The idea of beam acting as supports to slabs doesn’t really sit well with me. In terms of supports, I believe columns are the only true support in any structure. The beams and slabs work in tandem in a floor system by sharing and transferring moments and shear according to their relative stiffness ratios. Great tutorial sir Thank you for the doubt clearing session.
I agree with you for most normal structures, as the slab and beam (especially if hidden beams) are cast monolithically. (hidden beams are beams that have the same thickness as the slab, this is standard practice in slabs called: ribbed slabs in the Middle-east region). In bridges, I am a little more skeptical to be honest. Thnx for your comment, stay tuned for more content. Regards, CEE
The beam is normally cast with an offset to the slab's center. This greatly increases its moment of inertia about the slab's center axis, and stiffens the entire system. If you model this in Robot, you will get more realistic results. However, you will get some additional axial force in the beam, due to this offset, that is not easily negligible.
Hi there, a huge thnx for your comment. you are right. Offsets should be included, but the way RSA models those is really strange. It just connects some rigid links, causing jagged moment diagrams. Thus, I think the effect of such an offset should be pre-calculated manually (for example axial and moment effects) and then applied on the bridge. Note that, if you have an offsetted beam, and you discretize it (because there is a slab for example), then each node will be connected via a rigid link. So, I agree with you, but may suggest that the effect of offsets be calculated manually and applied as forces. Of course, that is my own humble opinion. Feel free to suggest alternatives, I always welcome all ideas. Regards, CEE
@@CivilEngineeringEssentials My approach to the problem involves manual calculation of the stiffness of the offset beam with respect to the axis of the slab and then entering a stiffness correction coefficient for the main moment of inertia of the beam, thus increasing its stiffness. In other words - offset is accounted for in terms of stiffness, but not applied geometrically to the model. In my opinion, results are more credible.
Hello CEE; Yep, the notion is now gone bye-bye 😊; thanks to the CEE remarkable understanding of various engineering concepts, the CEE patience and exemplary demonstrations herein provided in this regard. I really admire the way that the CEE have dissected this topic and I am inspired to explore similar approach when I investigate or research other subjects or topics of my own [In the words of the CEE, “….I have just learned how to learn….”. Well done and thank you so much for this video. Kind regards, DK
Hi there Engr. DK, You are most welcome. I am happy it helped. I think such issues are important to be discussed, especially to stop the "black box mentality" that seems to be widespread nowadays. A mentality that states: well the software says so. Regards, CEE
I would argue that there is no longitudinal moment in the slab as the slab was poured as wet concrete so no stiffness. When the shuttering and supports were taken away, then there would be only transverse effects mostly. But indeed, the stiffness in 3D is something one shall be careful with. Cheers. Good tutorials, I do like them. Thanks
I agree with you. Especially if the slab is cast and reinforced separately. However, as you have correctly mentioned, structural software's are notorious in just connecting everything. One should be careful with his model. I am happy you like those tutorials. Stay tuned for more content. Regards, CEE
@@CivilEngineeringEssentials you are welcome. Construction phases or stages are notoriously missed; I am not saying ignored, as ignored would mean that one had an awareness about it. An extensive tutorial about phases would be really welcomed. Thank you .
The idea of beam acting as supports to slabs doesn’t really sit well with me. In terms of supports, I believe columns are the only true support in any structure. The beams and slabs work in tandem in a floor system by sharing and transferring moments and shear according to their relative stiffness ratios.
Great tutorial sir
Thank you for the doubt clearing session.
I agree with you for most normal structures, as the slab and beam (especially if hidden beams) are cast monolithically.
(hidden beams are beams that have the same thickness as the slab, this is standard practice in slabs called: ribbed slabs in the Middle-east region).
In bridges, I am a little more skeptical to be honest.
Thnx for your comment, stay tuned for more content.
Regards,
CEE
Thank you for your videos!
Most welcome. Stay tuned for more content.
Thanks for sharing sir
Most welcome. I wish you all the best,
CEE
The beam is normally cast with an offset to the slab's center. This greatly increases its moment of inertia about the slab's center axis, and stiffens the entire system. If you model this in Robot, you will get more realistic results. However, you will get some additional axial force in the beam, due to this offset, that is not easily negligible.
Hi there, a huge thnx for your comment.
you are right. Offsets should be included, but the way RSA models those is really strange. It just connects some rigid links, causing jagged moment diagrams. Thus, I think the effect of such an offset should be pre-calculated manually (for example axial and moment effects) and then applied on the bridge.
Note that, if you have an offsetted beam, and you discretize it (because there is a slab for example), then each node will be connected via a rigid link.
So, I agree with you, but may suggest that the effect of offsets be calculated manually and applied as forces.
Of course, that is my own humble opinion. Feel free to suggest alternatives, I always welcome all ideas.
Regards,
CEE
@@CivilEngineeringEssentials My approach to the problem involves manual calculation of the stiffness of the offset beam with respect to the axis of the slab and then entering a stiffness correction coefficient for the main moment of inertia of the beam, thus increasing its stiffness. In other words - offset is accounted for in terms of stiffness, but not applied geometrically to the model. In my opinion, results are more credible.
Hello CEE;
Yep, the notion is now gone bye-bye 😊; thanks to the CEE remarkable understanding of various engineering concepts, the CEE patience and exemplary demonstrations herein provided in this regard.
I really admire the way that the CEE have dissected this topic and I am inspired to explore similar approach when I investigate or research other subjects or topics of my own [In the words of the CEE, “….I have just learned how to learn….”.
Well done and thank you so much for this video.
Kind regards, DK
Hi there Engr. DK,
You are most welcome. I am happy it helped. I think such issues are important to be discussed, especially to stop the "black box mentality" that seems to be widespread nowadays. A mentality that states: well the software says so.
Regards,
CEE
I would argue that there is no longitudinal moment in the slab as the slab was poured as wet concrete so no stiffness. When the shuttering and supports were taken away, then there would be only transverse effects mostly. But indeed, the stiffness in 3D is something one shall be careful with. Cheers. Good tutorials, I do like them. Thanks
I agree with you. Especially if the slab is cast and reinforced separately. However, as you have correctly mentioned, structural software's are notorious in just connecting everything. One should be careful with his model.
I am happy you like those tutorials. Stay tuned for more content.
Regards,
CEE
@@CivilEngineeringEssentials you are welcome. Construction phases or stages are notoriously missed; I am not saying ignored, as ignored would mean that one had an awareness about it. An extensive tutorial about phases would be really welcomed. Thank you .
@@TomKrok That is an amazing idea. I think it warrants having a lecture "theory" about it.
K = E I / L 😊
Yep, just worth mentioning that it is sometimes with an L^2 and sometimes with other factors (see the FEM series in beams ^_^)