Overpass Oasis: Bridging Nature With Innovation

Hello! My name is Andre. I am a student in Maine. I've worked on a variety of engineering projects using fusion 360. I have led in my school's robotics club, where we use CAD software and makerspace resources to solve real world problems. This year, we designed an automatic sprinkler system (based on a previous Instructables project) to help water the plants of our middle school gardening class.

Working in the robotics club introduced me to Instructables, and I took an interest to the monthly challenges. I felt the "Make it Bridge" challenge in particular was pertinent to the issues faced in my communities, and would be a good way to show my experience using BIM and CAD software.

My cable stayed bridge is the result of dozens of iterations; I first designed a small ten foot footbridge to cross a creek in the woods. I include the design of the foot bridge here, but my main submission is an arch bridge into a cable stayed bridge, as I preferred the design, and it allowed for more design freedom.

One of the primary goals in my cable design was to make it fully renewable and self sufficient. I also want to incorporate plants and bushes to create a more natural theme. By adding solar panels to the deck of the bridge, and creating gardens under the entrance and exit ramps, I feel like I've accomplished this goal.

Highlight of cable stayed bridge design:

Location: Located on Cochecho river, near the only public swimming pool in Dover, Great Bay Community Rowing Center and the Children's Museum in Dover, New Hampshire.

Who will use it: People living along either side (both area are quickly developing). Families moving into the town in the coming years can use the bridge to access the community facilities mentioned above.

How does it help: By cutting directly across two developing parts of the town, it reduces the walking distance pedestrians have to cover by 2500ft to 200ft. It also uses solar energy, and in most cases, will produce a surplus of energy to be fed back into the grid (calculations done at a later step).

Macbook Pro (Fusion 360, Blender)

Phone Camera

Sketch Book

Pencil

Ruler

My first idea for the location of a small bridge was a stream in the woods near my house. I had regularly crossed that stream as a child going hiking with my parents, and it was sometimes a struggle when the rocks were slippery. However, I ultimately decided that it could be easily remedied by a simple construction of wooden planks even though I already made a fully fleshed out design incorporating Generative Design with Fusion 360. So, I just include it in my submission to show my design process.

I wanted the bridge to be simple to assemble, strong, and semi modular, so I settled on making 3d printed side arches that held wood planks between them.

I started by drawing preliminary sketched on graph paper. I decided to use only five railings, with a curved top section, and wires running through below. For the final design, i removed the wires, and kept the top section, as I liked the more simplistic look it offered. My initial plans were to print the bottom section in concrete, but I decided to use metal instead, like on the DAR bridge. Concrete 3d printers usually have larger nozzle sizes and layer lines, leading to a lack of precision compared to metal deposition machines.

One of my main goals was to make the design modular and easy to construct. Each railing can be plasma cut out of a single sheet of steel, and only needs to be welded to a small plate to mount to the bridge assembly. The part slots into the 3d printed steel housing, allowing for a seamless fit. It's then possible to screw the railing into the bridge using the four holes in the steel plate. To protect the screws from rust, and to give the bridge a more streamlined shape, I designed a smooth cover to clip over each railing mount (visible in the rendered image).

Designing the side arches:

Creating the base model:

My plan for the supporting arches was to use generative design to create an organic supporting shape that could help the bridge keep its weight low and be feasible to manufacture. I started by creating a sketch, and drawing an arc that spanned around 30 feet. I then offset the arc, and closed the shape by connecting the offset line with the original arc. Exiting the sketch, I extruded the shape by a foot to create a 3d object. Now, I filleted most of the edges, and prepared to include the bridge deck.

Creating the wooden beams:

To create the deck of my bridge, I planned to use a row of two by fours inserted into the side arches. To do this, I created a single beam spanning five feet, and placed it at the edge of the side arch, perpendicular to the shape. I then used the pattern on path tool to create 45 beams in total. Since I wanted the beams to be locked into the 3d printed arch, I moved all of them into the shape, and used the combine tool to perform a boolean operation, cutting the shape of the beams away from the arch.

Using generative design:

I switched to the generative design space, and created a new Structural Component study. I selected the arch as the shape I wanted to keep (I didn't set the beams to obstacle geometry since my computer couldn't handle it, I just cut the shapes out of the finalized generative design). Since the average person weighs around 137 pounds (source), or 610 newtons, I added three forces to the arch pointing perpendicular to it's surface, as I expected a maximum of six people to be on the bridge at a certain point in time. Once the design finished computing, I mirrored the organic bridge supports, so that both the sides were assembled (see first photo).

Railing Designs:

Creating the base profile:

To create the hooked handrail design, I started by making two splines, each slightly offset from the other. I made the base of the double spline area fatter than the top, and ended the top spline in a sharp line pointing down. I created another line pointing from the bottom spline, so that the two lines would intersect. I then filleted all of the edges to create a more smooth and less aggressive profile. I exited the sketch, and extruded the body by one inch.

Creating the mounting point:

I wanted the handrails to easily slot into the bridge, so I created a cutout at the bottom of each handrail so they could fit into slots in the arch assembly. I also included a plate to be welded to the handrail that holds four 1/2" screws, to ensure the stability of the construction.

Designing the handrail

I made a sketch on the first, middle, and last railing, and created a sketch point in the center of the hook of each railing. I then used a 3d sketch to draw an arc passing through all three points. I used the sweep tool to thicken the sketch line to form a usable railing.

Rendering:

Materials:

In my final render, I assigned materials to each component to make the bridge more visually appealing. I set the side arches to stainless steel (as that is what's commonly used for 3d printed bridges), and also made the handrails in steel (for cost effectiveness and ease of manufacturing). The planks were made of alternating oak and cherry wood, and the screws and screw covers were made of stainless steel.

Render settings:

For my design render, I set the environment to the salt flats, and rendered using the cloud engine.

Why I Moved on from this Design

Manufacturing and cost:

Although 3d printing is an amazing technology, the limitations in size, cost, and material make it virtually impossible to create my design. Each side, weighing 864 kg, would cost upwards of $100,000 to print. Although the guardrails are modular, easy to manufacture, and cheap, the cost savings provided are heavily outweighed by the cost of the custom frame.

Benefit to the community:

Since the trail is barely used by hikers, and the stream isn't even an inconvenience for most people, my overbuilt and expensive design has more negatives than positives. The wood used is expensive to source and bad for the environment, while the nearly quarter of a million dollars that the project would require could be better spend on other things.

Location:

I decided to design this bridge for construction over the Cochecho River in Dover, New Hampshire. In the past years, I've rowed with the Great Bay Rowing club, and we go down this river nearly every day. Geographically, this is an excellent location, due to the developing areas above and below the river. By creating another bridge, people moving across both sides save almost half a mile.

Bridge Type:

Because the bridge would have to span over 200 feet, I decided to use cables to help with the weight of the deck. I first designed an arch style bridge, but then decided to make a cable-stayed bridge, with large abutments on both sides carrying the weight of pedestrians.

My initial design was inspired by the Margaret McDermott Pedestrian Bridge, where I constructed two huge arches, which supported the deck through two dozen cables. My second design also used cables, but it was more similar to the Sundial Bridge.

My goal for the second bridge was to design a large, mechanically sound, and good looking bridge. I started my plans by drawing possible designs on scrap paper. The first one was a dual arch design, but I quickly moved on to the second iteration. The deck is suspended by cables, which are mounted to the large concrete pillars at each bank to hold the weight of the deck.

Since these pillars were angled back, they are able to lift the bridge structure through their weight alone. Normally, there might be other cables pulling from the top of the pillars away from the bridge, but since the bridge experiences a relatively light load (pedestrians, not cars), the weight of the concrete is sufficient to counteract the cable tension.

With my cable supported bridge, I will be using much more detail in describing every step.

For each part of the design, I'll give an overview, talk about the CAD work, cover the actual construction, and assess the sustainability.

Overview:

The deck is over 200 feet long and suspended by the cables tied to the pillars at each bank. Yes, the deck needs to be robust, safe, and durable through well engineering. I settled upon using steel I beams to bridge the gap, while placing reinforcements periodically and plates above for walking. 

CAD Details:

Using the sketch menu, I created the profile of the I beams using the “Line” tool. I then exited the sketch menu, and extruded the shape using the “Extrude” tool to form the long 200 foot beam. Using the “Rectangular Pattern” feature, I made four copies of this beam in a horizontal line. 

To make the concrete side panels, I made a new sketch on the end of an edge I beam. I made a rectangle using the “Rectangle” sketch tool, and extruded the rectangle (minus the geometry of the I beam) a couple feet. 

To create the rest of these concrete side parts, I made a pattern along the length of the I beam, and mirrored them to the other side of the deck.

To make the deck panels, I used the sketch menu to create a large rectangle, and extruded it a quarter of an inch. I spaced these apart when duplicating to allow for thermal expansion (calculated below)

Actual Construction:

After looking at what other bridges of similar size used, I decided to use five W21 beams spanning 200 feet each to provide the main support. Along these beams, short supporting I beams (W16x100) would be welded to join the longer structural beams together. Since the supporting cross beams are a tiny bit smaller than the W21 beams, they fit perfectly between the flanges of the longer beams. Ideally, these would be welded, though it might be better to use sliding bolts to allow for more thermal expansion.

Thermal expansion is a large issue on bridges, especially where I live. Temperatures often drop to below 0F in the winter, and rise past 100F in the summer. Because of this large temperature range, bridges must be designed with thermal expansion in mind. As the temperature changes, the deck will flex, and the large aluminum plates that cover the deck will change in size. Because of this, each plate is offset 0.25 inches (calculated thermal expansion given the area of the plate) to ensure that there aren't any problems.

Sustainability 

To make this assembly as sustainable as possible, the high strength steel I beams can use recycled metal. This is extremely common in steel, as the material is 100% recyclable, and retains all its properties when reused.

Similarly, the aluminum used for the deck panels can be made of recycled material.

Overview:

My goal for the bridge pillars was to make them visually appealing and distinct as well as structurally solid, so I went with a sharp, tilted and angular look.

CAD Details:

To start making the pillars, I created a sketch of the basic profile. I wanted a more angular look, and hollowed out the interior to allow for easier pedestrian traffic. I then decided to tilt the whole structure backwards. This improved the look of the bridge, and more importantly, allowed the weight of the concrete and steel pillars to counteract the weight of the bridge (the cables would be attached to the top of the pillars, and pull inwards to the bridge).

As shown in the fourth picture, because of the weight of the bridge, there would normally be another cable put along the counter force arrow to counter the load of the bridge. In my bridge, this force is provided by the weight of the tilted back pillar.

Actual Construction:

This would be the hardest part of the bridge to construct in real life. The pillars stretch over 50 feet, and are intended to be made out of steel impregnated concrete.

These would likely be constructed at the work site, instead of being made at the factory, due to their immense weight and size. A method called slipforming would be used to form the concrete around the metal pylons. This method pours the concrete down onto a mold that is moving higher as the concrete solidifies. As the concrete sets, the platform containing a constantly changing mold moves up a step, and changes into the right shape for that segment. After a certain amount of steps, the structure is fully completed

If needed, the concrete will likely be post tensioned, which is when steel wires which were previously run through the mold are pulled together, compressing the whole structure, and leading to greater strength and reducing wear over time.

Sustainability:

During the slip forming process, many factors can be optimized for sustainability. Supplementary Cementitious Materials (SCMs) can greatly increase the sustainability of normal cement. These materials are mixed into unset cement, and provide added structural properties, while reducing the total concrete used. The most common SCM is fly ash, which is a by-product of energy generating stations using coal. Using this material in concrete reduces the amount of fly ash to go in the landfill. Another material that can be used is Slag Cement, a byproduct of iron blast furnaces. Slag cement can be used to replace 30%, 40%, and even half of the cement in a concrete mixture, greatly reducing the amount of actual cement needed.

Since cement production is one of the biggest contributors to greenhouse gasses, reducing the actual amount of cement used helps make production as sustainable as possible.

Overview:

Since the pillars are designed to sit on the ground (preferably a foundation), I needed to make them flat in respect to the ground plane. I made an offset plane from the bottom of the ramp, and cut the pillar body. This cut created two parts, the upper pillar, and the lower pillar. I removed the lower cut, making the upper pillar have a surface flush with the ground.

CAD Details:

The original pillar was a little too short to support over a dozen cables that were needed on each side to support the deck. I remedied this problem by extruding the rectangular flat top of the pillar up a couple meters.

I then needed to construct a walkway. I made a trapezoidal sketch wide enough to comfortably fit two rows of pedestrians, and extruded this sketch to join it to the original pillar (photo 3). After this step, I modified the material to match the granite/stone finish.

With the pillar design nearly finalized, I mirrored it across the deck. Since the top of the pillar is tilted at an angle, I would need to mirror the second pillar twice, one time across the middle of the deck lengthwise, and one time across the middle widthwise. To make these planes, I made a mid plane using both ends of the deck, and both sides of the deck.

Actual Construction:

Since these are modifications to the concrete pillars, these modifications would be accounted for in the mold of the previous step.

Sustainability:

See "Sustainability", step 11.

Overview:

Railings are vital to prevent people from falling off a bridge. OSHA regulations state that a railing must be at least 42 inches high for pedestrian traffic (source), so I made my railings 45 inches high. I began the guardrail design with the railing supports (flat thin parts that hold up the handrail). These parts are crucial for the structural rigidity of the railing and the aesthetics of the bridge.

CAD Details (Steps shown in third photo):

1. To make the profile of the railing supports, I first started a new sketch. In the sketch, I used the sketch "Line" tool five times to create the basic profile (a pentagon). I then used the "Sketch Dimension" tool to ensure that the railings were compliant with size standards.
2. Using the "Center Diameter Circle" tool, I created a circular profile at the top of the previous profile, serving as the resting point for the handrail.
3. Exiting the sketch menu, I used the "Extrude" tool to thicken the profile by 2 inches, making a solid body.
4. Since the bottom needs to rest on the concrete, I needed to cut away a square portion to make it fit. I positioned the railing support on top of a concrete side profile, and used the "Combine" tool to cut away the intersection volume. After that, the profile is complete (as shown in photo 2).

Actual Construction:

The railing supports a two dimensional profile, meaning they can be easily water-jet cut, plasma cut, or cast. The ideal material is probably aluminum or stainless steel. Aluminum does great with corrosion, especially when anodized or coated, while stainless steel is extremely low maintenance and can be cleaned easily.

Sustainability:

Since steel is the most recycled material on the planet, most stainless steel purchased for such a project would likely already be near fully recycled.

The recycling process in metals (in this case, steel and aluminum) helps reduce resource heavy mining and processing. Recycling stainless steel helps reduce the demand for iron, chromium, and nickel (three primary elements of the alloy), cutting emissions from the refining process.

Overview:

For the handrails, I decided to use a looped railing design, as I preferred the aesthetics over the normal single railing design. These were fairly simple to make, and I'm really happy with the outcome.

CAD Details (Steps shown in third photo):

1. I started a new 3d sketch, and used the "Include 3D Geometry" tool to include the rail support from earlier (this is to get the position of the center of the circle cut into the railing support). Using the center of the railing circle, I drew a line coming out of the railing support. I used the "Line" tool again to continue the path downwards, and made a final line moving back to the railing support. I then used the "Fillet" tool to smooth out the edges, resulting in a sideways "U" shape (see step 1, image 3).
2. Exiting the sketch menu, I used the "Sweep" tool to create a pipe segment following the "U" shape, creating the end of the railing.
3. To create the main portion of the railing, I used the "Extrude" tool to lengthen the ends of the "U" shape. I then mirrored the railing ends across the deck, completing the hand rail assembly.

Actual Construction:

The gold colored handrails would likely be made in dozens of pieces. The straight segments would be made by metal piping (brass, or painted aluminum), while the curved end segments would be custom bent tubing. This could be done by using a bending machine, or by welding different metal segments together.

Sustainability:

Aluminum would probably be the best choice for the handrails. Like stainless steel, it's almost always recycled, and it's softness combined with it's lightness make it easy to bend and handle.

Like the stainless steel rail supports, these aluminum handrails will be extremely easy to recycle at the end of the bridges life, while also being very durable and low maintenance during the operational lifetime of the bridge.

The railings could be bare polished aluminum, or they could be painted using eco-friendly paints (paints that minimize Volatile Organic Compound emissions). The aluminum could also be powder coated, a process that emits no VoCs, creating a durable "skin" over the metal that can last decades.

Overview:

To mount cables to the concrete pillars, there needed to be joints that are set into the concrete to attach to the cables. I first made a series of holes along the tops of the pillars to assign the mounting points. Then, I made a gold plate to mount all the individual wire clamps. Since every wire is angled slightly differently, I made each clamp mount to a joint, allowing for full rotational freedom. This means that as the bridge flexes with differences in temperature or wind, the joints can adjust to be in the optimal positions. If a custom part had to be made for each angled wire clamp, production would be much harder and much more tedious.

CAD Details:

1. I started this construction by making a sketch on the inner surface of one of the pillars. Starting a couple inches from the top, and inserting a couple more inches, I created the first circular object, with a diameter of 1.5 inches. Since there are twelve wires, I needed to make eleven more of these holes. To do this, I used the rectangular pattern tool, and selected the edge of the concrete pillar as the pattern direction. After stretching the pattern to a reasonable distance, I entered "11" to make eleven copies, and completed the command.
2. Now that I had twelve sketch circles positioned correctly, I extruded these to cut into the concrete support surface. This was to mark the locations into the pillar body, while also creating the anchor points for the wires. On top of the concrete, I decided to make a golden plate to complement the white of the pillar.
3. To make this shape, I added on to the previous sketch. I drew a rectangle around the previous twelve circles, and extruded this rectangle (but not the circles) out one inch. Now, I had a new body, which was a flat and thin rectangular prism that had twelve hole punches. To make the parts that wrapped around the pillar, I extruded the side of the rectangular prism near the edge by an inch, making a lip over the concrete pillar. I then cut the bottom face of the rectangular plate using the perpendicular edge of the concrete pillar.
4. Now that the bottom side of the gold plate contains two separate faces, you can extrude the far face to create an L profile. This thick L profile can now be modified to whatever aesthetics you want. In my case, I cut away most of the side profiles to make strips that stretch across the concrete.

Actual Construction:

To make the holes in the concrete, during the molding process, mounting points should be welded to the internal metal structure, and the mold should be adjusted to make room for the holes.

The metal decorative piece can be made a variety of ways, but the easiest is probably with plasma cutting then sheet metal forming. This makes mass production much easier, but the price of a mold would be expensive.

Sustainability:

See "Sustainability", step 15.

Overview:

These mounts were extremely complex to model and position, as each module contained two separate joints that needed to be positioned exactly to seat the cables.

CAD Details:

This assembly has three main parts (as seen in the above exploded view). The base/anchor, which sits in the concrete, the first stage joint, and the clamp.

1. I started with the anchor (right most part in the exploded view), which is a collection of three cylindrical bodies. I started with a sketch, added a circle, and extruded the circle to make the first flat cylinder. Then, using the face of the previous cylinder, I made another sketch of a thinner circle, and extruded that to the desired length. Finally, I made the last sketch on the thin cylinder, and drew a large circle to act as the end cap. I then extruded this circle to make the final design.
2. The next part I worked on was the first stage joint (top left part in the exploded view). This part contained two perpendicular holes to join to the other parts. I started by creating a donut shape (a cylinder with another cylinder cut out inside of it). Using the sketch menu, I created a circle, then created a smaller circle inside the first (matching the radius of the thin cylinder from the anchor), then extruded the whole sketch an inch. I then edited the face of this donut shaped cylinder with a sketch. Using the line tools, I made two vertical lines spaced one inch apart in the center of the sketch face. In the center of the sketch, I added another sketch circle, matching the radius of the end cap of the anchor. By extruding the resultant shape, I had two pillars perpendicular to the ring of the joint.
3. Since I needed to merge the top segments of the pillar to create the final shape, I made another sketch on the top of the two pillars. Since I couldn't make a sketch on two faces (even if they're coplanar), I needed to project the sketch to the other pillar. After doing this. I connected the pillars together using two lines along the edges. I then exited the sketch menu, and extruded this shape. After extruding, I needed to make another hole for the final stage of the cable mount to hook into. I made a final sketch on the side face of the previously extruded body, and cut out a hole. To improve the strength and looks, I finally chamfered most of the edges.
4. The last part (bottom part in the exploded view) was probably the most tricky to design. I started by creating a long cylinder that was larger than the wire radius. Using the sketch tools, I made a circle profile on the face of this cylinder with the same radius as the wire, and extruded this profile (as a cut) into the original shape. Using the sketch tool again on the modified edge, I made two rectangles close together to act as the clamping surface. I extruded this shape a couple inches into the body, and cut away the space in between. Now that there was a clamping surface, I made a sketch on the outer sides of these surfaces to create holes for screws. Using the circle tool, I made two 0.5” circles, and extruded these as a cut into the plates. I found screws and nuts on a CAD model library, and imported and aligned them into the final assembly. 

With all the parts created, I used the align tool to match the different elements of the assembly. I first use the align tool to move the anchor onto the gold plate from the previous step. I then used the align tool to move the bottom pivot joint onto the anchor by selecting the top edge of the bottom plate, and the bottom edge of the anchor end cap. Finally, I used the align tool to position the clamping part to the pivot joint.

Actual Construction:

These parts would likely be welded sheets of steel, or CNC milled. They would likely have to be custom made, as the total number of parts (24) doesn’t necessitate mass manufacturing.

Sustainability:

Since steel is necessary given the small size of the mounts, the joints would again be made out of recycled stainless steel.

Overview:

For the deck cable mounts, I decided to not use a hinge, and to instead just have a metal clamp welded to the rail supports. Since they are located at the deck they will be much easier to maintain and change out, which doesn't necessitate a complex pivoting joint. Like the assembly on the pillars, this clamps with two 0.5" bolts around the steel cable.

CAD Details:

1. I started the design by creating a sketch, and adding a circle object. I then offset this circle using the offset edge tool to make a ring. To make the clamping mechanism, there needed to be flanges coming out of the ring. To design this, I made two rectangles slightly offset from the center. I then used the trim tool to cut away the non needed edges (steps shown in third and fourth photos).
2. By extruding this profile, I was able to make the clamping assembly. Since the flanges don't extend along the full length of the object, after a couple inches, I made a new sketch on the extruded profile. This sketch was just a ring, and I extruded it the remaining distance. Since the shape was still a hollow cylinder, I made another sketch on the end, and extruded it to cap off the remaining shape.

Actual Construction:

This part would be made of a stainless steel pipe with flanges welded onto it. The middle would be cut away to allow movement of the clamp, and the whole assembly would be welded to the handrail supports.

Sustainability:

See "Sustainability", step 17.

Overview:

The wires were fairly easy to design. After constructing the clamps, I used the 3D sketch tool to draw profiles, then thickened them to make volumetric cables. I initially wanted to model the actual strands (using a rotation in the sweep tool), but my computer couldn't handle the computations required for this operation, and crashed every time I tried to make the geometry. I opted instead to use a material when rendering, as it was almost impossible to tell the difference.

CAD Details:

1. I started a new 3D sketch, and included the geometry of all the clamps previously designed. I then added sketch points in the holders (pictured in photo 2 and 3) to mark line end points. I then repeated this pattern for all twelve of the pillar clamps, and all twelve of the deck clamps. Now, using the "Line" tool, I created a line going from the highest pillar clamp to the farthest deck clamp. I worked my way down the pillar, making a line from each pillar sketch point to the corresponding deck sketch point.
2. Now that all the lines were drawn out, I needed to thicken them to create a volumetric object. Using the "Sweep" tool, and selecting the inside circular edge of a clamp, I made a cylinder cable for each sketch line.

Actual Construction:

Usually, the cables would be pre made, and bought on the spool. If the company making this bridge wanted to make their custom cable, they would need to spool thousands of strands of steel (usually high strength steel) to make a single threaded cable.

Once the cables are ready, they would be attached loosely to the anchor points, and then tensioned, a process requiring a machine called a dynamometer to measure the tension in the cable. The cable is stretched out, then the anchors are secured to the cable again to maintain the cable tension during the bridge's operation lifetime.

Sustainability:

Like most of the other components on this bridge, these steel cables will use recycled steel materials. To further reduce emissions, it might be a good idea to source the high strength steel locally, which reduces traveling distance.

You could also choose suppliers that use electric arc furnaces (EAF) instead of traditional blast furnaces. These EAFs use significantly less power because of their increased efficiency, and as a result, will cause less emissions.

Overview:

Lights are important for any pedestrian structure to allow for easy navigation at night. For my design, I opted to create two main sets of lights. On each pillar there are two light panels, each of which has 19 separate flat lights. To illuminate the walkway, each railing holder has a tiny LED light built in, allowing for the deck to be visible even during the night. These lights were fairly easy to model and position, as they were very simple geometrically, and were mostly identical. Additionally, each tower has one bright beacon light on the top to alert aircraft.

My goal was to make the lights subtle, but also have them complement the design. I feel that having both the large floodlights and the smaller deck lights provide a good contrast in style, and help focus the viewers attention more on the architecture and design of the bridge.

CAD Details:

1. I started the large flat pillar lights by creating a sketch on the pillar face. Using the "Rectangle" tool, I created a small shape in the sketch, and I used the "Chamfer" tool to chamfer all the edges a little. I then used the "Rectangular Pattern" tool to create 18 more duplicates of the rectangular shape, resulting in 19 rectangles. Now, using the "Center Rectangle" tool, I selected the middle rectangle (the 10th one from the top) and made a new larger rectangle to border the whole group of smaller rectangles.
2. Exiting the sketch menu, I first extruded the whole shape (just a rectangle). Then, to create the lights on top of the rectangle, I changed the visibility of the sketch to show the drawing, and extruded the 19 smaller light bulbs out of the original rectangle.
3. For the deck lights, I started my sketch on the inside face of one of the railing holders. I created a small rectangle using the "Rectangle" tool, and extruded it out of the railing by 0.5". I then made another sketch on the newly created rectangular prism to create a smaller offset rectangle. I extruded the second rectangular sketch by 0.25" to make the light. For both the floodlights and the deck lights, I later refined the design by chamfering various edges to help the aesthetics.
4. The top beacons were extremely easy to model. Since the tips of the pillars are flat, I started a new sketch on them, and created a slot using the "Center-to-center Slot" tool. I then extruded this narrow shape a couple inches, and fileted all the edges.

Actual Construction:

The lights would likely be outsourced by the company building the bridge. Wiring would be done by holes designed into the concrete (pipes put in during the molding process).

Sustainability:

Because of the solar deck, all the lights are powered by clean, renewable energy. The lights are going to be LEDs due to their efficiency and availability.

By using the people sensors, the bridge will be able to analyze the trends in usage. When pedestrian usage is heavily reduced, the lights can be dimmed to reduce light pollution, and when usage is heavy, the lights can be fully utilized.

Overview:

Sensors are an integral part of any bridge. They can be used to monitor the health of the bridge and to monitor the environmental changes around the bridge. The temperature sensor in my design contains two separate thermistors (temperature probes). One is embedded into the concrete directly, and one sits above the concrete to detect the ambient temperature.

CAD Details (Steps shown in third picture):

1. I started by making the profile of the main box. Using the sketch features, I made a small rectangle following the dimensions of a generic temperature sensor I found online. I chamfered each corner of this rectangle, and then added the holes. To make the screw holes, I used the circle tool to make a circle with diameter 0.25" centered in the rectangle. I then used the sketch constraint tool to constrain the distance of the circle to the edge. In this case, I set the distance to 7mm. I then copied this circle, and used the sketch constraints tool to move it to the bottom of the rectangle
2. I extruded the whole sketch to create a solid body using the "Extrude" tool
3. On top of the previous body, I made a new sketch, and drew a rectangle using the "Rectangle" sketch tool that had corners on the chamfers of the previous shape. I then used the "Offset" tool to offset the edge inwards to create a wall. I exited the sketch, and extruded the resultant shape.
4. With this new shape, I needed to close off the enclosure (it currently has an open top). I created another sketch on top of the open lid of the previous shape, and extruded the flat surface inwards to create a lid. I then used the "Fillet" tool to curve the edges of the lid, the top of the lid, and the sides of the flanges.
5. To make the temperature probe wire, I started with a sketch on the top face of the box. Using the "line" tool, I created an "L" shape, and using the "Fillet" tool, I smoothed the edges. Since I needed the wire to come out the middle of the box, I moved the whole sketch down a couple inches.
6. Using the "Sweep" tool, I thickened the previous line. On the ending surface of that wire, I made a new sketch, and drew a circle using the "Circle" tool that was slightly larger than the diameter of the wire. I then used the "Extrude" tool to thicken this shape to make the thicker end of the thermistor probe. To make the antenna, I made a series of differently sized cylinders using the "Cylinder" tool, and joined these together.

Actual Construction:

Sensors are almost always outsourced when building a bridge. In this case, these temperature sensors are fairly cheap and easy to find from a variety of manufacturers.

Sustainability:

The thermometer can greatly help with maintenance. Since all materials change in volume in response to temperature changes, this sensor can help predict when parts require maintenance or are fully worn out.

Over the lifetime of the bridge, the temperature sensor can also be used to assess how concrete reacts over time when used in such a bridge. This collected information allows better decisions in future buildings or bridges.

Overview:

A vibrating wire sensor is a device used to measure strain in metal, concrete, or other structural components of a bridge. Usually, a steel wire is used, and the frequency at which this wire vibrates is an indication of the stresses in the material. Since the ends are attached to the material, tiny changes in the material (allowing the ends to move microscopically) will affect the resonance of the wire.

These sensors are extremely important, as they can signal problems in a design, and help make sure that a bridge is operating as expected.

CAD Details (Steps shown in third picture)

• Since both sides of this sensor are symmetrical, I started by making half of the object. Going into sketch mode, I used the "Center Diameter Circle" tool to create a small circle.
• I then used the "Extrude" tool to thicken the circle into a cylinder, and chamfered one of the edges using the "Chamfer" tool.
• I started another sketch on the recently chamfered side, and created a smaller circle on that face. I then extruded this smaller circle to form a long rod, which was joined to the original shape
• On the outer edge of this rod, I started a new sketch, and made a slightly larger circle. I extruded this larger circle to create a thicker cylinder. I then repeated this same process to create another even thicker cylinder at the end of the shape. On the far edge of this final cylinder, I created a new sketch, and using the "Line" tool, I made a box aligned with the circle of the edge.
• I extruded the previous sketch to form a mounting point.
• Using the "Hole" tool, I made a thin hole through the whole assembly.
• Since I now only had half of the body completed, I needed to mirror the shape. Using the "Mirror" command, I mirrored the body across the base of the larger cylinder (marked with a yellow construction plane)

Actual Construction:

Like the temperature sensor, the vibrating wire sensor would be purchased from a separate supplier, and later bolted into the steel. Although there are only three in the CAD model, an actual bridge might have many more in different locations (in the concrete, other steel components, on the railings, etc.).

Sustainability:

The vibrating wire sensor could be used to verify the material expansion predictions of the temperature sensor, and help predict when to optimally conduct maintenance.

Overview:

A person sensor, which is basically an infrared laser that scans movement, is useful to track bridge traffic. This information can be used in assessing the effectiveness of the bridge, to figure out what seasons the bridge experiences the most use, and to plan out future urban developments.

In my design, there are two people sensors in total; one is located on each end of the bridge, facing inwards towards pedestrian traffic. Since the sensors are mostly just boxes with a small laser, they were extremely easy to model.

CAD Details (Steps shown in third picture)

1. I started the design by creating a rectangle in the sketch menu using the "Rectangle" tool.
2. I then used the "Extrude" tool to thicken the profile. This part is the base of the sensor, where it mounts to a surface.
3. On the flat face of the previous object, I created a new sketch. Using the "Offset" tool, I made a larger rectangle around the border.
4. I then thickened this new rectangle using the "Extrude" tool, and smoothed all the edges using the "Fillet" tool.
5. I started a new sketch on the face of the previous body, and used the "Center Rectangle" tool to create a small surface where the sensors would sit. Inside this rectangle, I used the "Center-Diameter" circle tool to create two small circles (representing the IR sensors). I extruded the sketch into the previous body, and modified the materials to match real life sensors.

Actual Construction:

This sensor would be purchased and installed after construction on this bridge.

Sustainability:

By tracking bridge usage and monitoring traffic, a person sensor can be used to schedule maintenance more efficiently, helping to conserve resources needed for maintenance and reducing unnecessary check-ups.

Overview:

All of the previously mentioned lights and sensors need a way to be powered. Since I hoped to make the bridge as sustainable as possible, I created a modification for the deck, which covered the walking surface with a giant array of solar panels. These could be used to generate energy during the day, charging up a small battery, and releasing the energy at night to power the lights. 

On average, solar panels are 20% efficient (meaning they convert 20% of the oncoming solar energy into electricity). This means that on average, each panel produces 200 watts per square meter. Since the deck is 2.2 meters wide, and 63 meters long, the total surface area covered in solar panels is 138.6 square meters. This means that on an extremely sunny day, these panels could generate 27720 watts of power, or 27 kilowatts. 

Since most of the sensors on the bridge are battery powered (generic example: https://www.multitech.com/models/RB90000218LF ), we shouldn’t need to account for them. Even if they were wired to a central battery powered by solar panels, the power draw would likely be negligible compared to the lights. Assuming the tiny lights in the bridge each draw 5 watts (https://www.amazon.com/Flashlights-2000Lumens-Rechargeable-Waterproof-Collapsible/dp/B0B5P15ZQY/ref=sr_1_21_sspa ), the total draw from all 48 lights would be 240 watts. 

The floodlights would draw considerably more power. Assuming that one floodlight uses 400 watts (https://www.hpwinner.com/uploads/file/hpw-spec-flood-light-fl2c-series.pdf ), the total watt usage for all four in my design would be 1600 watts, or 1.6 kilowatts. 

Adding the total energy draw together gives us 1840 watts during use. 

In New Hampshire in the winter and fall, nights are very long, lasting for around 14 hours on average. In the summer and spring there are around 10 hours of darkness in a day. 

Now, starting with the winter and fall months, there are around 10 hours of light during a day. Assuming that two thirds of these hours are cloudy/rain/snow gives us around 3.5 hours of usable light. Since the solar panels can generate 27 kilowatts of power under full sunlight, we get 94.5 kilowatt hours of energy for the energy produced. 

From our earlier calculations, we know that the electronics all need 1840 watts during use. If the darkness lasts 14 hours, that means the electronics need 25760 watt hours, or 25.8 kilowatt hours. 

Since there is more energy generated than consumed, we can conclude that the solar panels are sufficient to power the lights in the winter. 

In the summer and spring, there are around 14 hours of light every day. Assuming that around one third of the daytime is cloudy, there are around 9.5 hours of usable light every day. 

Using the same methods demonstrated above, we can calculate that the panels would produce around 263.3 kilowatt hours every day. Since the nights only last 10 hours, the lights would only need 18.4 kilowatt hours, meaning that there would be a large excess of power. 

Through these calculations, it’s clear that by using the deck solar panels, my bridge could be fully self-sufficient. In perfect conditions, the bridge generates much more power than it needs, and this excess power could be fed back into the town through the grid. 

It’s important to note that my calculations are extremely rudimentary. They don’t consider the angle of the panels, temperature changes in efficiency, and many other variables. Still, the calculations give a basic idea of how well the solar panels will perform, and help to demonstrate that the bridge can be self-sustaining.

CAD Details:

1. I used the sketch tool to cut a series of extremely shallow rectangles into the deck surface. I colored the top surface grey, and the bottom surface blue to reflect the color of solar panels.
2. In blender, I just used a solar panel material on a flat surface to display the design

Actual Construction:

There are a variety of bridge deck walkable solar panels available online (example), so finding a source shouldn't be too hard. After installing the aluminum deck of the bridge, the solar panels would bolt on top, and provide a walkable surface.

Overview:

The green walkway is a crucial part of the bridge design. Plants grow under the ramp, and come out through the grates on either side. The plants help me make my bridge as sustainable as possible, which is one of my main goals for this project. The greenery contrasts with the industrial theme of the pillars, and helps the whole structure fit in more with the rural New Hampshire feel. 

I decided to go with a ramp as it was the most accessible option to everyone. The ADA (Americans with Disabilities Act) states that any ramp must have a grade no more than a 1:12 ratio. This means that to drop one foot, a ramp must be at least twelve feet long. Note that in this case, length means horizontal distance, NOT the length of the surface. 

CAD Details (Steps shown in fourth picture):

1. I started by making a sketch on the pillar, where I drew a very thin rectangle using the “Rectangle” tool. Since the back of the pillar is curved, by extruding this rectangle using the “Extrude” tool, the ramp gets a slight tilt. At the end of this extrusion, I made a new sketch on the side of the ramp, and drew a straight line upwards. I then excited the sketch menu, and using this straight line I cut the previous body using the “Extrude” tool. This made the edge of the ramp perpendicular to the ground, and allowed me to start a curve. 
2. Using the flat surface created in the previous step, I once again used the sketch menu to create a curved ramp. I made two circles using the “Center-Diameter Circle” tool, and cut them off using the “Line” tool, creating a quarter turn. I then excited the sketch menu to extrude the object and join it with the ramp.
3. Next, I completed the ramp by extruding the last face all the way until it hit the ground. Before doing this step, I verified that the incline was less than a 1:12 grade. 
4. I decided that the curved ramp didn’t fit the rest of the bridge's design, so I edited the original sketch in the timeline to create a sharper shape. I also used the “Appearance” tool to change the material from the default steel to marble. 
5. Since the ramp can't support itself on such a thin surface, I needed to construct a foundation underneath. I began by starting a sketch on the ground plane (using the base of one of the pillars). I then used the “Project” tool to create the profile of the ramp on the ground plane. Exiting the sketch menu, I used the “Extrude” tool to extrude the created sketch to the faces on the underside of the ramp. 
6. To create a grate effect, I needed to first hollow out the bottom shape. I used the same sketch as before, and used the “Offset” tool to create thin walls close to the edge. I extruded these shapes to cut into the previous solid shape, making an air gap between the outer wall and the inner wall. Using a free Fusion 360 Voronoi tool extension, I created a sketch on all the outer edges of the ramp. I then extruded every voronoi object into the outer shell to create the organic grate design. I then colored the inside wall gold to create a nicer background color. 
7. During the voronoi creation process, some cells were missed, so I edited the original sketch to draw in every missed cell. Since I had only created one ramp, I used the “Mirror” object twice to create another ramp on the other side.

Actual Construction:

The top of the ramp would most likely be built out of sheets of steel welded together. The bottom supports would also be metal, including the grates, but there would be a substantial amount of soil at the bottom to support plant life. This soil would likely also help the stability of the ramp while also providing space for the plants to grow. 

The garden would need to be planted in a couple different stages. You should start by removing any large rocks, and verifying that there aren’t any utility pipes close to the surface of the ground. 

Since the garden area is a long strip mostly in the shade, plants will need to be able to grow out of the grates to reach the sun. It would be a good idea to plant some ground cover plants, and also some fast growing taller plants that can stretch through the grill. In this example, I’ll use Japanese Spurge (short plants to form a mat), and English Ivy (tall plants to reach the grill). 

Then, you need to pick out the correct type of soil. For decorative plants, loam soil (a mixture of sand, silt, and clay) is perfect. A pH (acidity) level of 6.0 to 7.0 would be perfect for these plants. In case the pH of the soil is unknown, it would be useful to bring pH testing kits and pH adjusters in case the acidity is undesirable. 

Before placing the soil, it’s important to get rid of any weeds or pests in the garden location. Then, it’s good to loosen the current soil (to mix it) using either a garden fork or a rototiller. You should aim to loosen the soil to a depth of around 8 to 12 inches. 

Next, you should place a thin layer (2-3 inches) of compost over the old soil. This helps to add nutrients to the soil, and encourages faster plant growth. On top of the compost, layer around 12 inches of topsoil, and mix everything (topsoil, compost, old soil) using a spade or a garden fork. 

After mixing the soil there needs to be a level surface for plant growth. Using a rake, try to make a flat surface, while also breaking up any large clumps of soil. 

Next, you need to transplant the plants from the pot into the garden. Starting with the Japanese Spurge, a transplant would be most effective during the early spring, as that is right before the plants experience major growth. In the garden, cut out holes spaced 6-12 inches apart the same size as the transplanted plants. Since Japanese Spurge can quickly widen to totally cover the ground, it’s ok to space them fairly far apart. The holes only need to be a couple inches deep, as this plant’s roots are very shallow. After inserting the transplants, put a small ring of mulch around each plant, making sure not to cover the actual plant. 

For the Ivy, you should dig holes a couple inches deep spaced around 18-24 inches apart, allowing sufficient room for growth. Add a layer of mulch around the plants (a similar process to the Japanese Spurge), and ensure that they receive plenty of water for a couple months. 

Both plants need to be watered and taken care of for a couple months after the transplant, to ensure that they can successfully grow and adapt to their new environment. Both plants should be fine after that period of time relying on just natural rainfall. The Japanese Spurge should form a thick carpet underneath the ramp, while the Ivy should spread up and through the grates to reach the top of the ramp. 

Sustainability:

The plants grown under the bridge help to offset the emissions produced in the manufacturing process. They can also purify the air near the town.

After finishing the design in CAD, I still needed to render the bridge to make it presentable. I decided to use Blender, as it was a software that I had used in the past, and because there were many tutorials available online. 

I wanted to import the design into Blender as separate components, allowing for easier texture mapping and assigning of materials. Since Blender doesn’t support 3MF uploading, I had to use an open source Github extension (https://github.com/Ghostkeeper/Blender3mfFormat ) to properly create my bridge. 

I then used the “BlenderKit” library to quickly assign materials to various objects. Since I wanted to create an environment to display the bridge, I needed to make a river. I used a terrain tool to make a small river bed, and created a plane to act as the water. After adding these materials, I then used a particle system (set to “hair”) to create grass on the river, and created a vertex group to prevent the grass from spreading into the water. 

Since the design in Fusion 360 of the ramp didn’t include any foliage, I used a free plant library to add a couple dozen unique plants under the ramp. 

I tinkered with all the camera settings to render, and finally was happy with the result.

Congratulations! You've reached the end of this Instructable. Thank you to Autodesk for running this competition, and good luck to everyone else!