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Mock up Process II.

Mock Process I.

HALS (Historic American Land Survey )

HALS is a committee who checks the design of any new structure that will be built in historic lands. Since Payne Lake is a historic land, we also had to consider that aspect of our design, which is why we researched old bridges on Alabama. 

Once the concept was completed and we had an over all design, series of renderings were sent to our client. From now on, the details may change, but the over all look is going to stay the same. These Images show the view of the bridge at different locations around the lake. Every image has a little map of the lake next to it that shows where the person is viewing the bridge from…

Our client, Cynthia Ragland, is going to submit these images to the committee along with a research that Gene Ford. Gene is an Archeologist who works for Moundville Archeological Park. Hopefully Gene’s documents and his point of view is acceptable to the committee.  

No more Pontoons…

How to Connect the Pontoons to Bridge?

How to Connect the Pontoons to Bridge?

What is a Comfortable Angle?

Now there is a section for the bridge, but there are different ways to experience this section. What is an appropriate angle for the walls? 

We tried to create the space with a couple of pieces of Foam Boards. We marked the walls at different angles, and asked student in studio to walk through the section, and tell us how they feel about each angle.

70-70

  • The roof had to be so high since the walls were tilted outward 
  • Almost too big, so handrails would be necessary to hold on to them, since the walls were away from pedestrians
  • Felt unstable since the walls were tilted toward outside

75-80

  • The difference in angles made people feel disoriented 
  • The space felt unsafe, uncomfortable
  • It looked like a mistake

80-80

  • There was plenty of room even for two people to walk side by side, yet narrow enough to feel safe walking on the water while protected by lattice truss
  • The roof didn’t have to be as high as 70-70

80-85

  • The difference in angles made people feel disoriented 
  • The space felt unsafe, uncomfortable
  • It looked like a mistake

85-85

  • too narrow
  • felt crunched by the structure, since it was too close to you

Over all the angle: 80-80 seemed to be the solution. We could have a 3 feet wide walkway, and yet spatially be comfortable at waste height, and the bridge didn’t feel like a narrow tunnel. 

Fresh Eyes! Module C. Decking is directly supported by trusses Low center of gravity Triangulation happens without the three sides of trusses touching  The structure is close to the water Decking is acting as roof and protects the structure from rain least amount of material Easy sonstruction Dan wheeler/Architect is one of our critics who came from Chicago. After we presented to him he made a suggestion that made everything clear!  By moving the figure from the top of the decking inside the section, we suddenly had a section that functioned: The trusses were protected by roof One could experience the full length of truss Triangulation happens in the section The walkway can be as narrow as 3 feet; therefore, Live load is decreased to its minimum. Since the walls are tilted outward the walkway is wider at waste height, so 2 people can walk comfortably side by side Low center of gravity Forestry has provided a document called ” FSTAG” which stands for Forest Service Trail Accessibility Guidelines. In that document they require Live Load of 65-85 lb. /PSF. We have been trying to decrease our live load because the bridge will, almost, never be fully loaded, and that means pontoons would float so high on the surface of the water. Aesthetically we did not like that idea…  The current critique would allow us to have a section that had the most narrow walkway, and decreased our Live Load to 1/3 of what it was before!  

Fresh Eyes!

Module C.

  • Decking is directly supported by trusses
  • Low center of gravity
  • Triangulation happens without the three sides of trusses touching 
  • The structure is close to the water
  • Decking is acting as roof and protects the structure from rain
  • least amount of material
  • Easy sonstruction

Dan wheeler/Architect is one of our critics who came from Chicago. After we presented to him he made a suggestion that made everything clear! 

By moving the figure from the top of the decking inside the section, we suddenly had a section that functioned:

  • The trusses were protected by roof
  • One could experience the full length of truss
  • Triangulation happens in the section
  • The walkway can be as narrow as 3 feet; therefore, Live load is decreased to its minimum. Since the walls are tilted outward the walkway is wider at waste height, so 2 people can walk comfortably side by side
  • Low center of gravity

Forestry has provided a document called ” FSTAG” which stands for Forest Service Trail Accessibility Guidelines. In that document they require Live Load of 65-85 lb. /PSF. We have been trying to decrease our live load because the bridge will, almost, never be fully loaded, and that means pontoons would float so high on the surface of the water. Aesthetically we did not like that idea…  The current critique would allow us to have a section that had the most narrow walkway, and decreased our Live Load to 1/3 of what it was before!  

Module A. Spatially makes more sense No extra roof structure  Higher center of gravity Columns are not around wood Excellent view toward outside If used transparent material for roofing, so one can look at the structure of the roof Minimum cladding material Triangular section A lot of up lift load Not much wind load since the structure is transparent Module B. Awkward/wasted space Lower center of gravity Heavy structure Needs to be covered all the way since the truss continues to the bottom Horrible view: The orientation of triangle would cause the pedestrian to see roundwood webbings instead of water, since they would be looking downward.  Most stable due to the form of the structure/triangle Two people can not walk side by side, unless the structure is very wide Triangular connections are not safe No up lift or wind load Module D. Close to water Truss is not being used for optimum strength A lot of material Requires additional cladding Already triangulated Easy connection to lilly pads Load is supported by tension Module E. Close to water Provides enclosure/ juxtaposition to lilly pads A lot of wood Tricky triangulation Needs to be covered  Keeping with vernacular Load is supported in tension Evenly distributed center of gravity Difficult construction Module F. Load is hanging from compression member Low center of gravity Triangular section Protecting structure from water below decking Close to lilly pad Maximum tension vs. compression Roof needs work Module G. Almost no roofing View toward outside from all sides Protect the walls from water Over structural and safe Least amount of metal Module H. Using a transparent cladding to protect the wood against humidity Different bottom joints connection to stop the walls from rocking Heavier roof since wood is used vs. other cladding material Module I. Reduction of metal/Round wood is most of the structure Roof has come down to protect the truss Extra structure to support the roof Lower center of gravity due to the weight of the structure More than one person can walk side by side Better view Very heavy structure Structural redundancy/ Safe Module J. No head clearance/spatially awkward/wasted space A lot of extra rood metal Never two people can walk side by side Higher center of gravity Normal view toward out side Requires a counter balance under water Lattice truss is not feasible with current dimensions Least amount of material is used It relies heavily on both connections on corners Connections of the triangle are not safe Up lift load Open view

Module A.

  • Spatially makes more sense
  • No extra roof structure 
  • Higher center of gravity
  • Columns are not around wood
  • Excellent view toward outside
  • If used transparent material for roofing, so one can look at the structure of the roof
  • Minimum cladding material
  • Triangular section
  • A lot of up lift load
  • Not much wind load since the structure is transparent

Module B.

  • Awkward/wasted space
  • Lower center of gravity
  • Heavy structure
  • Needs to be covered all the way since the truss continues to the bottom
  • Horrible view: The orientation of triangle would cause the pedestrian to see roundwood webbings instead of water, since they would be looking downward. 
  • Most stable due to the form of the structure/triangle
  • Two people can not walk side by side, unless the structure is very wide
  • Triangular connections are not safe
  • No up lift or wind load

Module D.

  • Close to water
  • Truss is not being used for optimum strength
  • A lot of material
  • Requires additional cladding
  • Already triangulated
  • Easy connection to lilly pads
  • Load is supported by tension

Module E.

  • Close to water
  • Provides enclosure/ juxtaposition to lilly pads
  • A lot of wood
  • Tricky triangulation
  • Needs to be covered 
  • Keeping with vernacular
  • Load is supported in tension
  • Evenly distributed center of gravity
  • Difficult construction

Module F.

  • Load is hanging from compression member
  • Low center of gravity
  • Triangular section
  • Protecting structure from water below decking
  • Close to lilly pad
  • Maximum tension vs. compression
  • Roof needs work

Module G.

  • Almost no roofing
  • View toward outside from all sides
  • Protect the walls from water
  • Over structural and safe
  • Least amount of metal

Module H.

  • Using a transparent cladding to protect the wood against humidity
  • Different bottom joints connection to stop the walls from rocking
  • Heavier roof since wood is used vs. other cladding material

Module I.

  • Reduction of metal/Round wood is most of the structure
  • Roof has come down to protect the truss
  • Extra structure to support the roof
  • Lower center of gravity due to the weight of the structure
  • More than one person can walk side by side
  • Better view
  • Very heavy structure
  • Structural redundancy/ Safe

Module J.

  • No head clearance/spatially awkward/wasted space
  • A lot of extra rood metal
  • Never two people can walk side by side
  • Higher center of gravity
  • Normal view toward out side
  • Requires a counter balance under water
  • Lattice truss is not feasible with current dimensions
  • Least amount of material is used
  • It relies heavily on both connections on corners
  • Connections of the triangle are not safe
  • Up lift load
  • Open view


Lattice Truss View

More Things to Consider

  • Do we built the bridge with temporary platform, build the lattice truss there, and then lift them up?  Philosophically if there was a platform to build the structure over it, that means there is a connection that allows a person to go across the water. Why should one build a bridge to construct a bridge over it? 
  • Do we have vehicular access to site? No
  • Do we have access to electricity? No
  • Do we have enough room to build close to the site? No

If we can not build at the site or close to the site, the pieces have to be pre-fabricated. Since the site has no vehicular access, may be they should be floated out there. If we have to float the pre-fabricated pieces out there, should we have a floating bridge? 

By floating the bridge, the structure’s foundation is not touching this historical land. It is a very thoughtful way of touching the ground. So…

  • How much do we know about buoyancy?
  • What do we use as our pontoons? 
  • How much do they cost?
  • How durable they are?

A lot of farms that survived Clarck-McNary act, eventually turned into catfish farms. Payne Lake used to be a farm which is now a manmade lake with fishing opportunities. It was an intriguing concept to use use catfish farmer’s pontoons for our bridge. We needed to contact some local businesses and find out about them. It was not difficult to find the guy who manufactures them since we are in ”catfish capital of Alabama”.

Pontoons normally last about 20 years, and not too pricy. How many do we need? It depends on “Live Load” and “Dead Load” of the bridge. We need to know the section of the bridge, and how much load creates a safe balance?