Design of V shaped RCC columns
Design of V shaped RCC columns
(OP)
I am invoved in the design of an octogonal shaped RCC building.
Is there a design procedure or a handbook to design V shaped RCC columns (with an included angle of 135 deg.)?
Thanks for the help
Trilinga
Is there a design procedure or a handbook to design V shaped RCC columns (with an included angle of 135 deg.)?
Thanks for the help
Trilinga






RE: Design of V shaped RCC columns
RE: Design of V shaped RCC columns
Do you mean V shaped in section or in plan.
Can you post a sketch?
RE: Design of V shaped RCC columns
Trilinga
RE: Design of V shaped RCC columns
RE: Design of V shaped RCC columns
Apart from FEM, this doesn't end our possibility of action: we can determine also the standing elastic stresses by the usual formulas, then dimension, say, yes, even for shear friction of the worst. Anyway for critical columns like yours likely important you will get better appraisal with the better 3D FEM model that you can afford, since by the approximations and without a reference struts crushing and other things like that that may be critical could go overlooked.
RE: Design of V shaped RCC columns
BA
RE: Design of V shaped RCC columns
We simply used PCACOL (the irregular column package that you get with the software).
So I guess I cheated and used a program.
RE: Design of V shaped RCC columns
I must apologise for not making my query precise.
The building is a three storeyed structure octagonal in shape.
The columns at the corners of the octagon receive beams from either side of the corner of the octagon.
The columns are 12" wide 24" along the perpendicular direction.
The shape of the column is shown in the enclosed sketch.
I could not locate any design charts or design procedure to design this non-rectangular reinforced concrete section subjected to axial load and biaxial bending.
I need help in getting the design method.
RE: Design of V shaped RCC columns
Link to PCA spColumn program
RE: Design of V shaped RCC columns
I include pdf and the worksheet itself in the attachment. It may work or not (and then need minor adaptations) in later versions of mathcad.
The problem with this is that you at most can deal with this with longitudinal stresses, but interaction with other torsion and shear forces, buckling itself need be dealt complementarily. So I stand with trying to investigate the member as solid in FEM to ensure you are safely enough free of any limit strength problem.
RE: Design of V shaped RCC columns
JAE, Prior to starting this thread, I have almost concluded to your suggestion of doing the design by hand from first principles. You have reconfirmed it.
I do not have the PCA software but I can try to get it.
Ishvaag, I will also try to understand the method given in your Mathcad attachment.
Thank you both once again
Trilinga
RE: Design of V shaped RCC columns
If you look at a good RC text book (or your engineering course notes) it will give a method of calculating section capacities for concrete sections of any shape fopr any combination of M and N applied.
This is the basis of RC design. You should not have to rely on design charts. I agree they are usefull but you should understand the theory of how they are generated so that you can generate your own for column shapes not covered by charts.
Do it manually, it will be a good learning experience for you.
RE: Design of V shaped RCC columns
RE: Design of V shaped RCC columns
1. Plane sections remain plane after bending (i.e. strain profile is linear).
2. Assume some sort of stress-strain profile for concrete (linear would be easiest).
3. Concrete strain doesn't exceed 0.003 or 0.0035.
I would even be inclined to calculate the pure bending moment (i.e. if designed as a beam), balanced load and squash load and draw a line between the three points and keep within this line.
Because the section is only singly symmetric you should calculate the capacities when the shape is V-up and V-down because the different distributions of reinforcing steel will result in different capacities.
For biaxial bending, I would use code simplifications. I would not even attempt to rotate the cross-section to calculate capacities.
Best of luck.
P.S. FOR PEOPLE THAT HAVE PREFORMED THE CALCULATIONS BY HAND, WHAT STRESS-STRAIN RELATIONSHIP DO YOU USE FOR CONCRETE?
RE: Design of V shaped RCC columns
I can't see any reason not to use a rectangular stress block using the applicable code provisions for the Ultimate Limit State, and linear elastic for serviceability.
Also I agree with checking bending capacity about both axes and using whatever method is in the code for biaxial bending to combine them.
Doug Jenkins
Interactive Design Services
http://newtonexcelbach.wordpress.com/
RE: Design of V shaped RCC columns
RE: Design of V shaped RCC columns