Help！！！How to build a circle section in a rectangular sectio

[andy0071]

I wanderto build a rectangular section in which I want to put a circle section in different kind of material. But the OpenSees don't have a command of cut,so how to build a circle section in a rectangular section???

I have try to build a rectangular section first and circle above and a third circle setion with same strain and negative stress of the ractangular section to offset the double of the circle setion.... with the concrete 01material. I try to build first and second section in same kind of material thrid in negetive number of the same material but is different from all ractangular section wiht the material positive number~~~~%>_<%


anyone anyanswer will be Ok!
Thanks~

[vesna]

Here is what you can do:

1. define the circular portion of the section using "patch circ" command
2. define four rectangular portions of the section using "patch rect" command. These four patches should form hollow rectangular section that encompasses the circular section.
3. the rest of the section shall be define with "fiber" command defining the fibers one by one.

[andy0071]

Thank you vesna,your suggestion is feasible and I believe is the only way now to build this kind of section. Perhaps we should have the "cut" command in OpenSees someday~~

I wander to build it using your first and second suggestions but for the rest of the section between the rectangular frame outside and the circle inside I want to build some small rectangular sections with one long edge and one small dege which is small enough and obey the quadratic equation of the circle section inside to locate all the rectangular section. These section will get the place left for fiber command is small enough to build and is also limited and accurate.

But I wander to know that how big, i mean the area left for each fiber section is proper which will make it more accurate but not too hard to get convergence.

Thank you for your answer, it's really helpful!!!

[vesna]

I'm sorry but I do not understand your question. Try to re-elaborate on it.

[andy0071]

~~(╯﹏╰)b,sorry herhaps it's my fault not describe it clearly.

I wander to build the compound section in 4 kinds of parts

first, the inside circle section and make the dimension i need.

second, four outside frame with rectangular sections, which is located outside the circle section in top, bottomand, right and left and the fringes is tangency with the circle inside.

Third, in order to fill the place between the sections above and make it easy to get convergence, i use lots of small rectangular sections to fill it but not used the fiber here. Like the differential and integral calculus, all the small sections are putted in horizontal direction one by one and have one side long, which is from the fringe of the first section to the fringe of the second section, and one side short herhaps 0.01mm or 0.1mm.Each one is little smaller than the one in the front of it. All the rectangular section is located obeyed the quadratic equation of the circle section inside. So nearly all the place between the first and sectond section is filled but there are still some small place like triangle sections is left.

There i wander to use the fiber section to fill these triangle section to make it accurate, of course, one side of the triangle is not a straight line but a curve.These fiber section is the fourth sections. And the dimension of area of these triangle secions depend on the short side of the third kind of secions and the difference between these sections in the long side.
But the size of the fourth section could not be too big to be accurate neither too small to get convergence.

Now here is my question: What size of the fourth secion is proper? 0.1mm×0.1mm÷2 or 0.01mm×0.01mm÷2 or something else？

Thank you for your answer~\(^o^)/~

[vesna]

It depends on the size of your section. However, 0.1mm sounds too small to me. I would not go below 1mm.

[andy0071]

Thank you for your answer and i get what i want. Thanks again~~~