Bridges to Nowhere – for now

BRIDGES to NOWHERE –For Now

Pedestrian bridges, often called foot bridges, have been both separate from and part of vehicular bridges. As separate structures they were often constructed in rural or wilderness areas tied to trails rather than roads and were designed with a rustic look.

However, pedestrian bridges associated with urban areas are in demand now and often include bicycle usage. As shown by the three bridges presented here, the reduced scale of  urban bridges and their proximity to human beings and nature no longer call for a rustic design,

Despite the fact that these three bridges have gained praise and publicity, the present economic downturn has given them uncertain futures. Hence the title “Bridges to Nowhere—so far.”

THE ST. PATRICK’S ISLAND BRIDGE, CALGARY, CANADA

Rendering of the St. Patrick's Island Bridge, Calgary, Canada

The St. Patrick’s Island Bridge in Calgary was designed in 2009 by Endres Ware* and Ammann & Whitney**, as a gateway to the activities of the island’s Centenary Park. The two-part bridge will also frame views of Calgary and the Rocky Mountains.

The bridges connect to a central platform located where they meet on a mound of earth to be constructed on a site in Centenary Park. The rendering shows a curved path on a mound leading to a ramp lifted up and attached by some of the cables to another land form behind the main pier. The bridges’ low arches, also visible in the rendering, rise just high enough above the underlying flood plain to avoid possible flooding but will not block views of the surroundings.

The bridges’ structure allows the weight of the concrete decks to be carried by a series of main cables running up to the two masts from which backstay cables transfer the deck’s weight back to the ground.

Site plan for St. Patrick's Bridge, Calgary

The two separate cable-stayed bridges, one longer than the other, span the Bow River flowing by the city of Calgary.

Night rendering of St. Patrick's Bridge, Calgary

The masts are bent to reduce their height. The main cables are strung evenly along the length of the masts; the backstay cables, gathered near their tops, are “harped”, meaning that the cables have different lengths.  They cables splay from the top of the mast downward and extend to the adjacent bridge, which reduces the amount of force necessary for their anchorage and allows the bridges to brace each other horizontally.

The bridges appear to bow to their respective destinations, the city and the neighborhoods on the riverbanks. One hopes that users from both places will be able to respond with their feet to their salutes in the not too distant future.

THE LEWIS EATON PEDESTRIAN AND BICYCLE BRIDGE

The Lewis Eaton Bridge

The Lewis Eaton Bridge project began in 2007 and was designed to enable pedestrians and bicycles to cross the San Joaquin River at a location near Fresno west of Highway 41, which is known as “the Yosemite Freeway.” The bridge is part of the efforts of The San Joaquin River Parkway and Conservation Trust to conserve the river, rehabilitate the surrounding land in the 100-year flood plain, and connect the City of Fresno with Madera County. The commission for the project was awarded to landscape architects Patrick and Jane Miller of 2M Associates as the prime and architects and  Endres Ware for the bridge design.

Site plan for the Lewis Eaton Bridge

Visible from Highway 41 as well as from the Fresno and Madera County river bluffs, the bridge will be a landmark for the San Joaquin River Parkway. A multi-use trail located on or parallel to the existing vehicular access road parallel to the river will provide an entry to the bridge.

The soil characteristics of the site were a major challenge to the design process. Although the ground on the west bank is stable the landing is on an island that may wash out in heavy flooding. The dry riverbed is not suitable for a landing because of possible flooding and poor soil conditions.

Diagram of the cable-stayed structure of the Lewis Eaton Bridge

The cables surrounding the bridge deck will provide a sense of enclosure and increase the deck’s stability. They will also create a “gateway” to views of the river by splaying down from the mast to the approach deck which passes under the it.

A gathering place for pedestrians at the bridge access path.

As the ramps descend from the mast to the ground, they will create a small area for people to gather in the tower’s shade .

Although Endres Ware and 2M Associates were commissioned to design the bridge and its surrounding landscape in 2010, a lengthy permit process of five years or more must be concluded before its construction begins. Although the design may change during the time required to gain final approval, one hopes the vision depicted in these images endures.

THE WEST END BRIDGE ADDITION FOR PITTSBURGH, PENNSYLVANIA.

The international competition, sponsored by ALCOA, for the West End Bridge Addition over the Ohio River in Pittsburgh, Pennsylvania,  was held in 2006. Endres Ware’s winning design for a

The West End Bridge and the proposed addition, Pittsburgh, Pennsylvania.

new pedestrian crossing to be connected to the historic Bridge over the Ohio River respected the existing bridge. while updating the structure with a dramatic suspended bridge that will improve access for pedestrians, cyclists, and boaters to new recreation and park facilities.

Site plan of the existing bridge framed by the new pedestrian addition.

There are two access points for the bridge. One is a ramp on the bridge addition that runs down to the park ground below. The other is from the historic bridge at its westernmost tower. Pedestrian and bike lanes run from there along the south side of the bridge until they reach the shore.

A Rendering of the new pedestrian addition to the West End Bridge.

There are two access points for the bridge. One is a ramp on the bridge additionthat runs down to the park ground below. The other access point is from the original, historic bridge at its westernmost tower. Pedestrian and bike lanes run from there along the south side of the bridge until they reach the shore.

For Riverlife, the organization that managed the competition, the West End Bridge project is a top priority, and although funding for the bridge during the slow economy has been tricky, 70% of the work on the surrounding park lands has been completed, and hope for the rest is growing.

*Endres Ware, architects and engineers <endresware.com.

**Ammann & Whitney, bridge engineers <ammann-whitney.com>