Bridge too low...

One thing that drives me nuts is when an engineer designs something and tries to use every single gnats hair of space.

That bridge was brought up under the thread: oops.

Could've been one of a dozens reasons. Who wouldn't have ballast, tie, and top of each rail.

2014 there was a similar situation in Mt Pleasant, Tx.

http://www.dailytribune.net/news/bridge-repair-tagged-at-million/article_fb6fa99e-7ca9-11e3-bfb5-001a4bcf887a.html&apos ;">Realignment of Highway 271

Appear to be an architects mistake. Top of beam measurements should have been to bottom. Or, otherwise with the engineering plans. Happens often here, arch plans never match engineering. And we're trying to build muti-million dollar oceanfront homes, interchanges, and such.

Tommy Young, post: 374838, member: 703 wrote: One thing that drives me nuts is when an engineer designs something and tries to use every single gnats hair of space.

They're not. The specification for railways includes a "clearance box" which includes space above and to both sides of the largest standard railcar in North America. Of course the problem is that overhead objects might settle a bit, and objects to the side of the tracks might get moved or have stuff added to them etc.

A Bridge Too Low.

Chief Engineer Marshall Montgomery, in an audacious plan, designs a bridge to have less than 1mm of clearance.

It didn't work, unfortunately.

The Mt Pleasant error is reported to be that the highway elevation and RR elevations were from two different sources.

They are still debating which one is right.

The obvious problem was that neither connected into the source information of the other to see if it would fit in the first place......

http://www.delawareonline.com/story/news/2016/05/23/newport-bridge-too-low-deldot-must-correct-mistake/84553084/&apos ;">Spin it baby, spin it....

Blah blah blah, They designed the clearance incorrectly, period.
As stated above there should have been a lot of data collected....

the explanation of checking clearance before the deck was placed is BS... everyone knows they have to account for loading when checking elevations-

"Benton stressed that he is speculating on the cause as DelDOT has not made a definitive determination."

Steve Boon, post: 374856, member: 416 wrote: They're not. The specification for railways includes a "clearance box" which includes space above and to both sides of the largest standard railcar in North America. Of course the problem is that overhead objects might settle a bit, and objects to the side of the tracks might get moved or have stuff added to them etc.

Certainly the "clearance box" has more "clearance" than the height of a rail...?

Jim in AZ, post: 374878, member: 249 wrote: Certainly the "clearance box" has more "clearance" than the height of a rail...?

It has more clearance. But it has a min safe number to guarantee that the safety margin clearance is achieved. RRD/NTSB holds to that number; no exceptions.

Three words...should've scanned it.

A point cloud would clearly show rails, ties, ballast, etc.

John Hamilton, post: 374883, member: 640 wrote: Three words...should've scanned it.

A point cloud would clearly show rails, ties, ballast, etc.

One word... communication.

I'll wager that the shots on the top of rail were made but they were not included in the DTM surface (which is proper), and clearance calcs were made relying on the surface.

Mark Mayer, post: 374888, member: 424 wrote: I'll wager that the shots on the top of rail were made but they were not included in the DTM surface (which is proper), and clearance calcs were made relying on the surface.

Perhaps somebody forgot to thaw the point layer containing said top of rail shots?

I'm guessing two different sets of elevations from different jobs, or one benchmark not accounting for earths curvature.

John Hamilton, post: 374883, member: 640 wrote: Three words...should've scanned it.

A point cloud would clearly show rails, ties, ballast, etc.

The bridge was built in 2011- back off another 4 for project design and development, I'd estimate the preliminary survey was done about 2007, a bit before scanning was the rage it is now. I doubt deldot had a scanner to use at that time....

My point is that as scanning becomes more common, there will be a lot more data available for design. We use the scanner for all topo's now. It doesn't totally eliminate total station or RTK shots (usually), but it does make everything much more clear when creating a drawing in the office. And it has saved a long trip back to the site when something was missed with the total station.

So, curious...how many have a scanner and do you use it for standard topo's?

John Hamilton, post: 374925, member: 640 wrote: So, curious...how many have a scanner and do you use it for standard topo's?

You are right. I saw the value of these black boxes when I first saw them demoed in 1998 +-. I never wanted to be a point cloud processor, so I purposely stayed away from them but I think that day is quickly coming to an end. My 2 cents, Jp