This case study compares stress SX in volume and shell elements, which are supported in statically determinate
condition, as well as statically indeterminate condition.
In Case 1 There are two models of dimension lxbxh=10x2x1m created in volume HX8M and shell QTS4 element.
The supported lines are assumed at the bottom of both models as shown in figure below. Values of stress SX in kPa
are in focus.
Case 1: Statically determinate support of volume and shell elements, stress SX in kPa.
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The above ratio 1.009 shown that the stress SXTop from
volume element is agreed with the shell element,
considered the centre nodes.
The same result is also obtained for SXBot.
Element mesh 1x1m has been assigned to both elements.
For volume HX8M it is 1x1x0.5m where 0.5m is the thickness
in element vertical x-axes (element axes is not shown).
Further, the shell result is compared to beam as shown to the right. The shell-to-beam-ratio is here 0.98. Note that shell element has two-axes bending condition where as the beam element is a single line mesh with one-axes bending condition.
In Case 3 there are two models of dimension lxbxh=10x10x1m created in volume HX8M and shell QTS4 elements.
All four lines at the bottom of the models are assumed to support (statically indeterminate) with stiffness UX, UY,
UZ, RX, RY and RZ. Values of stress SX in kPa are in focus.
Case 3 below shows free rotational support, where the translational support are assumed 500kN/m/m in all three directions, both of models (stiffness/unit length). It seems that the ratio of stress SXTop is 1.005 between the volume and shell model, and the ratio for SXBot is 1.001, at the centre nodes.
Case 3: Statically determinate support with free rotation, stress SX in kPa
Case 4 shows fixed rotational supported RX=RY=RZ=500kNm/m compared to case 3. The ratio for SXTop is 1.214,
and SXBot is 1.202. It seems that the stresses SXTop and SXBot are keep unchanged from Case 3 to 4 for the volume
elements. On the other hand, the rotational supports has reduced stress in the shell elements to about 82% of values
for the volume elements.
Case 4: Statically determinate support fixed rotation, stress SX in kPa