Dear STKO,
thanks for the answer.
Try this and see what happens when you refine the mesh.
I have made analyses for mesh sizes 0.7 and 0.4. For 0.7 the result of deflections I got as for elastic anlysis Uz=-0.02m, for size 0.4 I got UZ=-0.3.
Still the result depends on the mesh size, but the deflections are not of the order of 1.3m.
Then try to make the corner portions of the slab rigid (portions of the size of the column cross section) and see what happens
Please check if I understood correctly.
Method 1
In the existing plate, using lines, make a square with the size of the columns (for example, a 0.25x0.25 column). Then merge the lines with the slab. Give restraint on 4 edges (which are the edges of the columns) and they will change according to the size of the mesh.
Method 2
Make the corners of the plate as 4 small plates corresponding to the size of the column. Then merge them with the rest of the slab.
The main source of error is that you attached the column to 1 point of the slab (this indue huge shear forces to a single node of the slab).
In nonlinear analysis this will make the slab fail in out-of-plane shear. Because the shell section does not account for shear reinforcement.
This answer made me realize that I did not understand the principle of the elements I used. I would really like to ask you to answer some questions about shear, since in my work I mainly focus on bending and membrane action of the plate at large deformations. I am afraid that these very questions may occur during the presentation of my results.
1. You wrote that the slab failed due to shear (Vz) and that the multilayer shell element does not contain shear reinforcement. Then how much (or what) is the shear capacity of the slab? E.g. in designing according to the Eurocodes, the shear resistance of a slab without shear reinforcement is always checked first (just bending reinforcement is taken into account, so my 0 and 90 degree reinforcement).
2. I don't really understand the issue of shear in the slab. By anlizing the zone above the column, punching or bending failure can occur. Am I able to anlyze punching in the elements I use? If the supporting element would be a long wall, how am I able to check whether shear or bending failure has occurred?
This question introduces a 3rd way of modeling the Column Zone. How about making a 0.25x0.25 slab as an elastic slab? But won't this method result in not capturing the formation of a hinge due to bending, as happens in beams ?
3. Using ASD3Dconcrete material, shear failure is possible (it has a certain load capacity), but using a multilayer shell element, the shear capacity is zero?I don't understand this ralation. Is there somewhere a description of the layered shell element used in opensees from a mathematical point of view . The page that openssees in STKO does not have much information about it. (
http://www.luxinzheng.net/download/Open ... enSEES.htm)
4. Is the convention of internal forces in a shell element available somewhere? In the isntruction of STKO it is only that the forces refer to the local coordinate system. But what is, for example, the gamma of y13, y23, y12 in the section fiber strain result.
5. In summary, the main issue is whether yielding of the reinforcement due to bending or shear failure will occur first? Since the element has no shear resistance (as I understand it well, the multilayer shell element is responsible for this) and not asdshellq4 ? Unless only concrete is responsible for out-of-plane shear resistance ?
6. Just do I understand your procedure correctly. The procedure that you performed by adding Plateformplanestress caused that only bending damage can occur?
Best regards
