Update steelsections.py to create bulb flat

[zmpulse]

Update steelsections.py to create bulb flat

[robbievanleeuwen]

@zmpulse there are some comments in your code which confuse me:

dzero = ((c + t * 0.5 - r - t * 0.5) ** 2 + (b - r - b + d) ** 2) ** 0.5
# build radius
"""
to be update to include small radius on all sharp edge
to be update for tangence of the oblic line :
points.append([(r**2)/(dzero**2)*(t * 0.5)+r/(dzero**2)*((dzero**2)-(r**2))**0.5*(d-b),
              r**2/dzero**2*(b-d)+r/dzero**2*(dzero**2-r**2)**0.5*(t*0.5)])
points.append([(r**2)/(dzero**2)*(t * 0.5)-r/(dzero**2)*((dzero**2)-(r**2))**0.5*(d-b),
              r**2/dzero**2*(b-d)-r/dzero**2*(dzero**2-r**2)**0.5*(t*0.5)])"""

Also dzero isn't currently being used. Is the implementation complete?

[robbievanleeuwen]

@zmpulse could you please clarify how the dimensions work? See below code (I have shifted the section so the bottom left corner is at (0, 0):

from sectionproperties.pre.library.steel_sections import bulb_section

geometry = bulb_section(d=250, d_b=30, b=50, t=12, r=10, n_r=16).shift_section(6)
geometry.plot_geometry()

This generates the following figure which I have marked up:

These dimensions do not seem to align with the dimensions I have provided. Further there are some sharp transitions between straight lines and radii which do not look right. Are you able to comment on these?

[robbievanleeuwen]

Hi @zmpulse wondering if you are still interested in working on this? If not, I will close this PR.

[zmpulse]

Hi Robbie,
I have followed the convention ISO code for bulb flat and vendor.

So the full width of the bulb is at web thickness and bulb width. So in our case 50mm+12mm=62mm so it is ok.
For the small radius you are rigth on all sharp edge there is a small radius. (mentionned in the comments """to be update to include small radius on all sharp edge""").
For the sharp edge mention on the tangential line I will cross scheck it.

Thanks Robbie

[zmpulse]

I have found the width and depth of bulb that you used lead to an angle out of the standard because they don't respect the 30° angle of profile.

The parameter are not respecting this so it generate sharp edge at tangential line.

So if we go one step forward we should be able to skip the bulb width value because it is strainghtly link to bulb height.

[robbievanleeuwen]

Hi @zmpulse, thanks for providing the above diagrams, this makes sense.

I agree that the bulb width should be removed as it overconstrains the dimensions.

Are you able to make the above change to the PR and I will review and merge?

Thanks :)

[zmpulse]

done I will implement it now in the code

[zmpulse]

it is made:
if d_b == float: d_b = r * np.cos(np.pi / 3) / np.cos(np.pi / 6) + r + c * np.tan(np.pi / 6)