There may be times when you want to place a type of dome on top of a building, but you may not know how since the building is square or rectangular. Well, if you have this problem, or think you will in the future, then you'll want to brush up on your outstanding skills. Pendants are basically a construction device that will allow you to place a round dome on top of a square room or an elliptical shaped dome on top of a rectangular room.
The pendants are basically triangular segments and narrow to a point at the very bottom. The tops are spread out to create the base needed for the type of dome you want to use. This method was finally created after many years of using squinches in the corners of any room.
Pendants are usually intricately designed with many unique details and there are typically four of them for each dome. The purpose of the pendants is to make the dome appear to be suspended in the air, basically like a pendant, hence the word pendants. The four pendants create a visual story inside the dome and many people are left breathless or simply mesmerized when they enter and start looking around.
Dome geometry
The pendentives have been in the works since Roman times, but it was only in the Byzantine era that the structural intricacies were fully appreciated. It was at this time that they realized that the diameter of the dome used needed to be the same length as the diagonal part of the room. Back then, this wasn't so easy to understand or know, so it took a lot of hard work to figure out this problem and find the solution that worked best.
Before we discovered this, many of the support structures in domed buildings needed to be round. An excellent example of this would be the Pantheon in Rome. Of course, this limited the height of the domes as well as the widths.
What pendants do
Once the pendants are in place, they remove all external force from the weight of the dome. This weight goes to the four corners before flowing through the columns toward the foundation. Tall supporting walls aren't necessary when you use a pendant, so you don't have to worry about views being obscured. One of the best examples of a pendant is the Hagia Sophia cathedral, which is located in Constantinople.
Creating a pendant template
If you've never built a pendant before, or seen one being installed when placing a dome on top of a building, you may want to create your own model first.
- Step one
A pendant has three shapes: a large sphere, a cube that fits into that sphere, and the cylinder that fits into the cube. Each needs to touch the other for this to work properly.
- Step two
When building the pendant, you will start by sculpting the volume of the sphere. You must remove the cylindrical volumes, of which there are three. These three include the two on the inside and sides and the one in the center. You must find the exact points of these three cylinders to determine the exact volume to subtract.
- Step three
You won't need the cube after finding the volumes above, so you can remove it from your model.
- Step four
The last step is to simply remove the bottom part of the new volume you found, as this will show you the final shape of what your pendant will and should look like.
New pendant shapes
Although pendants have been used for centuries, they are popping up in newer buildings everywhere. Many state capitol buildings use pendentives in their rotundas, especially those that offer huge panoramas for people to see.
Although pendants have taken over from squinches, it's probably only a matter of time before pendants are improved further or replaced with something new and altogether better. That's not to say pendants are going anywhere anytime soon, but with a little fine-tuning, they could look better than ever!
