My Pedestrian Bridge Model

Welcome everyone, to my first Instructable! My name is Patrick Lian, and I'm in New York City from the high school of Staten Island Technical. I am currently 15 years old and just finished my sophomore year.

The bridge I will be showcasing was made in Inventor, an Autodesk software. It is a pedestrian bridge, meant to connect two areas of land together, bring people together, and strengthen social infrastructure and civic life.

Above, I have some images of my bridge in different views, some close up and one far view to demonstrate the size of this bridge.

Underneath, I provided the main assembly file of my bridge for anyone curious or interested. In addition, I will be providing all the part files including a presentation and documentation of my bridge.

I used the online software of Inventor to create my bridge. The reason I chose this software is because of my prior experience with this software and its ability to create different types of files which would benefit me as it gives me tons of options to work with. For this particular project, I decided to use multiple part files and in the end assemble them together in an assembly file.

Locating a site for my bridge was harder than expected. My previous attempts at this were flawed due to the environment, distance, and the abundance of bridges nearby, making my bridge mostly useless. I then connected back to my personal life, reminiscing the struggles of crossing the Verrazano-Narrows Bridge or the Staten Island Bridge due to traffic. The area I chose has both a good environment and a good cause to lessen the traffic on the Verrazano-Narrows Bridge as it's the only way to get to Staten Island from the other boroughs. My goal for this bridge is to get more ways to connect Staten Island with Brooklyn as well as have an aesthetic design to go with it as well.

Sketching the bridge model would help visualize what I will try be creating and notice any flaws within what I'm designing. Deciding on using both a suspension and an arch bridge, I went for a design that was a spiral inspired by the Huaihai South Road Canal Bridge located in China. I wanted my bridge to contain the same spiral design but elevate it to the next level by adding more than one spiral.

This was also a convenient time to measure some dimensions. I used google maps to measure the distance between Seagate and South Beach, which was approximately 3.35 miles. For the height and width dimensions, I researched the average for both dimensions but changed them accordingly throughout my project to fit the bridge's proportions.

There were going to be 4 part files I would need to create: the body, the spirals, the suspensions, and the railings.

The first part file I would need to create is the body of the bridge, to have a base to put everything else on.

I started out creating the body of my bridge, using the dimensions mentioned previously. I started by converting all the dimensions to inches as that is what Inventor's unit is in. 225915.939 inches was the final length of this bridge after some adjustments mentioned in the next paragraph. The width is substantially smaller than the length coming in at 3090 inches. I then decide to run the command extrusion on my base, which would ultimately make the base 3D, with you providing a height.

After an extrusion of 906.6875 inches, I built the arch beams that would support it as every bridge needed support underneath. I created a plane using the lengthier side of the bridge base and created a sketch of it. The idea was to build 1 side of the arch beams and mirror it, saving me time. I created the arch beams using an ellipse or an oval and cut them in half, resulting in the arch shape. I then had to copy and paste the arches using the copy command. This was where I had to do some adjusting of the length as the arches were not corresponding with the ends. Another extrusion later, I was one step closer to finishing my body. Lastly, it was time to mirror the planes using the another plane in the middle of those two.

The spirals were the main design for my bridge. This was surprisingly the easiest part out of all. I figured out I could use the coil command as the design is very similar to the spirals I was looking for on my bridge. After 1-2 YouTube videos, I figure out how to use coil. I had one problem with the coil, and it was that the coil command made an entire loop around and my bridge doesn’t require the entire circle loop. I figure out how to solve that problem by using the dimensions of my bridge base and extruding cutting a gap between the spirals so my bridge base can fit perfectly in between. 

The third part file required was the suspensions, and this was arguably the hardest part of the project.

I had to make planes at an angle so that they would fit between the base of the bridge and the spirals as to the support. It got easier after a while due to me just creating one suspension and using the rectangular pattern command for the rest saving me some time. Each suspension took very long due to them being at different angles and it ultimately was the most annoying and time consuming part of this project. In the end, I settled for 7 suspensions per spiral, 4 towards the inside, and 3 towards the outside.

The last part file I made was the railings, and this was made for safety reasons and to keep everything in line.

The railing was made using the sweep command first to make the cylinder shaped bar. I then used the rectangular pattern to duplicate the bar to make a railing. I then extrude another cylinder on either side for an ending to the railing.

To assemble the part files I had to first place them all together in one file and constrain them. There were different kinds of constraints, but the ones I used were mate and flush. These constraints required a face from each file so it could be constrained.

I started with placing my body, which was the main base of the bridge and where most of my part files were going to be constrained. Some files didn't have a flat face however, and I had to improvise by making a small rectangular prism and using those faces to constrain the file onto the body.

I constrained the spirals first onto the bridge body, then the suspensions, and lastly the railing. Each constraint took an offset value, which was a value the constraint would be offset based on the constraint you put.

I made a presentation file, which showcased the movement in which the bridge would move when disassembled. The documentation file was made off of the presentation file as the presentation file included an exploded snapshot of the bridge, which was the view used in the documentation file.

Underneath, I provided both an mp4 video of the presentation file as it would not upload onto Instructables and the documentation file.

I really enjoyed the project as a whole and went through it during my ups and downs. I was thinking of giving up sometimes (especially during that suspension section) but remembered that I went this far already, and to complete it and showcase it to the world.

I hope you enjoyed my first instructable and this certainly isn’t my last.