Denver Millennium Bridge


An exercise in levitation

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.

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.

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.

A note on big hardware

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.

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 to the Google Maps view.

Sights and Sounds

February 21, 2011

Denver 110221 Mbridge Base med.JPG

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

Denver 110221 Mbridge Anchors med.JPG

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.

Denver 110221 Mbridge Suspender med.JPG

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

Denver 110221 Mbridge Mast ctr med.JPG

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.

Denver 110221 Mbridge Deck med.JPG

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 photo.

Cc by sa 80x15.png 2011 D A Ayer