Friday, September 12, 2014

Moving a Bridge and Satellite Image Ages

(Update: This project is done now.)

The CREATE GS15a project was to add grade separations around Torrence Avenue and 130th Street. Scroll down to the bottom of the above referenced web page to see before and after renderings of the project. The new blue truss railroad bridge is 394-feet long, 35-feet wide, 63-feet high and weights 2150 tons. (Other sources say 398-feet long and 2350 tons.) It was built offsite...

...and then moved into place in less than 3 hours. The brown bridges in the background that you see at the beginning of the video is the old alignment that is being replaced with the blue bridge. The following is a time lapse of the move. CREATE's video has more description and less action.

I could not find a picture of cranes lifting the bridge on top of the mover scaffolding. Over 2000 tons strikes me as a lot. I found a load chart. A quick scan of the Ton column indicates that some crawler cranes can lift over 1000 tons. (I'm sure it was lifted with at least two cranes, one at each end.) But they are monsters. The more typical cranes like the one used during construction above are in the range of 100-300 tons. Now that I'm thinking more about the subject, maybe the moving contractor used hydraulic jacks and cribbing to raise the bridge, and then they drove the movers under the bridge. The movers themselves have an 18-inch lift, which is enough range to lift the bridge off of cribbing and then to lower it onto the bridge abutments.

When I looked at the Google satellite image, I noticed the bridge was already in place. So that image was taken since the move day, Aug. 25, 2012. Since I don't know when Google will update their images again, below is the image I found. In the image, they have not even begun to dig for the underpasses. I notice in the status map that GS15 is still in the construction phase. So this site goes onto the Sundays field-trip list.


I've noticed in the past that Google seems to have the newest images so I was curious and checked the other images I use.

In Flash Earth we can see that construction has begun. They have poured the piers and retaining walls for the new alignment and have prepared the ground where they will erect the new truss. Bing's image is so old that construction has not even begun. (I have used Bing's age to my advantage in the past to see what stuff used to look like.)

Bing's new software provides an option to turn off labels. And I've noticed that their aerial photos are about the same date as Google's, but (fortunately) their birds-eye view maps are still old. Their current aerial is the same age as the above FlashEarth version. I gave Bing feedback that I wanted an option to turn off labels, and a little later I noticed that option.

Newer Birds-Eye View Software, Same Images

No comments:

Post a Comment