Question/Dilemma about High Bridge Construction...?

[NW Mailing List]

Hi Bob,

You certainly have a good eye to pick up that difference in track location.  I certainly had not noticed it and don’t recall reading anything about relocating the track in Vail’s notes. The only thing that occurs to me is your assumption that the centered track might have been for the construction period only.  However, I can’t think of a good structural reason why that night have been required.

 

I will keep an eye on the other responses that you might get.  Who knows, someone might have the answer.

 

I hope you are doing Ok and glad to see the spring arrive.

 

Skip

 

From: nw-mailing-list-bounces at nwhs.org [mailto:nw-mailing-list-bounces at nwhs.org] On Behalf Of NW Mailing List
Sent: Wednesday, May 07, 2014 9:04 AM
To: NW Mailing List
Subject: Question/Dilemma about High Bridge Construction...?

 

Guys
Can you help unravel this mystery?
Why are the High Bridge Rails off to one side of the towers now as opposed to directly in the center of the towers originally as seen in
the Vail pics attached below.

Bob Flippen

Moderator:
 http://nwhs.org/mailinglist/2014/20140507.hb.3.jpg
 http://nwhs.org/mailinglist/2014/20140507.hb.4.jpg
 http://nwhs.org/mailinglist/2014/20140507.hb.5.jpg
 <http://nwhs.org/mailinglist/2014/20140507.hb.22.jpg>  http://nwhs.org/mailinglist/2014/20140507.hb.22.jpg
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In Vail's photos, it appears that the bridge spans were laid in the center of the towers, as is clearly shown in the first attached file
(and many of his other photos).  The girders of the span run right across the two stiffeners (or whatever they are) in the center of the
cross-girder at the top of the bridge bents/towers.

BUT...  today the bridge spans run along one side of the towers, as clearly shown in the 2nd and 3rd attachments.  The spans do not run
directly over the two stiffeners in the center of the cross-girder.  And, in fact, in Vail's photo of the new and old bridge together (4th
attached), the girders of the new bridge clearly rest on the outside of the tower.  This makes sense since the bridge was constructed to
support two tracks.

So what am I missing???  I looks like the constructed spans on which the steam crane rode to install the top section of the bents and the
next bridge spans isn't in the same position as the final bridge spans!  Were these spans temporary to support the installation, and then
moved?  Nothing is mentioned of moving the spans later, and that seems like it would be a waste of time and energy.  And Vail's photo of the complete bridge shows the spans in place on the towers as we see them today.  I'm obviously missing something!

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