# Shell and solid model at large thickness ratio

**URL:** <https://calculix.discourse.group/t/shell-and-solid-model-at-large-thickness-ratio/2421>\
**Category:** Uncategorized\
**Created:** [September 28, 2024, 5:29am UTC](https://calculix.discourse.group/t/shell-and-solid-model-at-large-thickness-ratio/2421 "2024-09-28T05:29:08Z")\
**Posts on this page:** 7\
**Page:** 1

<div class="post-metadata">

**Author:** ![xyont](https://yyz2.discourse-cdn.com/free1/user_avatar/calculix.discourse.group/xyont/32/3553_2.png) [@xyont](https://calculix.discourse.group/u/xyont)\
**Post date:** [September 28, 2024, 5:29am UTC](https://calculix.discourse.group/t/shell-and-solid-model-at-large-thickness-ratio/2421/1 "2024-09-28T05:29:08Z")

</div>

hi, i’m modeling a shell with large thickness to spans ratio. It’s a simple cantilever beam with end loads at top surfaces, one by one ratio needed to concerning diagonal compression strut actions, layering by composite options for refinement also. However, the result shown discrepancy compared to solid models (attached). Is there some explanation related to face load of shell element during expansion? thank you.

 ![2024-09-28 12_31_04-CalculiX GraphiX](https://global.discourse-cdn.com/free1/uploads/calculix/original/2X/1/1e4d62ea83b289643a720d5e53bc4416945c93fe.png)

 ![2024-09-28 12_19_09-CalculiX GraphiX](https://global.discourse-cdn.com/free1/uploads/calculix/original/2X/1/13721cfd6062483d56417e642826dc6ccc1e817f.png)

 ![2024-09-28 12_19_31-CalculiX GraphiX](https://global.discourse-cdn.com/free1/uploads/calculix/original/2X/8/8352885b53a793ab34622372b405d0071663f07c.png)

 ![2024-09-28 12_19_59-CalculiX GraphiX](https://global.discourse-cdn.com/free1/uploads/calculix/original/2X/d/de8bb847c8782bcc314cdbee810255dd2c9d00c1.png)

 ![2024-09-28 12_20_45-CalculiX GraphiX](https://global.discourse-cdn.com/free1/uploads/calculix/original/2X/b/bb8fa38c2a2c5df65de017d68ac82b9b51ea3f91.png)

---

<div class="post-metadata">

**Author:** ![xyont](https://yyz2.discourse-cdn.com/free1/user_avatar/calculix.discourse.group/xyont/32/3553_2.png) [@xyont](https://calculix.discourse.group/u/xyont)\
**Post date:** [September 29, 2024, 8:50pm UTC](https://calculix.discourse.group/t/shell-and-solid-model-at-large-thickness-ratio/2421/2 "2024-09-29T20:50:15Z")

</div>

attached input file for coarse mesh.

 ![2024-09-30 03_39_46-CalculiX GraphiX](https://global.discourse-cdn.com/free1/uploads/calculix/original/2X/c/c2b9567fc921f9a5f2b9da096ff04739adbfb8b3.png)

```auto
*Heading
Shell element (composite) surface load
*Node
1, 0.00000000E+000, 0.00000000E+000, 5.00000000E+001
2, 9.00000000E+001, 0.00000000E+000, 5.00000000E+001
3, 9.00000000E+001, 1.00000000E+002, 5.00000000E+001
4, 0.00000000E+000, 1.00000000E+002, 5.00000000E+001
5, 1.00000000E+002, 1.00000000E+002, 5.00000000E+001
6, 1.00000000E+002, 0.00000000E+000, 5.00000000E+001
7, 4.50000000E+001, 0.00000000E+000, 5.00000000E+001
8, 2.25000000E+001, 0.00000000E+000, 5.00000000E+001
9, 6.75000000E+001, 0.00000000E+000, 5.00000000E+001
10, 9.00000000E+001, 5.00000000E+001, 5.00000000E+001
11, 9.00000000E+001, 2.50000000E+001, 5.00000000E+001
12, 9.00000000E+001, 7.50000000E+001, 5.00000000E+001
13, 4.50000000E+001, 1.00000000E+002, 5.00000000E+001
14, 6.75000000E+001, 1.00000000E+002, 5.00000000E+001
15, 2.25000000E+001, 1.00000000E+002, 5.00000000E+001
16, 0.00000000E+000, 5.00000000E+001, 5.00000000E+001
17, 0.00000000E+000, 7.50000000E+001, 5.00000000E+001
18, 0.00000000E+000, 2.50000000E+001, 5.00000000E+001
19, 9.50000000E+001, 1.00000000E+002, 5.00000000E+001
20, 9.50000000E+001, 0.00000000E+000, 5.00000000E+001
21, 1.00000000E+002, 5.00000000E+001, 5.00000000E+001
22, 1.00000000E+002, 2.50000000E+001, 5.00000000E+001
23, 1.00000000E+002, 7.50000000E+001, 5.00000000E+001
24, 4.50000000E+001, 5.00000000E+001, 5.00000000E+001
25, 2.25000000E+001, 5.00000000E+001, 5.00000000E+001
26, 4.50000000E+001, 2.50000000E+001, 5.00000000E+001
27, 4.50000000E+001, 7.50000000E+001, 5.00000000E+001
28, 6.75000000E+001, 5.00000000E+001, 5.00000000E+001
29, 9.50000000E+001, 5.00000000E+001, 5.00000000E+001
80, 1.00000000E+002, 2.50000000E+002, 1.00000000E+002
81, 1.00000000E+002, 1.50000000E+002, 1.00000000E+002
82, 0.00000000E+000, 2.50000000E+002, 1.00000000E+002
83, 9.00000000E+001, 2.50000000E+002, 1.00000000E+002
84, 9.00000000E+001, 1.50000000E+002, 1.00000000E+002
85, 0.00000000E+000, 1.50000000E+002, 1.00000000E+002
86, 1.00000000E+002, 2.50000000E+002, 0.00000000E+000
87, 9.00000000E+001, 2.50000000E+002, 0.00000000E+000
88, 9.00000000E+001, 1.50000000E+002, 0.00000000E+000
89, 1.00000000E+002, 1.50000000E+002, 0.00000000E+000
90, 0.00000000E+000, 1.50000000E+002, 0.00000000E+000
91, 0.00000000E+000, 2.50000000E+002, 0.00000000E+000
92, 1.00000000E+002, 2.00000000E+002, 1.00000000E+002
93, 1.00000000E+002, 1.75000000E+002, 1.00000000E+002
94, 1.00000000E+002, 2.25000000E+002, 1.00000000E+002
95, 4.50000000E+001, 2.50000000E+002, 1.00000000E+002
96, 6.75000000E+001, 2.50000000E+002, 1.00000000E+002
97, 2.25000000E+001, 2.50000000E+002, 1.00000000E+002
98, 9.50000000E+001, 2.50000000E+002, 1.00000000E+002
99, 9.50000000E+001, 1.50000000E+002, 1.00000000E+002
100, 4.50000000E+001, 1.50000000E+002, 1.00000000E+002
101, 2.25000000E+001, 1.50000000E+002, 1.00000000E+002
102, 6.75000000E+001, 1.50000000E+002, 1.00000000E+002
103, 0.00000000E+000, 2.00000000E+002, 1.00000000E+002
104, 0.00000000E+000, 2.25000000E+002, 1.00000000E+002
105, 0.00000000E+000, 1.75000000E+002, 1.00000000E+002
106, 9.00000000E+001, 2.00000000E+002, 1.00000000E+002
107, 9.00000000E+001, 1.75000000E+002, 1.00000000E+002
108, 9.00000000E+001, 2.25000000E+002, 1.00000000E+002
109, 1.00000000E+002, 2.50000000E+002, 5.00000000E+001
110, 1.00000000E+002, 2.50000000E+002, 7.50000000E+001
111, 1.00000000E+002, 2.50000000E+002, 2.50000000E+001
112, 9.00000000E+001, 2.50000000E+002, 5.00000000E+001
113, 9.00000000E+001, 2.50000000E+002, 7.50000000E+001
114, 9.00000000E+001, 2.50000000E+002, 2.50000000E+001
115, 9.50000000E+001, 2.50000000E+002, 0.00000000E+000
116, 9.00000000E+001, 1.50000000E+002, 5.00000000E+001
117, 9.00000000E+001, 1.50000000E+002, 7.50000000E+001
118, 9.00000000E+001, 1.50000000E+002, 2.50000000E+001
119, 9.00000000E+001, 2.00000000E+002, 0.00000000E+000
120, 9.00000000E+001, 1.75000000E+002, 0.00000000E+000
121, 9.00000000E+001, 2.25000000E+002, 0.00000000E+000
122, 1.00000000E+002, 1.50000000E+002, 5.00000000E+001
123, 1.00000000E+002, 1.50000000E+002, 7.50000000E+001
124, 1.00000000E+002, 1.50000000E+002, 2.50000000E+001
125, 9.50000000E+001, 1.50000000E+002, 0.00000000E+000
126, 1.00000000E+002, 2.00000000E+002, 0.00000000E+000
127, 1.00000000E+002, 1.75000000E+002, 0.00000000E+000
128, 1.00000000E+002, 2.25000000E+002, 0.00000000E+000
129, 0.00000000E+000, 1.50000000E+002, 5.00000000E+001
130, 0.00000000E+000, 1.50000000E+002, 7.50000000E+001
131, 0.00000000E+000, 1.50000000E+002, 2.50000000E+001
132, 4.50000000E+001, 1.50000000E+002, 0.00000000E+000
133, 2.25000000E+001, 1.50000000E+002, 0.00000000E+000
134, 6.75000000E+001, 1.50000000E+002, 0.00000000E+000
135, 0.00000000E+000, 2.50000000E+002, 5.00000000E+001
136, 0.00000000E+000, 2.50000000E+002, 7.50000000E+001
137, 0.00000000E+000, 2.50000000E+002, 2.50000000E+001
138, 4.50000000E+001, 2.50000000E+002, 0.00000000E+000
139, 6.75000000E+001, 2.50000000E+002, 0.00000000E+000
140, 2.25000000E+001, 2.50000000E+002, 0.00000000E+000
141, 0.00000000E+000, 2.00000000E+002, 0.00000000E+000
142, 0.00000000E+000, 2.25000000E+002, 0.00000000E+000
143, 0.00000000E+000, 1.75000000E+002, 0.00000000E+000
144, 9.50000000E+001, 2.00000000E+002, 1.00000000E+002
145, 4.50000000E+001, 2.00000000E+002, 1.00000000E+002
146, 4.50000000E+001, 1.75000000E+002, 1.00000000E+002
147, 2.25000000E+001, 2.00000000E+002, 1.00000000E+002
148, 4.50000000E+001, 2.25000000E+002, 1.00000000E+002
149, 6.75000000E+001, 2.00000000E+002, 1.00000000E+002
150, 9.50000000E+001, 2.50000000E+002, 5.00000000E+001
151, 9.00000000E+001, 2.00000000E+002, 5.00000000E+001
152, 9.00000000E+001, 2.00000000E+002, 7.50000000E+001
153, 9.00000000E+001, 1.75000000E+002, 5.00000000E+001
154, 9.00000000E+001, 2.00000000E+002, 2.50000000E+001
155, 9.00000000E+001, 2.25000000E+002, 5.00000000E+001
156, 9.50000000E+001, 1.50000000E+002, 5.00000000E+001
157, 1.00000000E+002, 2.00000000E+002, 5.00000000E+001
158, 1.00000000E+002, 1.75000000E+002, 5.00000000E+001
159, 1.00000000E+002, 2.00000000E+002, 7.50000000E+001
160, 1.00000000E+002, 2.00000000E+002, 2.50000000E+001
161, 1.00000000E+002, 2.25000000E+002, 5.00000000E+001
162, 9.50000000E+001, 2.00000000E+002, 0.00000000E+000
163, 4.50000000E+001, 1.50000000E+002, 5.00000000E+001
164, 2.25000000E+001, 1.50000000E+002, 5.00000000E+001
165, 4.50000000E+001, 1.50000000E+002, 7.50000000E+001
166, 4.50000000E+001, 1.50000000E+002, 2.50000000E+001
167, 6.75000000E+001, 1.50000000E+002, 5.00000000E+001
168, 4.50000000E+001, 2.50000000E+002, 5.00000000E+001
169, 6.75000000E+001, 2.50000000E+002, 5.00000000E+001
170, 4.50000000E+001, 2.50000000E+002, 7.50000000E+001
171, 4.50000000E+001, 2.50000000E+002, 2.50000000E+001
172, 2.25000000E+001, 2.50000000E+002, 5.00000000E+001
173, 0.00000000E+000, 2.00000000E+002, 5.00000000E+001
174, 0.00000000E+000, 2.25000000E+002, 5.00000000E+001
175, 0.00000000E+000, 2.00000000E+002, 7.50000000E+001
176, 0.00000000E+000, 2.00000000E+002, 2.50000000E+001
177, 0.00000000E+000, 1.75000000E+002, 5.00000000E+001
178, 4.50000000E+001, 2.00000000E+002, -1.42108547E-014
179, 2.25000000E+001, 2.00000000E+002, -7.10542736E-015
180, 4.50000000E+001, 1.75000000E+002, -7.10542736E-015
181, 4.50000000E+001, 2.25000000E+002, -7.10542736E-015
182, 6.75000000E+001, 2.00000000E+002, -7.10542736E-015
183, 9.50000000E+001, 2.00000000E+002, 5.00000000E+001
184, 4.50000000E+001, 2.00000000E+002, 5.00000000E+001
185, 4.50000000E+001, 2.00000000E+002, 7.50000000E+001
186, 4.50000000E+001, 1.75000000E+002, 5.00000000E+001
187, 2.25000000E+001, 2.00000000E+002, 5.00000000E+001
188, 4.50000000E+001, 2.00000000E+002, 2.50000000E+001
189, 4.50000000E+001, 2.25000000E+002, 5.00000000E+001
190, 6.75000000E+001, 2.00000000E+002, 5.00000000E+001
*Element, Type=C3D20R, Elset=Solid_part-1
21, 106, 83, 80, 92, 151, 112, 109, 157, 108, 98, 94, 144, 155, 150, 161,
183, 152, 113, 110, 159
22, 151, 112, 109, 157, 119, 87, 86, 126, 155, 150, 161, 183, 121, 115, 128,
162, 154, 114, 111, 160
23, 84, 106, 92, 81, 116, 151, 157, 122, 107, 144, 93, 99, 153, 183, 158,
156, 117, 152, 159, 123
24, 116, 151, 157, 122, 88, 119, 126, 89, 153, 183, 158, 156, 120, 162, 127,
125, 118, 154, 160, 124
25, 145, 100, 85, 103, 184, 163, 129, 173, 146, 101, 105, 147, 186, 164, 177,
187, 185, 165, 130, 175
26, 184, 163, 129, 173, 178, 132, 90, 141, 186, 164, 177, 187, 180, 133, 143,
179, 188, 166, 131, 176
27, 95, 145, 103, 82, 168, 184, 173, 135, 148, 147, 104, 97, 189, 187, 174,
172, 170, 185, 175, 136
28, 168, 184, 173, 135, 138, 178, 141, 91, 189, 187, 174, 172, 181, 179, 142,
140, 171, 188, 176, 137
29, 106, 84, 100, 145, 151, 116, 163, 184, 107, 102, 146, 149, 153, 167, 186,
190, 152, 117, 165, 185
30, 151, 116, 163, 184, 119, 88, 132, 178, 153, 167, 186, 190, 120, 134, 180,
182, 154, 118, 166, 188
31, 83, 106, 145, 95, 112, 151, 184, 168, 108, 149, 148, 96, 155, 190, 189,
169, 113, 152, 185, 170
32, 112, 151, 184, 168, 87, 119, 178, 138, 155, 190, 189, 169, 121, 182, 181,
139, 114, 154, 188, 171
*Element, Type=S8R, Elset=Compound-1
1, 1, 16, 24, 7, 18, 25, 26, 8
2, 16, 4, 13, 24, 17, 15, 27, 25
3, 7, 24, 10, 2, 26, 28, 11, 9
4, 24, 13, 3, 10, 27, 14, 12, 28
5, 5, 21, 10, 3, 23, 29, 12, 19
6, 21, 6, 2, 10, 22, 20, 11, 29
*Nset, Nset=Node_Set-1
1, 4, 16, 17, 18
*Nset, Nset=Node_Set-2
82, 85, 90, 91, 103, 104, 105, 129, 130, 131, 135, 136, 137, 141, 142, 143, 
173, 174, 175, 176, 177
*Elset, Elset=Internal-1_Internal_Selection-1_Uniform_Pressure-2_S1
21, 23
*Elset, Elset=Internal-1_Internal_Selection-1_Uniform_Pressure-1_S1
5, 6
*Surface, Name=Internal_Selection-1_Uniform_Pressure-2, Type=Element
Internal-1_Internal_Selection-1_Uniform_Pressure-2_S1, S1
*Surface, Name=Internal_Selection-1_Uniform_Pressure-1, Type=Element
Internal-1_Internal_Selection-1_Uniform_Pressure-1_S1, S1
*Material, Name=Concrete
*Elastic
25000, 0.2
*Solid section, Elset=Solid_part-1, Material=Concrete
*Shell Section, Elset=Compound-1, Composite
50.,,Concrete
50.,,Concrete
*Step
*Static, Solver=Spooles
*Boundary
Node_Set-2, 1, 1, 0
Node_Set-2, 2, 2, 0
Node_Set-2, 3, 3, 0
** Name: Displacement_Rotation-2
*Boundary
Node_Set-1, 1, 1, 0
Node_Set-1, 2, 2, 0
Node_Set-1, 3, 3, 0
Node_Set-1, 5, 5, 0
*Dload
Internal-1_Internal_Selection-1_Uniform_Pressure-1_S1, P, 10
*Dload
Internal-1_Internal_Selection-1_Uniform_Pressure-2_S1, P1, 10
*Node file
RF, U
*El file
S, E, NOE
*End step

```

---

<div class="post-metadata">

**Author:** ![vicmw](https://avatars.discourse-cdn.com/v4/letter/v/6de8d8/32.png) [@vicmw](https://calculix.discourse.group/u/vicmw)\
**Post date:** [September 30, 2024, 4:06am UTC](https://calculix.discourse.group/t/shell-and-solid-model-at-large-thickness-ratio/2421/3 "2024-09-30T04:06:53Z")

</div>

Your solid model should be only a single element thick to compare to the shell.

Composite shells are still only solved as a single element for all layers together but with integration points at each layer and the per-layer elements are generated for the solution.

---

<div class="post-metadata">

**Author:** ![xyont](https://yyz2.discourse-cdn.com/free1/user_avatar/calculix.discourse.group/xyont/32/3553_2.png) [@xyont](https://calculix.discourse.group/u/xyont)\
**Post date:** [September 30, 2024, 7:15am UTC](https://calculix.discourse.group/t/shell-and-solid-model-at-large-thickness-ratio/2421/4 "2024-09-30T07:15:16Z")

</div>

try to understand by model as suggested, still shown discrepancy. Only one element trough thickness is similar in result between shell and solid model.

 ![2024-09-30 13_55_50-CalculiX GraphiX](https://global.discourse-cdn.com/free1/uploads/calculix/original/2X/e/e3f1f77cb440edfb979ecc047d1755f1adcd46d2.png)

 ![2024-09-30 14_00_04-CalculiX GraphiX](https://global.discourse-cdn.com/free1/uploads/calculix/original/2X/9/9f28ee5fe4b202661a2817907fab60a333303dde.png)

> [@vicmw](#):
>
> Composite shells are still only solved as a single element for all layers together…

but thanks for the hint, this may have consistent with another test of lowest stiffness in core layer.

---

<div class="post-metadata">

**Author:** ![vicmw](https://avatars.discourse-cdn.com/v4/letter/v/6de8d8/32.png) [@vicmw](https://calculix.discourse.group/u/vicmw)\
**Post date:** [September 30, 2024, 9:46am UTC](https://calculix.discourse.group/t/shell-and-solid-model-at-large-thickness-ratio/2421/5 "2024-09-30T09:46:53Z")

</div>

I’m guessing the discrepancy in the first picture, especially being stress, might be because of the extra integration points of composites. I wonder if using C3D20 instead of C3D20R would bring them a little closer?

---

<div class="post-metadata">

**Author:** ![xyont](https://yyz2.discourse-cdn.com/free1/user_avatar/calculix.discourse.group/xyont/32/3553_2.png) [@xyont](https://calculix.discourse.group/u/xyont)\
**Post date:** [September 30, 2024, 10:38am UTC](https://calculix.discourse.group/t/shell-and-solid-model-at-large-thickness-ratio/2421/6 "2024-09-30T10:38:21Z")

</div>

it seems to be right, two layer of composite shell (S8R) is similar with one layer of solid with unreduced integration (C3D20).

 ![2024-09-30 17_17_02-CalculiX GraphiX](https://global.discourse-cdn.com/free1/uploads/calculix/original/2X/6/603b80df12b548f4daa44983542b3a9f6ef37750.png)

 ![2024-09-30 17_17_19-CalculiX GraphiX](https://global.discourse-cdn.com/free1/uploads/calculix/original/2X/4/46c5629e20d1c5e03b5743eb6ea02b09bf602d33.png)

also, switching to transfer load by contact analysis with rigid part. Result shown discrepancy is not related to surface load of shell element with composite options.

 ![2024-09-30 16_46_44-CalculiX GraphiX](https://global.discourse-cdn.com/free1/uploads/calculix/original/2X/0/0248d0c349cc68baeea7cdd36363d044af37f9d8.png)

 ![2024-09-30 16_46_05-CalculiX GraphiX](https://global.discourse-cdn.com/free1/uploads/calculix/original/2X/4/4cfea3af4f5ecc17a973841082fd72a6d20d98bb.png)

---

<div class="post-metadata">

**Author:** ![xyont](https://yyz2.discourse-cdn.com/free1/user_avatar/calculix.discourse.group/xyont/32/3553_2.png) [@xyont](https://calculix.discourse.group/u/xyont)\
**Post date:** [October 1, 2024, 9:45pm UTC](https://calculix.discourse.group/t/shell-and-solid-model-at-large-thickness-ratio/2421/7 "2024-10-01T21:45:56Z")

</div>

it seems composite shell model needed to switch to in plane load cases to be comparable with solid ones. To my understanding, out of plane load models still can capture diagonal compression strut, but magnitude and distribution shown less accurate since only one element trough thickness being used by the solver, actually.

 ![2024-10-02 04_24_58-CalculiX GraphiX](https://global.discourse-cdn.com/free1/uploads/calculix/original/2X/9/9b3a512179d0268025fe8aacb36fa32214ab343a.png)

 ![2024-10-02 04_26_05-CalculiX GraphiX](https://global.discourse-cdn.com/free1/uploads/calculix/original/2X/2/2accca1c60853de364622f1b8fb087cfdcb98088.png)

 ![2024-10-02 04_26_44-CalculiX GraphiX](https://global.discourse-cdn.com/free1/uploads/calculix/original/2X/2/211f198c0fbf3718dda438665cab3295a7a138d7.png)

 ![2024-10-02 04_27_17-CalculiX GraphiX](https://global.discourse-cdn.com/free1/uploads/calculix/original/2X/6/6a915d752ac83063438fb685451d884b902b460b.png)

 ![2024-10-02 04_33_22-CalculiX GraphiX](https://global.discourse-cdn.com/free1/uploads/calculix/original/2X/c/c7cf5472de65c03deb68a6202d73e3f4a3e601bf.png)