MIDAS Civil Plane Strain Element
Question:
There is a bug in the thickness calculations for plain strain elements when used with customary units. Consider file attached and perform query for Element 3002. Area is 9.998 sf, reported weight is 4.10 kips. Unit weight is 125 lbs/ft3, therefore expected weight for a 1-ft wide strip is 9.998 x 0.125 = 1.25 kips. The MIDAS result is off by a factor of 4.1/1.25 = 3.28, which is exactly the conversion from feet to meters. I suspect that the program uses 1 m internally regardless of unit setting. Stresses are reported correctly, the problem only occurs for reaction forces and weights.
Answer:
There is a bug in the thickness calculations for plain strain elements when used with customary units. Consider file attached and perform query for Element 3002. Area is 9.998 sf, reported weight is 4.10 kips. Unit weight is 125 lbs/ft3, therefore expected weight for a 1-ft wide strip is 9.998 x 0.125 = 1.25 kips. The MIDAS result is off by a factor of 4.1/1.25 = 3.28, which is exactly the conversion from feet to meters. I suspect that the program uses 1 m internally regardless of unit setting. Stresses are reported correctly, the problem only occurs for reaction forces and weights.
Answer:
Hi,
Thank you for your report. At the time this element type was implemented, the developers thought that there is no need to define the thickness of plane strain element, but now they agree it is not always correct. As you found out, the reactions due to self weight and element weight table do not make sense. They have decided to improve this. Rather than fixing the thickness of element as 1 m or 1 ft, we want to change the program so that the user can define the thickness of the elements with respect to the user-defined unit setting.
They said this improvement cannot be done in the current version and it will be done in the upcoming release. Hope this is acceptable for you.
Regards,
DK Lee
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