This is the final installment of my project for our Fabric.A.Tion studio. For my amphitheater I choose to design a project that would work with the land and be integrated into the landscape, hence half of the building being built into the earth. I also wanted the amphitheater to visually demonstrate some sculptural values as it is located in a sculpture park. One of the last main things I wanted to incorporate was adaptability and usefulness. Knowing the theatre would only be used a handful of days out of the year, yet be present 365 days of a year, the theatre has a green roof which can be used at any time, and the seating is meant to be as unobtrusive as possible yet still provide function. Architectural mesh would be used across the facade of the building holding the dressing rooms, and would visually represent the rhythmic qualities and variance of the music and performances on the stage.
I really enjoyed our studio trip for the fall ’10 semester. We went to UC, Pitt, Washington DC, and Cambridge Mass, all in 4 days. The car trip was a little tiring but overall the trip was a great experience. Many things over the course of the trip interested me, but there were a few that stood out the most. One of the things that really fascinated me was in Pittsburgh, I was just amazed by the amount of fans the Steelers had, and their general support, for a team that (I think) really isn’t that great, but hey thats just my 2 cents! But truly one of the things that really interested me was the versatility of steel mesh. After seeing all these examples through the trip, I was left wondering what methods could be devised to really push the limits of what this product can do, and how it can be engineered to be so much more. Another thing that I enjoyed during the trip was seeing all of Cambridge’s working models of the mesh. I feel that this could really help the consumer better understand and apply their product, and I feel this could have been a valuable asset if we (the students) could have seen this before we began processing our ideas. But, I really enjoyed the tour of the factory. I just love seeing how things work, and the tour really left me satisfied with understanding the mesh, because I got to travel through the manufacturing process and see what changes were made, and how.
I started doing my work on designing a fully functional footbridge that would be using several elements of tension, including steel mesh working with the structure. I wanted to focus on elegant components, and visual simplicity. I came up with the scheme of a floating pedestrian bridge held up by 2 legs swung out and against each other.
This is an elevation of the bridge.
The mesh in tension would be the Rope pattern, and would actually be load bearing. The use still conforms to the current production standards.
This is a quick drawing of how I imagine the connection between the rope mesh and the steel stabilizing cable should be. Hopefully it will fully support the mesh, as well as successfully transfer the forces from the mesh to the rope.
Here is a top render to help you understand what is really going on.
Here is a rendering of a close up of the bridge. As of now, the connections that are holding the bridge to the ropes are currently being researched and designed further, and are currently placeholders.
This is a picture of a method I plan on using as a connection between the steel cables, and the steel elements that hold up the actual footbridge.
So I decided to further narrow down my research to fit the topic of tensile structures; which includes Suspension and Rope Bridges.
Basic Structure and Physics
The image above depicts all the components of a suspension bridge that are either in compression or tension. The diagram shows the physics of why suspension bridges stay standing. The cables and suspenders that are in tension are integral in sustaining the decks camber, and transfer the weight and load of the deck to the towers. The towers then take the weight that are passed on to it from the cables and deck and direct that force into the ground and keep the bridge raised. The anchorages and cables on the outsides of the towers play important roles as well. When the towers are loaded with the weight from the cables and deck in the center, they naturally want to fall inward. The outer cables and anchorages help to counteract that force and keep the towers under pure compression, as well as carry the load of the short segments of deck on the outside of the towers. Due to the nature of suspension bridge elements being in either pure compression or tension, these elements can be very slender, creating elegant forms.
This diagram helps depict details of the force diagram, specifically the forces acting on
the anchor block, and the connection of the cables to the tower.
Suspension Rope Bridges
Many modern rope bridges today operate with similar physics to that of suspension bridges, and borrow many of the suspension bridges’ components, such as; the Weight Bearing Tower, Anchoring Cables, and Anchoring Points. Using these elements allows the rope bridge to be lighter, stronger, and easier to assemble. Below are a few pictures demonstrating the qualities as mentioned above.
Some interesting suspension bridges to consider:
Suspension Bridge Materials
Suspension Bridges can use a wide range of materials for a variety of purposes. Some of the earlier suspension bridges didn’t actually use steel cables in the tension components, but actually used steel beams pancaked together and strung between towers such as the Clifton Suspension Bridge above. The more modern practice used today is steel cables woven together with hundreds of steel fibers to create a single cable. This method keeps it’s strength even if a few of the fibers within the cable are flawed. Whereas with the earlier beam method, one bad beam could bring down the entire bridge.
Cable Stayed Bridges
Cable stayed bridges share a certain similarity between suspension bridges, but they are drastically different. The main structure of suspension bridges as mentioned above are primarily the anchor blocks and towers. Whereas cable stayed bridges rely entirely on the towers and have no need for anchoring blocks. Cable stayed bridges can range from one tower to support the entire bridge, to multiple towers in line to support a continuous deck.
Cable stayed bridges enable the designer to have quite a bit more leeway in deciding how a bridge is laid out. Using a cable stayed bridge platform allows for the bridge to curve, due to the focal point where all the cables attach. Cable stayed bridges also allow the designer to take liberties to redefine the space of the bridge through the varied use and location of cables. Below are a few examples demonstrating some of the available methods of using cable stayed bridges.
Hybrids that combine suspension and cable stayed bridge elements are interesting compositions that take multiple traits of either category and combine a variety of unique bridges. One such bridge is the Brooklyn Bridge.
Above is a link to my full sized presentation poster from the Sep 8th presentation.
Topic: Bridges – Specifically: Suspension/ Progression (Timeline)/ Inca Rope Bridges
Info: I’ve begun to look into:
- Inca Rope Bridges: How they work, their history, surviving examples
- Bridge History: Timeline of bridge history, types and uses
- Suspension Bridges: How they work, famous examples, different methods/ problems, past/present/future limits
Response: I’m just fascinated by the huge variety of existing bridges and the different ways they are engineered and constructed. I’m also amazed at the extent of progress that has happened in the past several decades. Simple bridges were used as early as 2000BC, but only in the past 150 years have the bridges that we know today, come in to existence. And over those 150 years, bridge design has excelled tremendously, as we push the boundaries on length, weight limit, height, and spans.