What's wrong with my integration to calculate section properties

[AH_10884969]

I am developing a sheet to calculate section properties of steel sections using Mathcad Prime 10, however I find the integration gives zero value for web thickness less than a number for my specific example. 

see below screenshot and attached file. The Ay gives correct area, however the Ax doesn't. I have tried different values for tw which gives a correct result when it is larger than a certain number. For example in the I section if changed to 30mm, the integral gives correct answer. 

Appreciate any help please. 

[LucMeekes]

What is a right result, and what is wrong? It would be nice if you specify what you expect (versus what you get).

Your definition:

is overlapping.

The first row sets a value when -0.29m < x < 0.29 m and the last row sets a value when -0.77m < x< 0.77m.And the two middle rows specify the same range. So you get:

Is that intentional?

Success!
Luc

[AH_10884969]

The formula and the integral calculate the area of the steel section below. The total area should be 202550mm2, however the formula calculates it 141800 which basically the total flange areas. The web area is not calculated (second and third rows). 

I don't intend to have it overlapped, I am just unsure how to do it. 

[terryhendicott]

Hi,

Try this method of calculating section properties.  Starts with definition of the section by xy coordinates

Cheers

Terry

[terryhendicott · Accepted solution]

[AH_10884969]

Thanks Terry, that looks like to be the answer I am looking. 

Is there a way to use integral for the calcuations?

[terryhendicott]

Hi,

Example provided by you shows you can use integral but why complicate a simpler solution.

Have been using the generic section calculator since Mathcad 6 it works fine

Cheers

Terry

[AH_10884969]

Thank, yes, your solution looks to be simpler and easier to work with.

[AH_10884969]

Hi Terry, 

I wonder how you can add torsional and warping to the calculations. Have you tried calculating them using your method?

I have made some changes to the a plot which showed a very long line when a was 90 or zero degrees. 

[terryhendicott]

I wonder how you can add torsional and warping to the calculations. Have you tried calculating them using your method?

For torsional calculations I use a commercial FEM called "Strand 7" in most of the world but "Strauss 7" in Europe.  It is possible to enter 2D plate elements to make up a cross section in 2D and use this to get section capacities for torsional calculations or I get the values from tables produced by manufacturers..

[terryhendicott]

Found an old file calculates J and Cw

[vnamboodheri]

Hello @AH_10884969, 

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