Impact of the corotaional using ASDSHELL Q4 and ASD CONCRETE 3D

[Sylwester]

Dear STKO,

I would like to study the effect of geometric nonlinearity using corotational formula on the deflection of a slab loaded at the center of the span with a node force.
I created two models
1. elastic material (corotational or linear)
2. nonlinear material Stell 02 and Asd Concrete 3D making a shell element that is 200 mm thick and has top and bottom reinforcement in two directions.

The fibers are:
1. Concrete 30 mm
2, Stell #6 spaced 200 mm =0.14
3. Stell #6 spaced 200 mm =0.14
4. Concrete 136 mm
5, Stell #6 spaced 200 mm =0.14
6. Stell #6 spaced 200 mm =0.14
7. Concrete 30 mm

Should I include the diameter of the reinforcement in the total thickness of the shell ? Now the concrete itself has 196 mm.

I also wanted to make sure I understood defining the layers of the fiber element correctly. Assuming, for example, that the bottom reinforcement was #16 every 150 mm, would I have to change positions 5 and 6? When do we know if a particular layer is on top or bottom?



In the middle of the slab I created a control node in which I want to study the deflections depending on the increase of the concentrated force

1. In the first model i created a load control analysis at set the duration as my load factor. In the monitor i choosed pseudo time (it should simulate the increasing force) (the force at the control node is 1kN=1000N (my units are N/mm)

model 1.png (29.22 KiB) Viewed 846 times

2. In model 2, I wanted to apply pushdown analysis using the displacement method. In the monitor i used the same settings. My problem is that I do not know how to interpret the results of what is happening to my model. Displacements are increasing as in elastic analysis.

model 2.png (26.24 KiB) Viewed 846 times

The crack plot shows ad the end cracks only in the middle

cracks.png (398.36 KiB) Viewed 846 times

, but in the step 17 its looks good. (why ??)

cracks 2.png (522.18 KiB) Viewed 846 times

Next i have general questions for Asd 3D concrete model. I am mainly analyzing vertically loaded slabs, is this constitutive model suitable for this or do you recommend another approach? On webinars this model used in loads in the plane of shell elements. I want to make multi-story slab-and-column structures after previous attempts on small models. Won't using the ASD 3D concrete model result in too much computational requirements (costs)?




Best regards

[Sylwester]

I made another calculation. In the fiber element I used elastic istrotropic for the concrete, but for steel 01 I defined minmax additionally. In response, the deflections increase infinitely. Why won't the bars rupture and stop the analysis?

[STKO Team]

1. Concrete 30 mm
2, Stell #6 spaced 200 mm =0.14
3. Stell #6 spaced 200 mm =0.14
4. Concrete 136 mm
5, Stell #6 spaced 200 mm =0.14
6. Stell #6 spaced 200 mm =0.14
7. Concrete 30 mm

This is fine, but the central part of concrete (136 mm) should be discretized with more layers, otherwise a single fiber is not able to capture bending

Should I include the diameter of the reinforcement in the total thickness of the shell ? Now the concrete itself has 196 mm.

I don't understand your point here. The Layered shell computes the total thickness as the sum of all layers

I also wanted to make sure I understood defining the layers of the fiber element correctly. Assuming, for example, that the bottom reinforcement was #16 every 150 mm, would I have to change positions 5 and 6? When do we know if a particular layer is on top or bottom?

Just remember this rule: the first fiber starts at the bottom, the last fibers is on top. the direction bottom -> top is dictated by the local Z axis of the shell

2. In model 2, I wanted to apply pushdown analysis using the displacement method. In the monitor i used the same settings. My problem is that I do not know how to interpret the results of what is happening to my model. Displacements are increasing as in elastic analysis.

Probably you cannot interpret it because you have displacement in the Y axis and loadFactor in the X axis. But it seems fine to me. From a displacement of 0 to a displacement of about 15, you have concrete cracking leading to the hardening in the pushdown curve. after that you reach the peak load probably due to onset of concrete crushing, and then you have softening due to progressive concrete crushing

Next i have general questions for Asd 3D concrete model. I am mainly analyzing vertically loaded slabs, is this constitutive model suitable for this or do you recommend another approach? On webinars this model used in loads in the plane of shell elements. I want to make multi-story slab-and-column structures after previous attempts on small models. Won't using the ASD 3D concrete model result in too much computational requirements (costs)?

Of course it's good for bending analyses, it's a general purpose 3D model

I made another calculation. In the fiber element I used elastic istrotropic for the concrete, but for steel 01 I defined minmax additionally. In response, the deflections increase infinitely. Why won't the bars rupture and stop the analysis?

If you used elastic concrete you will never see a complete failure. I

[Sylwester]

2. In model 2, I wanted to apply pushdown analysis using the displacement method. In the monitor i used the same settings. My problem is that I do not know how to interpret the results of what is happening to my model. Displacements are increasing as in elastic analysis.

Probably you cannot interpret it because you have displacement in the Y axis and loadFactor in the X axis. But it seems fine to me. From a displacement of 0 to a displacement of about 15, you have concrete cracking leading to the hardening in the pushdown curve. after that you reach the peak load probably due to onset of concrete crushing, and then you have softening due to progressive concrete crushing

I put the point force in the -Z global direction and in the displacement control setings I put dof=3 and target displacement -80 In the monitor settings Result Y axis are displacement (component Z), X axis PSeudo Time

[STKO Team]

I put the point force in the -Z global direction and in the displacement control setings I put dof=3 and target displacement -80 In the monitor settings Result Y axis are displacement (component Z), X axis PSeudo Time

Ok so it makes sense.
In the Y axis you have the displacement of the control point. It's negative as you imposed.
In the X axis you have the load multiplier. It's positive because your reference load is already negative.