3D MODEL OF A GROIN VAULT

[chiarina.gelati]

Hi everybody, 

i'm new to this forum, i'm writing here to ask your help for the modellation of an irregular groin vault for my thesis in Architecture.

The problem i found on my 3d modeling project is:

the groin vaults i have to model cover spaces that are not squared-plan but trapezioidal-plan. For that reason the border arches have different diameters and they aren’t parallel to aech other two by two. I saw many web tutorials but all of them are explaining how to model regular vaults and so they are not usefull for my situation. Furthermore my model has to be imported in a seismic analyzis program (Straus 7) and so it has to be realized as a full volum and not as a surface (exactly 30 cm of structural thickness); at last it has to be merged to the side walls because the final model has to be a single volume, as required by Straus 7.

As attached file a map showing the groin vaults structure (the dashed lines represent the projection of the diagonal arches and of the border arches).

Thank you in advance for your help, i really hope that someone could help me.

[kasperwuyts]

From what I gather, a groin vault is basically an intersection of two barrel vaults. In this case these barrel vaults are irregular. I would model an irregular barrel vault using 2 ellipses between opossite ends of the vault, and creating a loft between them. An irregular groin vault would then be an intersection of two of these lofts.

Check the sample to see if this is close to the shape you want (this is just the two lofts, you'll have to actually modify it quite a bit using the boolean tools to get an actual vault out of them.)

[chiarina.gelati]

Hi kasperwuyts, thank you for your reply! 

The model you sent me is correct and i think i could make the groin vault using the tools "union" (to merge the two loft), "slice" (to remove the bottom) and "shell" (to obtain the right thickness of my vault).

The problem is that i have the dimensions of the vault from the lower surface and i'm not able to go back to the size of the external surface.

For this reason i always started from the inner surface and then i tried (with no results) to give it the right thickness (i tried with extrude and offset but both the tools failed 'cause the first one generate surfaces that intersect themselves and the second one doesn't give a constant thickness to the vault).

So maybe your method can be better but i have to find the way to start from the external surface and obtain exactly the size of the vault that i have in the inner one. Do you have any ideas? 

I attached you the file with the diagonal arches of my vaults and my attempts to create the vault. 

Thank you so much, kind Regards

Chiara 

[kasperwuyts]

Hi Chiara

I'm struggling a bit to understand your terminology. I'm not exactly sure what you mean with inner surface, external surface, and lower surface. I'm assuming lower and inner just mean the bottom surface of your 30cm thick structure, and external means the upper surface?

By the way, there is a command called 'thicken' to turn a surface into a solid with constant thickness. It might not be your best option here however. I would go the solid route all the way.

Using the solid route however, i've found some problems with trying to use the boolean commands on my lofts. Might be too complex for them, although I'm quite surprised at that. i'll look into it this weekend.

[chiarina.gelati]

Hi Kasperwuyts, 

i'm sorry... it's quite difficult to explain the problem also in italian for me...i'm doing my best but it seems i'm not doing it well! 

However, you understood what i wanted to say...

I used "inner surface" and "lower surface" to identify what in italian we call "intradosso" (bottom surface of the thickness) and "external surface" to indicate the "estradosso" (upper surface of the thickness). I attached an image in order to make you understand. 

I was trying to use the tool "thicken" just this morning and it's reasonably good...the bottom surface matches with the "guide lines" of my map, but there is a problem with the upper surface at the crossover between the diagonals and the base (bottom of the vault). If you zoom the image i attached you can see it. This is a problem for me 'cause the program where i have to import my model crashes while it's trying to make the mash (there are too many points there) so i'm trying to solve it. 

I really hope you can help me.

Thank you so much. 

Regards 

Chiara

[chiarina.gelati]

I wanted to write "mesh" and not mash.