making a suspension bridge-- from grass

For more than two years we've been talking about this bridge, the Q'eswachaka over the Apurímac River in Peru. It's the last suspension bridge remaining from the time of the Inka, and has been maintained by the four communities along the river for more than 500 years. It's iconic, it's spectacular, and it's an engineering marvel.

Why? Because it's made of grass.

Chronicles from the Spanish note that there were more than 200 such bridges in the Inka Empire, mostly in the region known as Chinchaysuyu. The same chronicles note that the Spanish were terrified of these drooping swaying bridges, and fell to their knees before them. However some were so large that armies moved across them. They may be grass but they are remarkably safe and sturdy.

We'd been consulting with the world-expert on this bridge, a civil engineering professor at MIT. We wanted to make the bridge the case study for engineering solutions of the Inka for the Chinchaysuyu region (How do you safely cross high mountains and river gorges with the materials around you?). We wanted to build a bridge across our big atrium space. Bold!

But not to be in the end. Most were supportive, and the engineering was not the problem. Visitors were. Special events and programs would be challenged by it. In the end, we couldn't. So we started to explore how to get a bridge segment into the gallery. And we got lucky.

Peru signed the agreement to do the Folklife Festival last June, and one of the twelve case studies they would present would be the Q'eswachaka. Done! Now all we had to do was convince the communities to cut the bridge into two parts for the museum.... Yes, they had a good laugh at that.

So here's the story of the bridge, in three parts, including building the bridge, installing the bridge, and then preparing the bridge for the museum. Well, four parts, as I'll eventually finish up with the installation in the museum, still a few weeks away. I'm still awed that this happened on the National Mall and will now be part of the museum. Amazing! This is a great example of why I love my job.

 The technical crew for Folklife designed and built these "bridge abutments" of two shipping containers with a steel custom-built frame on top. Over-engineered by default, because of location and public and safety rules, it was impressive to watch them construct it. They used a forklift to mount the steel frame on the container, but had to get a crane to mount the one container on the other.

 And when done, the graphics were applied. Yes, from one side you could see the Washington Monument, and if you stood on the other, the U.S. Capitol.

And suddenly they were here! Fourteen members, representing the four villages, including the bridge master (the subject of all our media in the gallery about the bridge) and the chief engineer. 

 Two ladies were among the group. Traditionally they do the weaving. The grasses are pounded, then twisted into cords. The above photos show both grass and cord.

 The men do the cable work. If you are not part of the community, you should not cross the cables when they are stretched out. If you are female, you cannot. There are numerous cultural protocols at work here, and we needed to learn them quickly. And I'm proud to have been the one to discover that, and help get a barrier erected! 

 This bridge was 2/3 the length of the real bridge, so they used 20 cords to make each rope, instead of the normal 30. They are twisted together, pulled, and stretched, to provide tension and staying power.

 Three ropes are then braided to form a floor cable.

Then it's the equivalent of a tug-of-war to stretch the cables.

The cables are heavy! 

 But very flexible. Piles of them were just all stacked up together.

 Two ropes are twisted to form the handrails.

 These too would be stretched and pulled.

Four braided cables make the base and two twisted cables make the handrails. The sides are simply cord. They spent the first few days getting this part ready, in order to install the cables on Sunday, before their "weekend" break.