Miami Pedestrian Bridge, Part VI 31

[chris snyder]

dik: "I converted the pdf to a png hoping to just paste the image into the reply"
I've used this pdf to bmp converter for years

https://www.tipard.com/free-pdf-to-bmp-converter/

Converted your doc, opened .bmp w/MS Paint (~6000x5000 pixels, 98MB), saved it as .jpg (after resizing to ~600x500 =>160KB) and it pasted quick/ok in reply (did not post, but used "preview" to chk)

 

[Cutterhead]

Here's a 40k a day traffic, 70mph double span bridge, that I traversed 4 times a week for 6 years while being built, while 50 year old one was being torn down. I was very impressed with how it all was coordinated on such a busy I-71 interstate highway. The new one is basically a concrete arch, built formed and poured in place. I don't see us going back to all steel bridges as a standard any time soon.

Truss bridges are another matter. The problem as I see it is in the gusset system. Concrete doesn't play nice with so many opposing forces in the nodes. The only way I see them being predictably safe is to have pre-designed, & tested/certified steel nodes, with concrete cover. The top & deck in concrete is not the issue.
Note the comparison shots of old vs new....

https://www.youtube.com/watch?v=pizGda1_x4M

 

[Retiredat46]

There were at least a dozen heavy chains and load binders installed between the middle of the canopy and the outer edges of the deck during the move. There were two on each side at each end with more mid-span. I didn't see anything about them on the drawings.

Would that rigging been capable of developing enough bending loads on the truss-to-deck joints to be of concern? Do we know anything about how tight they were and what procedure was followed for their installation?

 

[chris snyder]

Wanted to learn about concrete hinges and found this.

http://happypontist.blogspot.com/2014/07/yorkshire-bridges-3-smithy-wood.html

http://www.tallbridgeguy.com/2013/02/19/bridges-on-the-aston-sheffield-leeds-motorway/

It doesn't look very strong, but gets inspections "regularly". 158' long over 6 lanes of busy highway, out in the middle of nowhere (with a road overpass ~1200' south). Built in the 1960s, it was "designed as concrete Wichert trusses, possibly the first such designs in concrete". This design was used as it's in a mining area where foundation settlement is probable.

https://www.google.com/maps/place/S...8baee5db1031a29!8m2!3d53.4537712!4d-1.4539297

Comments are interesting, esp this:
"the average engineers nowadays use suites of computer programs that “do everything” for them without the need to understand what is actually going on inside the concrete, or how to use Mohr’s circle". There may be be other issues, but it will be interesting if we learn how much attention was given to the 11/12/deck connection.

 

[dik]

dik: "I converted the pdf to a png hoping to just paste the image into the reply" I've used this pdf to bmp converter for years

Thanks Chris... use Paint.net for graphics, and, can covert to many different formats, including *.pdf. and can do transparancies (sp?)... often *.dwg -> *.pdf -> transparent *.png for loading into excel and smath programs. I'll figure out some way to get around this hiccup. The smaller sized format may be one of them.

Dik

 

[SFCharlie]

I find the best info right here on eng-tips:

http://www.eng-tips.com/viewthread.cfm?qid=21490

"CONCRETE BEAM CAMBER"

 

[dik]

If you look at it as a beam, the horizontal component of force of the PT in the web would create a couple about the c.g. of the cross-section. This in turn would generate a moment and impact camber.

I have to think about this for a bit... stressing would occur to the tension web members. At the top, this would impart a horizontal force towards midspan, increasing the deflection. At the bottom, a horizontal force component towards the support, also, increasing the deflection.

Have to give this a greater thought...

Dik

 

[dik]

Chris: tried Tipard and it works well...

thanks, Dik

 

[epoxybot]

Yesterday there was discussion of establishing a timeline. I don't know if this video has been posted but it shows the percentage of completion up to Dec, 17 2017. Stars are on offer to anyone who can explain the need for the transparent quonset hut in the last third of the video. It just looks like a big waste of money. Link

Here is the best image I've seen of the PT Tensioning Ram. It gives a good since of scale. I'm not sure how much it weighs but I wonder if the work on #2 & #11 wasn't done on the day of the move because not enough forethought was given to fall protection and doing fall protection as poorly as they did on the day of the collapse, when so many species of officialdom where present results in a deferment. Link

It turns out that Sweetwater is a politically contentious little town. Link Lots of mud slinging, a mayor the is going up the river for some serious corruption. Link Property theft by the Police Dept. The ex-mayor is supposedly the shadow owner of a towing company that received a no-bid contract as Sweetwater's tow company. The city was charging well over $250 per tow. The police were targeting newer cars that had been fully paid off and when the owners failed to claim their cars in an allotted time, auctioning the cars off. There seems to have been either kick backs AND/OR skimming going on with this. An FBI investigation & an audit of the Police Evidence room found large amounts of impounded money missing and a subsequent investigation found that the 7 member PD had a "secret evidence room" filled with confiscated items, counterfeit merchandise & cash. 7 police officers for a population of less than 20K and a city of only 2 square miles. Towing seems to be a big source of cash for Sweetwater, so when a developer proposed building two multi-unit student housing projects with little to no parking, of course the city said YES!

Now, add to this that the Sweetwater student housing parking problem was going to be addressed by FIU, by allowing students living in Sweetwater to park their cars in the university's parking garage/s and the fee would just be a part of their rent paid by the landlord; this scheme doesn't really seem to actually fit the means vs need aspect of the TIGER program. The already built 109 Tower across the street from the university only has 25 parking spots for over 500 residence & half are reserved for staff. Still the much touted danger of crossing HWY 41 was totally conflated. Even the time lapse video prove that there is "Currently" no need for a pedestrian bridge. The developer that built the 109 Tower & the 4th Street Commons sold the 109 Tower but retains the mixed occupancy 4th Street Commons and based on Yelp it is rapidly becoming Student Slum housing.

I'm not against these kinds of partnerships but I object to Federal money contributing more than 50% to a scheme were the university profits long-term from dedicated parking funds that come to them through little to no investment of their own. When you look at projects like the 200 ft span Martin Olav Sabo bicycle bridge Link, including 2000 feet of of bicycle path earthwork for far less money that the FIU bridge, you have to ask some hard questions.

 

[Sparweb]

Dik,
The suggestion from Chris is good for starters but I'd avoid BMP graphics if at all possible.
(1)
When viewing the NTSB letter in PDF, nothing was stopping you from posting the URL. To do that you click on the address bar of your browser which usually highlights the address so that you can copy to clipboard (temporary memory in Windows or Mac). You can then navigate your browser to Eng-Tips and start your post. Paste (CTRL-V) in the body of the posting once you place the cursor in text where you want the address to be placed. If you want no more nuance or fancy business than that, then you're done. If you want it more fancy, well, you can use the "Link" button instead.

(2)
When you have a graphic on your screen and you want to share it, nothing is stopping you from hitting the PRINT-SCREEN button on your keyboard. That puts a screen-shot into your clipboard and you can then open PAINT or whatever equivalent there is on a Mac, then trim that down to only what you want.

(3)
I would have sworn that I've seen you posting various stuff in the past, and assumed you knew already.
Now that I've said my piece, be warned that there are on-line file conversion websites that offer lots of convenience, but in the background the server is keeping a copy. Word-search algorithms and humans can "review the contents" at will. I recommend you keep your work on your own computer, rather than in miscellaneous single-purpose downloads.

STF

 

[3DDave]

epoxybot - I've looked at the video several time and see no Quonset hut. Any hint on where in the video it is?

 

[SFCharlie]

The green house is in the lower right just north (edit: toward the viewer) of the canal:
(link will start at the correct time to see the greenhouse)

https://youtu.be/JiWhw9BZgII?t=307

 

[dik]

I would have sworn that I've seen you posting various stuff in the past, and assumed you knew already.
Now that I've said my piece, be warned that there are on-line file conversion websites that offer lots of convenience, but in the background the server is keeping a copy. Word-search algorithms and humans can "review the contents" at will. I recommend you keep your work on your own computer, rather than in miscellaneous single-purpose downloads.

I've posted lots of stuff with nary a glitch... something with my browser or the site is causing a little heartburn. I don't often use web based conversions... I sometimes use ClipConverter fot youtube clips. I can convert various file types on my home machine. I try to stay away from sites I'm not familiar with .

Should have noted that I don't use bitmaps... if any graphics format, usually use *.png.

Dik

 

[3DDave]

Thanks - the original video pops up a "next video" over that area for me. I need to find a way to shut those off; it's irritating; a number of videos are not quite over when those block the view.

 

[Retiredat46]

Epoxybot, I know it wasn't intentional, but the picture of the ram also shows the body of the deceased worker to the right of the man in the striped shirt. You may want to do some cropping.

I'd say the hut is for whatever project involved removing the houses.

 

[epoxybot]

Retiredat46 - Yeah, originally I was going to crop the photo and after having done so, I got to researching the weights of the PT rams on William's Forms & Engineering, when I returned to typing the post, I decided to just post the photo link having forgotten why I cropped it to begin with.

 

[jrs87]

Epoxybot, thank you for your great post. Do you have any information on how the ram works for PT bars? I know how they work for cables, but not solid bars. Is the plate and nut shown part of the bridge? Is the long tube a trumpet or part of the jack?

 

[jrs87]

"Currently" no need for a pedestrian bridge

New take on the bridge to nowhere: bridge for no one.

https://news.fiu.edu/2016/03/fiu-sweetwater-break-ground-for-bridge-to-the-future/98724

Quote from linked page: Though the exact number of pedestrians crossing SW 8th Street at 109th Avenue is unknown, it is estimated that more than 4,000 FIU students currently live in Sweetwater,

 

[jrs87]

I think this image answers my own question about jack.

 

[Ingenuity]

Do you have any information on how the ram works for PT bars? I know how they work for cables, but not solid bars. Is the plate and nut shown part of the bridge? Is the long tube a trumpet or part of the jack?

The one used on the Miami project was similar to the graphic you posted above (from Williams Form), except it was an enclosed-type (similar to the photo below), where the offset plate at the base of the jack has an internal racket/chain wrench and socket that enables the PT bar nut of the STRUCTURE to the secured/loosened. There is usually a short pull-bar and coupler within the jack/trumpet length to 'grip' the assembly. The nut/washer/bearing plate assembly at the top of the jack is to transfer load between the jack and the STRUCTURE bearing plate/s. Sometimes a load cell is placed at the top of the jack assembly to cross-check gauge pressure/force to an independent reference.