Ferry Dock Collapse 13

[dik]

"At least seven people were killed and several others injured Saturday after part of a ferry dock collapsed on Georgia’s Sapelo Island, according to the Georgia Department of Natural Resources.

It happened as crowds gathered on the island for a celebration of its tiny Gullah-Geechee community of Black slave descendants.

At least 20 people were plunged into the water when a gangway collapsed on the visitor ferry dock shortly before 4 p.m., Georgia DNR Capt. Chris Hodge said at a Saturday night news conference. A McIntosh County commissioner previously said a boat hit the dock but a DNR spokesperson later told The Associated Press there was no collision and it is unclear why the dock collapsed."

https://www.cnn.com/2024/10/19/us/sapelo-island-georgia-boat-dock-collapse/index.html

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[Sym P. le]

A quick look yields the Sapelo Purchase Order.

I outlined the timeline of project progression earlier (Page 5, Wednesday at 5:21 PM). This is a quote and P.O. for the Meridian landing (Phase III), not the failed Marsh landing gangway. The question is whether the documents and overarching agreements pertain specifically to the failed structure. The previous invoice I posted indicates the contractor acquired the Marsh gangway to fulfil terms of their contract. All of these documents are valuable to understand the environment in which the contract was hatched. The quote you posted includes a price for stamped drawings and the P.O. includes same.

 

[Garbage1]

SymPle sorry if I reposted anything you already posted, but I must admit this Web Site makes it very difficult to keep things straight. You only get a few posts on anyone page, and each page loads slowly, and you have constantly jump back and forth between way too many pages to find previous posts then back to last page where you are trying to post a response! The design waste vast amounts of screen space, and repeats the OP at top of every page which waste more space...... Once I read thru all the posts, I have not bothered to go back and try to ensure I have not duplicated some previous post.......
Then a lot of space at bottom of page is wasted with so called "similar threads".
Also when logged in there is a post page at bottom of pages on each page, which is confusing at times.
Lots of Continuous improvement effort required, if that is possible with base software.....
Does not appear a lot of seasoned users/customers had any input to the design of this (whatever you want to call it)......

 

[Sym P. le]

No worries, this new forum does not work as efficiently as the old, at least from my user perspective. It is much more difficult to track long threads and even referencing previous posts takes forever, at least if I want to reference the poster and time of post. Thus when I state I posted "earlier", it's because I'm being lazy, not intending to be terse. That reference was to Page 5, Wednesday at 5:21 PM.

You didn't double post. I was trying to re-emphasize the progression of the Sapelo Island project as a whole through various phases as quoted and then executed.

Regarding "SECTION 05555 - ALUMINIUM MARINE STRUCTURES", that was an addendum (Addendum No. 2) to the Specs for the Phase II bid package. It created some confusion with the "SECTION 355113 - CONCRETE FLOATING DOCK SYSTEMS AND GANGWAYS". The distinction is that Crescent also has aluminum docks available and I believe they are used for smaller installations. The Bellingham concrete docks are preferred for larger heavy duty installations. Both are envisioned as systems c/w gangways etc.

Phase II Specs and documents are found in the folder "Bid Documents" (They refer to Marsh and Meridian as they were priced together before Meridian was deducted). The Phase III Specs and documents are found in the folder "Meridian/Bid Docs" (When the Meridian project was rebid).

 

[LittleInch]

Each post has a number in the right hand side so you can just use that?

So it seems to be 20 posts per page. I'm asking for the number or page to be able to be varied so you vac choose to get 20 or 50 or 100. Hasn't happened yet but might.

On a phone it loads much faster than before this way so that is better.

On the disaster, I think it will be found that the gangway was longer than ones they normally produced to limit the angle at low tide and no one actually designed it, they just bought a stretched 60 ft one, and never realised the trusses were different.

 

[Sym P. le]

It's not so much that the truss type was different (the Howe truss is actually more suitable than Pratt), it's that an "L" or inverted "T" has limited viability in any circumstance. That two different types were employed in essentially the same project just makes the head scratching more ...

 

[Garbage1]

It's not so much that the truss type was different (the Howe truss is actually more suitable than Pratt), it's that an "L" or inverted "T" has limited viability in any circumstance. That two different types were employed in essentially the same project just makes the head scratching more ...

Howe more suitable for aluminum than Pratt??? My take is Howe is better suited for wood with larger diagonal members in compression, and Pratt is more suitable for aluminum/steel with longer smaller diagonals in tension??? EDIT: In terms of efficiency and lower costs a Pratt looks the winner for aluminum. My concern is Pratt sized members in Howe configuration will not support equal loads. Perhaps Howe distributes loading better under certain conditions. Either one can work if members sized according to configuration for specific material used.

I will attach an email string between Crescent Equipment and GaDNR. There were prior complaints that caused concern from GaDNR and required inspections. It is interesting to note that the loud popping and broken welds in attached email traffic was centered around 15-20' from the floating dock, or in the area that failed........
Camber process after tack welding decking in place.....see quote More interesting information contained in attached email traffic.......

Ty Barrow/Crescent Equipment Quote from attached email.
"What I would like to ask is that we let that one sit for a bit longer The decking is spot welded to the
stringers before the cambering process, and it is now out there 24/7 testing that camber. Its possible
that one section (for whatever reason) needed relief. I would like to go out and re-inspect it later this
year to make a conclusion."

 

[Sym P. le]

This is why more eyes are better. I hadn't accessed fully absorbed that file yet. I wonder what issues can arise in the cambering process.

As to the truss type, it was my impression that the Howe distributes the top chord compression across the length of the structure compared to the Pratt which concentrates the force at the center. Since buckling is likely the failure mode, that is the factor of greatest concern in this instance.

 

[Garbage1]

Camber would have pre-stressed the structure. Wonder how they accomplish this task with an 80' long dock? Hot or Cold forming?

I don't disagree with your Howe top chord compression handling, and I would argue that member was not sized properly either for the Howe configuration. My guess is actual designer did not understand difference between round and square tube load capacities.

The lack of engineering and understanding the affects of geometry changes are the issue along with quality control; rather than whether Howe or Pratt design works best in this situation.

It is also interesting that GaDNR had no engineering evaluations conducted by Ga's engineering division or their contract engineer specialist. Rather they tasked the 'biased' original manufacture to inspect his pre-fab design and built marketplace product.......When you buy a Pre-FAB product on just a Purchase Order, you get what you pay for it seems.......or in this case, more than you bargaining for.....

This image, posted earlier, of a Howe design has very different member sizing than the Sapelo 80' Howe.

 

[Sym P. le]

The supposed engineering drawings which were invoiced and paid will be an issue. I wonder if they will ever see the light of day.

 

[Garbage1]

Based upon the fact that St. Mary's investigation, conclusions and action taken has not made the light of day, I don't expect Sapelo's to make it either. IMO, the documents they are withholding will likely not shine favorable on anyone involved (Georgia Government Agencies, Crescent Equipment, nor probably the supposed engineering stamped drawings for Crescent's 'Modular/Expandable All-In-One' gangway design.

 

[FacEngrPE]

Setting camber in walkway like this can be done by blocking the lower cord to the desired shape before welding in the diagonal members. For a structure like this camber is mostly cosmetic ie it does not change the member stresses.

All of the questions regarding correct engineering calculations which could have been a deliverable, can be short cut by performing an acceptance proof test. Perhaps 2X design load.

Maritime Safety Services; INSPECTION AND LOAD TESTING OF ACCOMMODATION LADDERS AND GANGWAYS

Periodic proof load testing of a maritime vessel’s “means of embarkation and disembarkation” (accommodation ladders/gangways & davits) is required in accordance with IMO Regulation II-1/3-9 of the 1974 SOLAS Convention, and as per the Guidelines for Construction, Installation,
Maintenance and Inspection/Survey of Means of Embarkation and Disembarkation, effective January 1, 2010.

The SOLAS regulations require that the ladders and gangways should be static proof load tested and function tested following initial installation and then at 5 year intervals per SOLAS I/7 and I/8.

OSHA Code

29CFR1915.74(a)
Access to vessels afloat. The employer shall not permit employees to board or leave any vessel, except a barge or river towboat, until the following requirements have been met:

29CFR1915.74(a)(1)
Whenever practicable, a gangway of not less than 20 inches walking surface of adequate strength, maintained in safe repair and safely secured shall be used. If a gangway is not practicable, a substantial straight ladder, extending at least 36 inches above the upper landing surface and adequately secured against shifting or slipping shall be provided. When conditions are such that neither a gangway nor a straight ladder can be used, a Jacob's ladder meeting the requirements of paragraphs (d) (1) and (2) of this section may be used.

If employees had been on the gangway, OSHA would likely have become involved.

 

[Denial]

That reference was to Page 5, Wednesday at 5:21 PM

This intra-thread referencing is now quite a pain in the RRRs, and I have already raised it in another forum.
» Once a post is more than a day or so old, its date is shown but its time no longer appears. (Even more wasted white space.)
» I think, but have not yet confirmed definitively, that the date&time displayed when a person views a post has been converted to the viewer's time zone. So the date&time shown to YOU will usually NOT be the date&time shown to ME.

Grrrrr.

 

[Sym P. le]

... and the time stamp disappears so now I don't even know what I talking about. !?!?

Ok. Found it. Page 5, #97, starting with "Some clarification."

If you press and hold the posting number you get a link which you can apply liberaly or conservatively, which ever way you lean. Or you can just be a pirate, RRR!

https://www.eng-tips.com/threads/ferry-dock-collapse.523612/post-9032544

Edit: Fixed applying the wrong link. RRRRR!!!

 

[GregLocock]

"All of the questions regarding correct engineering calculations which could have been a deliverable, can be short cut by performing an acceptance proof test. Perhaps 2X design load."

For man rated stuff in Oz I think it is 4x by annual test and 10x by calculation. For things that don't get used much this annual test is the major contributor to their fatigue life. Not my field, I may be wrong.