The Pantheon Dome and its Amazing Structure! With Linda Seymour PhD

The Pantheon in Rome is a breathtaking space! At 2,000 years old, it’s also the world’s largest unreinforced concrete dome! So how has it lasted so long?
I’ll show you around the Pantheon, explain how domes work (and how much the Pantheon is a full structural dome), and Linda Seymour provides detail on Roman concrete. Linda did her PhD at MIT on ancient Roman concrete and we both work at SGH in Boston so it’s great to have her be part of this!
I'm Paul Kassabian. I'm a structural engineer and a Principal at SGH in Boston, MA. I taught graduate students at MIT for nine years, Harvard's Graduate School of Design (GSD) for five years and am currently teaching at RISD (Fall 2023). These are videos based on my structural design projects and years of teaching structures to students.
MUSIC:
Note: I chose music with instruments that existed in Roman times (harp and voice)
I have purchased a license for use from Pond5.com and the item ID number is 66320483.
Pond5's Royalty-Free License Agreement: www.pond5.com/legal/license
Publisher: Taylor Brook Music. Composer: Taylor Brook. PRO: SOCAN IPI#: 602881067
Title: Spiritual Harp and Choir.
License : Individual License for Commercial Use.

[@treecrusher]

Would love a longer video on this!

[@distant._.]

I love domes. I don’t have the Pantheon, but was able to build a wooden 3’ diameter rhombic triacontahedron to use as a “chandelier” in a modern built barn/shed. Awesome content thank you for all of your efforts!

[@PaulKassabian]

You're welcome!

[@thalesbastos400]

Thank you for the info and dedication!

[@JasonGerroll]

Linda, Paul - great video. Thank you for putting together.

[@PaulKassabian]

Thanks Jason!!! Good to hear from you

[@StereoSpace]

They made the walls thick. Exactly how thick they would have to work out. That's what fascinates me here. Did they build scale models, larger and larger, to see if the structural mechanics scaled up? I'm curious how they worked out what is sufficient to carry the loads. They built domed baths too, so I wonder if they developed a formula that gave them a ratio of dome size to wall thickness, something practical/empirical like that.

[@Jabmateh8]

Thanks Paul! Great video!

[@PaulKassabian]

Glad you liked it!

[@deborahlee8312]

Thank you Mr. Kassabian and Dr. Seymour for this great video! I just used it in my middle school engineering tech class connecting our lessons on materials, shapes, and forces. It was a perfect segway into their iconic structure research project.

[@PaulKassabian]

That’s great! Also sounds like you’re teaching an amazing course!

[@MikeAG333]

Imagine what they might have achieved if they had thought to rivet iron together to form a band all around the base of a dome.

[@schoolofducttape]

Loved the form on this one! Breaking down one structure at a time is golden to me! I link to you whenever I make something structural, love the content! What are some abnormal building materials you find interesting?

[@PaulKassabian]

Thanks and I’m lucky to have designed, and designing, with lots of materials…bamboo, mass timber, 3d printed glass/steel/concrete, the new carbon/glass frp pavilion at MIT, and recently structural stone…I love working to bring more variety of materials to our built environment…

[@schoolofducttape]

@@PaulKassabian bamboo is super cool! Too bad it's expensive in the USA

[@olgajoachimosmundsen4647]

Why does the hoop-forces transition from compression into tension? As a person with almost zero knowledge, but great interest in engineering I've watched most of your videos but struggle to really get the lesson home.

[@PaulKassabian]

Good question because it's much easier to picture/see the bottom of a dome wanting to spread outwards as it flattens...what happens at the top is less intuitive but is fully real...one way to picture it is that, as a dome flattens (and really picture it flattening out), the bottom has space to spread out but the top is trying to all move towards the center where there is no space, hence compression. The common physical experiment is to take half an orange and scoop out the fruit so you have a dome then shove down on it...have fun!