Annex 5

The history of Chicago is intimately tied to the development and character of the Chicago River. From the first moveable bridge at Dearborn and the River, to the latest redevelopment of Wacker Drive, the Chicago River has provided a conduit for commerce as well as a social gathering space. Today the River acts as a strong physical presence, shaping buildings and plazas along its edge as well as the connection of the City to the ever-developing Lakefront.

The idea of contributing to the Lakefront development with an improved Bike Path consisting of a dedicated Pedestrian Bridge is a major civic design opportunity. Our proposal locates the new bridge as far to the east as possible to highlight the bridge and path as a place separate and apart from the Lake Shore Drive vehicle bridge. The approaches to the footbridge are proposed as bermed ramps with sloped slides, essentially designed as landscaped extensions of the park on either side of the River. The elevated bermed ramps will serve as overlooks to the Lake providing a new viewing vantage point for pedestrians and cyclists.

In addition, our proposal seeks to establish an Urban Marker at the mouth of the River. Visible from both the Lake and the City, the bridge will mark the location of one of the major urban features of the City of Chicago.

DESIGN INTENTION:
As well as an Urban Marker, the proposed bridge will function as a Nautical Landmark, guiding lakefront users to the mouth of the River, providing a visual and physical connection to the City. The design of the bridge is intended to recall the history of Chicago as a great shipping port and center of commerce. Recalling the Derek-like spars on the great cargo ships, the structure of the bridge is both functional and symbolic. Just as important as the imagery of the bridge on a large scale, is the aesthetic experience of passing under the structure from the river-view point. The design of the underside of the bridge reflects the shape of the hull of a graceful racing yacht hoisted into the air, as if in dry-dock. The beautiful proportions of nautical architecture are reflected in both the shape and structure of the bridge. The cable webbing design serves not only a structural purpose, but acts to weave together the two halves of the city, separated by the Chicago River, the most prominent urban feature in Chicago.

CONSTRUCTION:
The proposed footbridge is a cable-stayed structure with two supporting masts asymmetrically opposed to each other. The supports are of different heights and are located at the two-thirds point in the span. This provides for the required 250-foot clearance requested in the brief. The back-span of 120 feet is heavier, providing for a counterweighted, balanced structure.

The taller mast supports the long span and the shorter one supports the back-span. Each mast also has back-span cables. These cables provide a counterforce to the main force and also counter the torsion forces in the bridge deck created by the asymmetrical cable pattern. The railings are glass panels, lit from below, reflecting light onto the bridge deck.

OPERATION:
The bridge has been designed as a swing bridge, capable of rotating 180 degrees. The machinery is located in the foundation base at the two-thirds support point. The pattern of boat traffic tends to be in one direction at any one given time. The fact that the bridge can swing in two directions enables boats both exiting and entering the River to pull up next to the bridge without interfering with its operation when it opens. In the spring, it opens to the east, in the fall to the west. The bridge could be operated by the bridge tender in the main Lake Shore Drive Vehicle Bridge house.

The foundation support has been located such that ships coming from the Lake, through the Locks, have a straight-line course up the River.