2011-02-21: More bridge samples, these from Denver’s impressive cable-stayed Millennium Bridge pedestrian walkway.

The Denver Millennium Bridge opened in 2002 as an extension to the Sixteenth Street pedestrian mall. It’s a pleasant three-block walk northwest from the renowned Tattered Cover Book Store which, in 2011, was pretty much at the end of the mall. It appears that won’t be the case for long, as construction projects abounded here and elsewhere in Denver when we visited.

Going there

We’ll be experimenting with how to post GPS coordinates in a device-friendly format (a link to send them to your phone?), but for now we’ll settle for a link. First, get to Denver. Here’s the Waymarking.com page with GPS coordinates and a bit of background on the bridge.

An exercise in levitation

Late mid-morning, there is little foot traffic on the bridge deck. Construction and heavy equipment noise competed with the wind as prime audio drivers. Amplitudes were pretty low, so these samples were normalized before posting; the usual comments about an—and apologies for—a more audible noise floor apply. In the case of the anchors, timbral variation is actually much more noticeable than the slight variations in pitch.

February 21, 2011

The bridge’s main mast is readily visible from many places around the city, and it’s a bit surprising to learn it is not some enormous structure but a pedestrian bridge over rail lines near the South Platte River. The broad upper deck will presumably extend the Sixteenth Street pedestrian mall seamlessly once the construction finishes and the orange safety cones are removed at street level.

The central compression mast and network of cables form the focal point of the bridge.

File Denver Millennium Bridge 00 at freesound.org

The five main anchor cables fan out from the mast and down and plot a graceful arc at the base. We counted them starting closest to the mast.

File Denver Millennium Bridge 01 at freesound.org

File Denver Millennium Bridge 02 at freesound.org

File Denver Millennium Bridge 03 at freesound.org

File Denver Millennium Bridge 04 at freesound.org

File Denver Millennium Bridge 05 at freesound.org

Up on the pedestrian deck, all the cables are suspenders, although the tensioning mechanisms are similar.

File Denver Millennium Bridge 06 at freesound.org

One of the aspects of bridge design and engineering that fascinates us is a tradition of simply scaling up traditional hardware to do a big job. These tensioning mechanisms look like magnified and slightly streamlined bicycle brake cable ends, and they imply the existence of 12″ open-end wrenches. Such things apparently do exist and are used regularly in civil engineering projects; we just seldom see them lying about.

The central compression mast is easily accessible near the south elevator on the upper deck. There was more heavy equipment noise at this spot than at the base below.

File Denver Millennium Bridge 07 at freesound.org

The suspender farthest from the mast is beyond reach of pedestrians. The sample is from the longest readily reachable cable towards the north, one of those visible toward the left in the last photo.

File Denver Millennium Bridge 08 at freesound.org