroid of that area to the centroid of the overall shape, and it's the only part that changes as we march along the shape. The overall shear V and the overall shape I-value are constant everywhere. When you're in the horizontal flanges, the distance centroid-to-centroid remains constant, it's just half the height of the overall shape minus half the thickness of the flange, so the only part that's increasing is the area, which goes up linearly as we move along the flange. In the vertical web, two things are going into that increasing Q. We've got the area increasing at a linear rate again as we slide down the web, but also have the centroid-to-centroid distance shifting, which multiplies by our coordinate again, giving that second order, or parabolic, distribution. Does that clarify it? Happy to explain further or shoot a video expanding on that if it's at all unclear!
@@StructEdOrg thank you so much for replying. I understand it more now, but I think I’m still struggling to visualize it a little bit. I will try to go through it again to see if I can make more sense of it. Thanks again!
Thank you for the video. So what do I do to avoid torsion for PFC while shear centre is locating outside the section ? How to deal with torsion when the load is actually applied on the top flange ?
Thanks Fedor! So unless you load at the shear center, the torsion is going to always be there, and your best defense is to somehow incorporate tubular shapes into your structural member. Otherwise, anything you can do to either try to get the load applied closer to the shear center, or to move the shear center closer to the load will help to limit the eccentricity and therefore your torsion on your section. Even a tiny little tube applied somewhere on your shape helps tremendously! If you have a specific design question, definitely feel free to email and we can discuss more! eric@structed.org
@@StructEdOrg wow. This is so detailed explanation. At uni, they taught how to get shearcentre but they didnt teach what to do after getting the shear centre (maybe they dis but I am the one who forgot) Thank you
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I’m struggling to understand why the shear distribution is parabolic at the vertical section of the c section and linear at the horizontal ones.
No problem Juan! It's buried in the whole q = V * Q / I equation. Q is the area outboard of the section you're cutting through times the distance from the centroid of that area to the centroid of the overall shape, and it's the only part that changes as we march along the shape. The overall shear V and the overall shape I-value are constant everywhere.
When you're in the horizontal flanges, the distance centroid-to-centroid remains constant, it's just half the height of the overall shape minus half the thickness of the flange, so the only part that's increasing is the area, which goes up linearly as we move along the flange.
In the vertical web, two things are going into that increasing Q. We've got the area increasing at a linear rate again as we slide down the web, but also have the centroid-to-centroid distance shifting, which multiplies by our coordinate again, giving that second order, or parabolic, distribution.
Does that clarify it? Happy to explain further or shoot a video expanding on that if it's at all unclear!
@@StructEdOrg thank you so much for replying. I understand it more now, but I think I’m still struggling to visualize it a little bit. I will try to go through it again to see if I can make more sense of it. Thanks again!
@@StructEdOrg thanks a lot!
Thank you for the video. So what do I do to avoid torsion for PFC while shear centre is locating outside the section ? How to deal with torsion when the load is actually applied on the top flange ?
Thanks Fedor! So unless you load at the shear center, the torsion is going to always be there, and your best defense is to somehow incorporate tubular shapes into your structural member. Otherwise, anything you can do to either try to get the load applied closer to the shear center, or to move the shear center closer to the load will help to limit the eccentricity and therefore your torsion on your section. Even a tiny little tube applied somewhere on your shape helps tremendously! If you have a specific design question, definitely feel free to email and we can discuss more! eric@structed.org
@@StructEdOrg wow. This is so detailed explanation. At uni, they taught how to get shearcentre but they didnt teach what to do after getting the shear centre (maybe they dis but I am the one who forgot) Thank you
great but tau is shear stress not shear force, shear force is V . Thank you this was very good
Thanks Ed
Any time! And happy to make any videos on topics you could benefit from!
0:41 awful in 'twisting' you mean?
You got it! I seem to have misspoken 🙈