Thank you Retrograde for replying.
Yeah I did it that way. His equations don't address the case where the column length is more than twice the width ( like slender concrete walls ). In that case I can get significant increase in Ise, as the software results agree.
It's just that the...
Concrete column buckling load (Pc) decreases significantly as the rigidity (EI) increases. The rigidity (EI) increases as the section stiffness (Ig) increases and as the reinforcement moment of inertia about the centroidal cross section (Ise) increases.
My question is, how to calculate the...
Thank you Kootk for replying.
Both great approaches. With the first one I can reduce uplift by (40-50) percent without having to assume gravity is not present [bigsmile]. I just need to pay attention that the smaller section is not over reinforced.
Also, I think applying the first approach...
Thank you everyone for replying.
I think it's not a good detail, but withstanding the explicit code requirements, I have seen some plans where the beams were assumed and designed to act as simple beams. This is done by designing each span as simply supported and provide one third the bottom...
In reinforced concrete continuous beams with unequal spans similar to the attached sketch. Under gravity loading Column (A) has an uplift reaction. How would you detail the beam to column joint to transfer this uplift force ?
Also since this uplift force causes an increase in the reaction at...
Thank you Kootk and TLHS for replying. I am currently not working on a similar situation, I was just wondering about the concept. I plan on taking the time to study this situation with different loading cases on each column and experiment with it.
Thank you Tom for replying, I would not consider the height halved, but I do agree with JAE that it will help if one column was loaded more than the other. Still, it won't be enough to decrease the heavily loaded column dimension significantly maybe by ( 5 to 10 percent ). I think it's better to...
Thank you 3DDave and JAE for replying. So this configuration is helpful to increase the capacity of the heavily loaded column but at the expense of the lighter ones. In concrete we calculate the buckling load for a column based on it's height, reinforcement and section to determine the...
Thank you BAretired for replying,
Yeah the four columns are all connected with concrete beams, I agree that it's not a good detail.
Still, it is interesting to know to what extent they will help each other.
In situations similar to the attached sketch, where one of the stories is higher than the other stories. Looking at the elevator columns. As a concept, I am wondering whether adding concrete beams connecting all of the columns in the middle of the floor height, would be sufficient in reducing...
Interesting, it's weird that the local building code doesn't require a minimum. I never thought contractors would try to save money on a couple of anchor bolts.
I live in a different continent but I can't help but wonder even if uplift is not an issue. If bolts are not required, then how does the lateral force resisting steel frame transfer the shear force into the footing ? Is it relying on a concrete shear wall ?
Thank you Ron for replying. Yeah I agree with you, for a flagged sign, I would probably use a pile cap. Even for the case I sketched ( it was designed by another engineer ) I am not really convinced with the single footing solution. Having to provide minimum reinforcement for such a large...
I am interested in billboard signs design and I got my hands on the structural plans of one. The Billboard sign dimensions are 12 meters x 4 meters with a total height of 40 meter form the top of the footing to the billboard sign center. I added a sketch for reference. The footing dimension are...
Again thank you Kootk and BAretired.
I understand now thank you.
When the time comes to design one of these buildings, maybe it would be best to use braced frames with shear walls and tell the Architect to deal with it. [bigsmile]
Thank you KootK and BAretired for replying.
What if they are a part of sway frames ( cantilever column action )? K will be large and the columns design height should be the entire building height not just one story.
If the beams were cast on site as we do in typical concrete structures, but...
In Multi-story precast concrete buildings, where the columns are cast on site, while the beams and the slabs are precast. The beams simply rest on the corbels, so the columns are not restrained by the beams or the slab, therefore what K factor should be used ?
Also. What height should we...
