Connecting LA's Communities: a New Pedestrian Bridge Designed to Encourage Inclusivity

Hi! My name is Lachlan McDermott, I am a rising Senior at Geffen Academy at UCLA, Los Angeles, and I'm currently 17 years old. The work that follows shows my designs for a new pedestrian bridge for the Los Angeles River. I have been an avid enthusiast of the Autodesk CAD/BIM suite of tools since I was young; I found this project to suit my talents quite well.

In a large city like Los Angeles despite having many multifaceted cultures and groups often we find ourselves divided and split despite this diversity. This bridge aims to help start solving this problem by connecting Downtown Los Angeles (DTLA) with the largely Hispanic population that currently lies adjacent but is currently stranded. This bridge aims to not only be a physical bridge but act as an inspiration and motivation to others to help make more change in their communities.

Supplies needed:

1. A Fusion 360 Software License
2. Paper and pens for drafting and preliminary designs
3. Access to google maps

The problem this bridge is solving is twofold: social division and lack of physical connectivity. Despite the multicultural and diverse nature of Los Angeles, there exists a noticeable division between different cultural groups and communities. This division often results in a sense of isolation and disconnection among the residents, resulting in disputes and a general lack of cohesion. Additionally, the largely Hispanic population living adjacent to Downtown Los Angeles (DTLA) is currently cut off from the city due to the lack of proper physical infrastructure. This bridge would solve this.

Other issues with current bridges are that they lack proper pedestrian access, aren't in the correct locations, have massive costs (in excess of 10 million dollars), lack safe bicycle and simultaneous walking access, and have heat islanding effects with massive steel and metal usage. I aim to solve all these problems with my bridge.

Finally, my bridge design aims to be a symbol of unity, connecting diverse communities and fostering positive change in LA. By addressing social division and lack of connectivity, I aim to inspire a more inclusive LA. With the hope to create a better, more connected city.

I started by going to google maps and using the map scale to determine the total span that my bridge would need to have. Between Google Maps and Google searches, I was able to determine that the bridge would need to span 200 feet and the main deck would need to be 25 feet above the base of the river to avoid the highest water heights seen during floods; this height should provide sufficient vertical clearance to allow for potential flooding or debris flow in the LA River. Depending on the area's flood history, a clearance of at least 15 to 20 feet above the normal water level is advisable. (Normal water level is around 1-5 feet) From these first measurements, I was able to determine all other requirements and measurements.

Bridge Measurements:

1. Bridge Span: 200 feet (as provided)
2. Bridge Height: 30 feet (as provided)

Main Bridge Body:

1. The main body of the bridge should be wide enough to accommodate both pedestrians and cyclists comfortably. A minimum width of 10 to 12 feet is best. This allows three people to walk side by side and also provides enough space for a cyclist to pass safely.
2. 14 feet will be used in the design

Guard Rails

1. Height: The guard rails should be able to prevent pedestrians and bikers from having accidents and possibly falling off the bridge; at the lowest point a height of 42 inches is standard practice, a higher height (52 inches) might become more practical in locations where viewing isn't critical.
2. Slots between guard rails must NOT allow for children or small animals to easily fit between.
3. Design: The design of the guard rails should complement the surroundings and the bridge design, they should seem very thematic and natural; there should be a large emphasis placed on aesthetic elements that blend well with the bridge's architecture.

Ramps and Approaches:

1. It is imperative to have entry and exit ramps on both sides of the bridge to ensure smooth access for pedestrians and cyclists, these ramps should have a gentle slope with railing to help accommodate people of all varying abilities and ages.
2. The approaches leading to the ramps should be wide enough to allow a smooth transition for pedestrians and cyclists at the same time without fear of collision; all the way from the ground level to the bridge deck.
3. A width of 15 feet will be used.

Surface and Materials:

1. Main Surface: The bridge deck should have a smooth surface to provide a comfortable experience for pedestrians and cyclists. Concrete is an ideal choice as modern concrete can be embedded with Co2 to reduce the carbon footprint of the bridge while remaining a strong and durable choice.
2. It is imperative this concrete is painted with white enamel to prevent extreme heating in the punishing LA sun; this will also make usage of this bridge more comfortable for pedestrians.

Lighting:

1. Proper lighting should be installed along the bridge to enhance safety during nighttime use. Bright low energy LED lighting fixtures will be used as they provide excellent visibility to pedestrians. This will also make the bridge much safer at dawn and dusk.

I love to use paper and a pen when I am brainstorming ideas. Many other mediums can be used, but I personally love the old-fashioned style of drafting.

I began my design by sketching the empty LA river conduit, starting with the inverted trapezoid-looking shape; I started to sketch lines across the bridge slowly drawing and adding columns, ramps, people, benches, lights, and all of the aspects I needed based on my requirements. After multiple iterations, some up close specific drawings of benches, lights, ramps, seating areas, and futuristic specialized benches I settled on a preliminary design that could be made in Fusion 360. (As seen above in the sketches)

I began my CAD modeling in Fusion 360 by opening a new project and first designing the LA River canal that my bridge would span across. I began with a couple of sketches which when push pulled created the main canal. I then marked out the general space in which my bridge would reside. This allowed me to determine the dimensions of the ramps that would be needed, I could determine the ramp grade, wall size, thickness and height, and general spacing in relation to the rest of my bridge.

The custom ramps for my bridge I found were the hardest part to model. I wanted a ramp that started out flat and as the incline increased the railings and sides would seem to form out of the flat part. This proved much harder than I thought. I tried to use sketches and many push-pull cut routines to no avail. I found Fusion's "Loft" tool to be incredibly helpful. I was able to create my flat cross-section at the start of my ramp and with a spline that I used as my midline (seen in the image) I was able to connect the starting cross-section to the ending cross-section. This was a super effective and fast way to make my bridge ramp that has walls that seemed to form out of nothing. I added a turn at the top of the ramp once again utilizing one of Fusion's many tools "Sweep". It allowed me to quickly create the 90-degree bend with all of the complex geometry from my path that would lead to the main deck of my bridge. I added bevels and chamfers at the base and top of my ramp to finish it off. Then duplicated the ramps, turned them 180 degrees, and placed them opposite of each other on opposite river beds. This left me prepared to make the supporting piers for my bridge.

Next, I moved my focus toward creating the pillars that my bridge was going to stand on. Due to the design of the LA River, a 1-foot deep 5-foot wide trench sits in the middle of the river which contains the primary water flow most of the year. Meaning that any 3 or 5-pillar combination was out of the image as I couldn't have a pillar obstructing that smaller water flow, as it would increase evaporation too much. I opted for a 4-pilar design as the gaps with a 2-pillar design were too large; in excess of 100 feet. I once again used my favorite "Loft" tool and created a first face, with an oval, on the floor of the river and lofted it to a square that would mate with the bottom of the bridge deck. After chamfering and beveling the edges all 4 pillars were finished.

I wanted to create seating areas where pedestrians would feel invited to sit and relax and be able to view a gorgeous skyline all, while not blocking other pedestrians walking or biking. I had this idea while at the beach when I noticed a series of benches directly next to the bike path which caused obstacles for both those biking and walking. I also aimed to make sitting on these benches as comfortable as possible, often metal benches exposed to direct sun become extremely hot so I devised a plan to create shade while retaining the gorgeous view and keeping the seated pedestrians out of the pathway. I solved this with an alcove that formed up from the railing on the bridge. The railing wrapped around an outcrop in the path which offset the benches from the main path. This alcove that wrapped around created a little haven of shade for those sitting on it. By staggering the placement of these alcoves I would allow each bench to have a full unobstructed view of the city skyline behind it. This design aims to make the best of all worlds, encouraging the people of LA to treat this bridge as a viewing attraction and activity not just a method of transportation.

The last piece that would complete my design was a good outdoor bench design that matched well with the same overall look of my bridge; a simple metal bench wasn't good enough and a super modern hyper curvy chair wouldn't match my design style. I took inspiration from the same style that I had used on the bottom half of the main deck on my bridge. I decided to randomly place metal and wood beams in what, to the casual observer, might seem totally haphazard and random but actually leads to multiple seating spots. It holds the same sharp 90-degree corners, wood and metal combination while retaining functionality and beauty. I think these benches will help finally tie together the interaction between the pedestrians and the bridge, allowing them to not only experience the bridge but utilize its function in a very immediate way.

With all of the components individually planned, designed, and created; all that is left is one large integration into a final finished bridge! The ramps, main deck, benches, railing, lights, and figures were all added together to create one cohesive bridge.

This is a link to view and download your copy of my bridge! Feel free to add and change whatever your heart desires:

https://autode.sk/43BjdvS

In conclusion, I had a great time planning, designing, and iterating on this bridge. I gained a lot of valuable experience in creating functional and aesthetically pleasing models, an area where I previously had room to grow; I had never designed or looked into bridge design before this competition. This competition also allowed me to hone my skills in CAD design and planning. I look forward to participating in more competitions in the future.