Architect's Statement
CONTEXT: BRIDGE OF DUALITIES
The 35th Street Bridge is a physical and metaphorical expression that addresses the transition between the urban condition and nature. How the bridge manifests itself in addressing this context is at the core of our investigation. It becomes an opportunity to be more than a mere passage over the transportation thoroughfares. We are interested in making this bridge an experience, directly and indirectly reflecting its context as well as its beginning/end points of departure. The potential for the bridge becoming iconic in its presence for this southern portion of Chicago becomes our aspiration within this strategy.

ISSUES: [INFRA]STRUCTURE
The uniqueness of having the existing infrastructure, Lake Shore Drive and the Metra tracks, is our next consideration for the generation of the form of the bridge. With the western portion over the tracks having more vertical supports, it begins to act as a natural anchor or counterbalance to the eastern half over the Drive. These, in concert with the review of structural limitations that need to be thoughtfully addressed, begin our development of the concept, or “big idea”.

ISSUES: ACCESSIBILITY
Another issue of importance is how to creatively respond to accessibility guidelines. We view this as a critical design problem. All should have equal opportunity to enjoy the experience of the passage. It is our self-imposed design parameter to do as much of the ramping at 1:20 slope to limit the amount of slope transitions across the length of the bridge and simplify the construction. This also gives the bridge an elegant silhouette from the distant views along Lake Shore Drive.

ISSUES: MATERIAL SELECTION
It is our goal to select materials that have durability, ease of maintainability, and visual impact. We will consider materials that are readily available and easily replaceable. Some consideration to products with recycled content is also to be investigated.

ISSUES: ENVIRONMENTAL SENSITIVITY
We believe every project has a requirement to be sensitive to the environment that exists. It could mean saving trees, limiting products that are not of a recyclable nature or of natural materials, or other more general requirements to maximize sustainable practices. Our bridge design takes these ideas as a requisite design parameter, and applies this information to the initial concepts.

APPROACH: DUALITIES
In an attempt to reconcile the two contexts that the bridge is sited within, we start with the idea of an organic form that bifurcates as one moves from urban to nature. The bridge begins as one path that follows the grid of the city, extending over the Metra tracks. As one moves along the path, it angles to be perpendicular with the tracks and Lake Shore Drive with an armature that continues the city grid as it moves toward the Drive. As the path widens at this transition point, the path diverges into two separate bridges, one a narrower path for ambulatory pedestrians, and the other wider for cyclists, strollers, and wheelchair bound individuals, aiding in limiting the congestion that can sometimes occur along these bridges.
As the bridge splits, the levels shift, giving both bridges views focused back to the Chicago skyline. The pedestrian level is lowered to give an intimate scale to the path. The cycle path is higher to enable people to see over and have an unobstructed view as well back to the city. These changes also aid in reinforcing the idea of the transition of the differing contexts. By breaking down the bridge into the parts, the strategy of the bridge “growing” out of the city is reinforced, giving the appearance of the bridge as a “flower” that has a stem and petals, reaching for the park and lake.

Other features of the bridge, include a shelter area so people are able get out of the elements during inclement weather and lighting that utilizes photovoltaic cells to power and light the bridge.

APPROACH: [INFRA]STRUCTURE
The bridge’s structural system is a directly influenced by the existing infrastructure in place. We conceived the bridge in three parts: the western path over the Metra tracks, the paths over Lake Shore drive, and the path into the park. Starting with the western portion, we utilize the existing points of the vertical structure to support the bridge, giving it a stable base for which to support the Lake Shore Drive paths. An armature then extends out from this portion of the bridge over the Drive with an asymmetrical cable system supporting the bridges mid-portion. This structural expression reinforces the original strategies and gives the bridge a three-dimensionality from the distant views. The third component is conceived as an extension of the landscape. A third of the path is to have a “grass-crete” product to give the illusion of the park climbing up the path, and to limit the expanse of concrete by providing and area of respite for individuals using the bridge. The directions of the bridge paths are in response to some of the existing configuration of the streets and trails.

APPROACH: ACCESSIBILITY
All pathways of the bridge have a maximum slope of 1:20 or “flat”. This is done to minimize landings along the path to create a simplified construction of the bridge(s). The pedestrian path is 10’-0” wide and the bike path is 20’ wide. Where the two paths combine, they slowly merge into the required 25’-0” wide pathway. At the east end of the pedestrian way we have located a stair to get down to grade. This was done to initially to get down to grade for the pedestrian and to provide some separation of the circulation paths at the park level.

APPROACH: MATERIAL SELECTION
The materials were chosen with the above criteria in mind. Concrete is used as a structural element for the horizontal surfaces as well as the expressive architectural gesture of the armature that cantilevers over Lake Shore Drive. The base of the pedestrian path is to be a recycled wood decking material. This is to distinguish between the functions of the bridge and to provide a different scale.
Railings are a combination of materials to give visual interest along the bridge from one side to the other. A combination of terra-cotta and lexan is utilized to give a visual impact along the edges. A differing precast concrete is used on other rails as a counterpoint to the horizontal concrete surfaces. The shelter at the intersection of the paths consists of corten steel, provided homage to the industrial character of the trains below.

APPROACH: ENVIRONMENTAL SENSITIVITY
Lighting is one of the biggest concerns we have regarding energy usage for the bridge. We have conceived the light to be self-sustaining, using no energy from the city. The unit includes a photovoltaic panel to power the light and a photocell to turn it on and off. Other environmental issues revolve around material usage addressed earlier.

CONCLUSION
With all this considered, the resulting design is one that can become a landmark for the neighborhoods that surround it. The design is one of timelessness and elegance, a marker for all to see from great distances. The 35th Street Bridge is the path that lends credence to the “City on the Lake” and extends that into the urban landscape.

Evaluation Committee comments:
I like the idea of the solar technology and the simple cleanliness of the structure and site plan...and the large terraces and sculptural quality.
Good resolution...good connection to land. Elegant.
Nice form architecturally.

Architect's Statement
Context : a transition at the edge condition
The North Avenue Pedestrian Bridge is an important link between the expansive parks and green space of Lincoln Park and the activity of the pathway and North Avenue Beach. This relationship places the bridge in a critical position in the procession from city to park to beach. It also ties together the places separated by Lake Shore Drive, creating a gateway to the city for those approaching downtown on Lake Shore Drive and a lasting image as one moves north away from the bridge.
At this edge condition, where land meets water, there are very strong natural forces at work. The Lake Michigan shoreline was originally composed of low dunes and grasses. Wind and water constantly rework surfaces and forms, creating a landscape in constant flux. It is here that the great expanse of the lake presents itself. Its waters, too, are constantly changing, from placid to tumultuous, from clear to frozen.

Issues : the blending of forces
In designing the bridge, the primary challenge is to provide an accessible, safe crossing of Lake Shore Drive for a wide-range of users. As it exists now, the bridge is not readily accessible to all persons, and, on the lakeside, makes for an extremely congested intersection of bridge and path. The entire bridge would slope at 1:20, reaching its apex just off the center of Lake Shore Drive.
On the west side of Lincoln Park, the ramp gradually rises from the ground and arcs in plan across Lake Shore Drive, landing parallel to the pathway. The gentle curve of the plan eliminates any sharp or awkward turns, providing a smooth transition from one side to the other.

The broad base, located in the area between the merging of the pathway and bridge ramp is composed of low terraces, benches and an overhead trellis. The terraces serve as a gathering area at this critical intersection, providing ample space to relieve congestion. Before crossing to the Lincoln Park side, bikers and pedestrians can stop and relax before continuing on their journey. For those coming from Lincoln Park and the city, this area allows users to re-orient themselves, to pause before moving on. All of these activities take place removed from the busy pathway.

As a larger vision, the bridge needs to transcend these pragmatic considerations and seamlessly meld together all of the forces acting upon it at this edge condition, responding to several scales. As seen from afar, it should be an inspiring sculptural element that enhances its environment and surroundings. Also experienced more intimately, the bridge should provide a tactile, sensual experience as one moves toward the lake.

In order to achieve this fluidity of movement and form, the bridge rests within the site as an outgrowth of the park and beach, not as an object set on the landscape. As a transitional element, the bridge allows the park to continue across it. In this sense, the bridge does not merely serve as a connector between two disjointed pieces, but as continuation of one as it meets the other. Along the outer rim of the bridge, a zone of grass provides a place to pause on the bridge as well as reinforces the desire to extend the park across Lake Shore Drive.

Environmental Sensitivity : a self-sustaining ‘sail’
While the overall image of the bridge is imagined as highly sculptural, providing an alluring entry to the city and a sensual experience to walk along, it also plays an important role in educating the public on the possibility of harnessing, and living harmoniously with, nature. The path of the bridge and its canopy are shaped to track the movement of the sun as it rises over Lake Michigan and sets below the western skyline of the city. The trellis, comprised of a series of louvers and photovoltaic panels, creates a self-sustaining ‘sail’ that provides energy for the bridge.

During the day, the photovoltaic panels would bathe in the sun, absorbing energy and storing it in batteries housed in the eastern splayed base of bridge. At night, this energy would be converted to light, turning the bridge into an inviting beacon that lures pedestrians to the lake. From Lake Shore drive, people would be greeted with arcing slits of light that announce their entry to the city.
The prominent location of the bridge perched over Lake Shore Drive would put such ‘green’ technologies on display to a large audience, and could serve as a showpiece for new technologies. Just as the bridge serves a gateway, or beacon, announcing arrival to a physical destination, it also announces an arrival to a new way of thinking about the environment.

Materials : the fluidity of concrete
The fluid gesture of arcing across Lake Shore Drive would be realized with concrete. The monolithic nature of concrete mimics the homogony of the sand dunes. The span across Lake Shore Drive would be executed with pre-cast concrete sections. Where the bridge meets the ground on the lakeside, cast-in-place concrete would allow for the sculptural shaping of the base. The ability to cast textures into concrete would be exploited, especially in the terracing on the lakeside of the bridge. Adding textures and patterns to concrete where it comes in contact with the sand would provide a smooth transition from the beach to the bridge and provide scale to the surfaces that engage people.

The more articulated and airy trellis attached to the concrete structure alludes to grasses that grow from within the sand. It would be composed of thin, reflective metal louvers that tie in with both grasses and the sun reflecting off the water. The orientation of the louvers would provide alternating patterns of sunlight on the surface of the bridge pathway below.

Railing on the outer edge, or south side of the bridge would be a continuation of the precast concrete section. Its profile would be an extension of the trellis above. The railing on the inner rim would be as translucent and thin as possible, maintaining the thin profile of the inner edge.

Vision : the landscape extended
The design of a new bridge for North Avenue provides an opportunity for Chicago to add to an exciting portfolio of architecture and structures. Because it is physically removed from a pre-existing built context, the bridge can exist as a sculptural object, or in this case, extension, of the landscape. Its location and function allow it to be a bold, inspiring vision, not only in form, but in its approach to the environment as well.