Tres Unidos Footbridge Project
Newsletter Issue 2, May 2006
Currrent state of the project
Sag or camber?
Next steps
Our supporters
read our first newsletter
Current state of the project
Roughly a month has passed since we officially started the Tres Unidos project. Everybody who from time to time visits our projects homepage is witness to a step by step progress and the decisions we make which determine the bridges construction and design.
The easiest and therefore first decision we made was which kind of
timber we want to use. Among all the local available kinds of timber Quinilla was
by far the best. This tropical wood is hard and durable yet easy to work
with when freshly cut. Compared with other sorts locally used as construction
woods it is easily available and therefore very cheap. By now we even know that
it is to buy in Tres Unidos itself and no transportation costs will arise.Furthermore we defined design loads and figured out the general design
- Suspension bridge with pylons and ramps (64 meter free span)
- 4 load bearing cables with a bridge deck of 1 meter and a distance between hand rails of 1.4 meter (at the pylons)
- sag of 4 metres
- freeboard of 1.5 bis 2 metres
- maximum living load of 3 kN per square meter
- permanent weight of 1 kN per square meter
Static calculations made on this basis showed what weight is to be expected at any point of the bridge. This knowledge enables us to decide about the bridge’s crucial details like design of the pylons, look of the abutments or size of the foundation. For most up to date information about this please keep visiting the project’s homepage www.tresunidos.alpintechnik.de.
The biggest achievement on “social side” is our list of volunteers. Thanks to the help of Damaso Martinez we found the first 25 volunteers who want to take part on the bridge building. Their promises soon will be put to the test when they have to build the foundations on their own. (see “Next steps”)Sag or camber?
Part of our co-operation with "Bridges to Prosperity" is making a contribution to the compilation of a bridge building manual. In this context we had a discussion about how suitable a bridge design based on a sag can be for flat areas.
Whereas the American design team works on a solution for suspended bridges with a camber, we out of many reasons decided for the option with a sag. Our criterions:- We can use 4 instead of only 2 load bearing cables. This allows for smaller diameters which are much easier to transport.
- Both upper cables can be used as hand rails. An extra construction is not necessary.
- All hangers are of the same length; a strong advantage in production.
- Our pylons will have a height of four to five metres. Every additional meter makes transport and construction more complicated.
- We only need one abutment on each side which eases the construction process a lot.
Bridges with a camber of course are more stable and not so prone to wind, however in our point of view this does not countervail the disadvantages the erection of two abutments on each side, higher pylons or pre-stressed cables has. Moreover the building site in Tres Unidos is not so exposed to wind and strong wind loads have not to be expected.
The freeboard of 2 metres which we calculate with should be sufficient too and as "Bridges to Prosperity" founder Ken Frantz says: "A standard of five meters (freeboard) is great only for steep gorges where you have the entire Himalayas pouring into them."Next steps
From May 29th to June 6th our manager Eric Kuhn again
travels to Tres Unidos to finally start the bridge building. The main goal of
the trip is to explain the bridge’s design to the villagers of Tres Unidos and
brief the volunteers so that they will be able to build the foundations on both
sides of the river on their own.
Here in Germany we are currently organising a donations structure since we have been asked by many supporters how they can help us. As soon as we have any details we will publish it on our project’s homepage.
Our supporters
We were thrilled by the friendly response we experienced from almost everybody - clients, suppliers, friends and supporters of our company. Many of you offered their help and we already made use of some things:
- Karsten Fuge from
Statikbüro Lochas helped us with static calculations.
- Ney Linares
donated 1.000 Dollar for the bridge building in his village. We are going to
pay the first things out of this.
- Roland Weber from DSI Munich makes drawings that will be part of our construction manual.
- Outdoor specialist Globetrotter GmbH sponsored an IRIDIUM SIM card for our satellite telephone.
Many many thanks to all of you!
By the way, our homepage has a detailed list of costs and expenses which becomes regularly updated.Plautstraße 80, 04179 Leipzig
www.tresunidos.alpintechnik.de