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[robbievanleeuwen]

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[ahmetanildindar]

Dear @robbievanleeuwen,
This is a very good repository for whom intending to foster the ideas and efforts in analyzing the RC section properties. I'll share the repo to my students so that we can support the codes in terms of development and examples.

All the best from Istanbul.

++Ahmet Anil Dindar

[robbievanleeuwen]

Hi @ahmetanildindar thanks for the kind words! Keen to hear any feedback you or your students have with concretepropeties!

[afugur]

hi robbie,

First of all, very nice work. I have a question for you. I want to assign nonlinear material to the inner region of a section with a concrete cover and linear material to the outer region. Is there a way to do this?

I tried this

conc_linear = Concrete(
    name="Linear Concrete",
    density=2.4e-6,
    stress_strain_profile=ssp.ConcreteLinear(
        elastic_modulus=35e3, ultimate_strain=0.0035
    ),
    ultimate_stress_strain_profile=ssp.BilinearStressStrain(
        compressive_strength=40,
        compressive_strain=0.00175,
        ultimate_strain=0.0035,
    ),
    alpha_squash=0.85,
    flexural_tensile_strength=3.5,
    colour="red",
)

conc_nonlinear = Concrete(
    name="Non-Linear Concrete",
    density=2.4e-6,
    stress_strain_profile=ssp.EurocodeNonLinear(
        elastic_modulus=35e3,
        ultimate_strain=0.0035,
        compressive_strength=40,
        compressive_strain=0.0023,
        tensile_strength=3.5,
        tension_softening_stiffness=10e3,
    ),
    ultimate_stress_strain_profile=ssp.BilinearStressStrain(
        compressive_strength=40,
        compressive_strain=0.00175,
        ultimate_strain=0.0035,
    ),
    alpha_squash=0.85,
    flexural_tensile_strength=3.5,
    colour="blue",
)

steel_ep = Steel(
    name="Steel - Elastic-Plastic",
    density=7.85e-6,
    stress_strain_profile=ssp.SteelElasticPlastic(
        yield_strength=500,
        elastic_modulus=200e3,
        fracture_strain=0.05,
    ),
    colour="grey",
)

col = rectangular_section(d=350, b=600,material=conc_nonlinear)
col1 = rectangular_section(d=450, b=700,material=conc_linear).align_center(align_to=col)

col2 = col1 + col
# add bars to column
geom = add_bar_rectangular_array(
    geometry=col2,
    area=450,
    material=steel_ep,
    n_x=6,
    x_s=492 / 5,
    n_y=3,
    y_s=121,
    anchor=(54, 54),
    exterior_only=True,
)

then I got this.

Is it true ?

[connorferster]

Hi @afugur,

From the plot, the section looks good however it seems that you have overlapping regions which are not permitted in concreteproperties. See below.

col = rectangular_section(d=350, b=600,material=conc_nonlinear)
col1 = rectangular_section(d=450, b=700,material=conc_linear).align_center(align_to=col)

col2 = col1 + col # Ambiguity created here because these sections overlap

The plot we see is showing the materials as they are understood based on the assigned control points in each region however if I run the following after running the script you provided:

I can see that the center concrete geometry is assigned two control points (0 and 1). This shows that there are overlapping regions.

To prevent overlapping regions, we need to use the following modelling technique:

col2 = (col1 - col) + col

Then the control points of the concrete regions are assigned correctly and there are no more overlapping regions:

You can read more about this, here:
https://sectionproperties.readthedocs.io/en/latest/rst/advanced_geom.html

[afugur]

Thank you so much.

[robbievanleeuwen]

Thanks @connorferster great explanation!

@afugur you should also get a warning if you try to create a ConcreteSection object with geometry that has overlapping regions. Running your code I get this warning:

UserWarning: The provided geometry contains overlapping regions, results may be incorrect.

Using col2 = (col1 - col) + col removes this warning.

[afugur]

Thanks @robbievanleeuwen,

I saw the "UserWarning: The provided geometry contains overlapping regions, results may be incorrect." problem. Because of that I wanted to know true way :)