Miami Beach, Champlain Towers South apartment building collapse, Part 03 148

[SFCharlie]

A continuation of our discussion of this failure. Best to read the other threads first to avoid rehashing things already discussed.

Miami Beach, Champlain Towers South apartment building collapse

Miami Beach, Champlain Towers South apartment building collapse, Part 02

Thank you

SF Charlie
Eng-Tips.com Forum Policies

 

[Retiredat46]

My theory is that the roof column anchor that was designed to go at the top edge of that diagonal tear was load tested that day and weakened the stair sheer wall, which fell later than night/early morning. Thus this might be the trigger that started it all.

I think the bolts that hold the anchor are tested with a device that applies the load to a very small area before the anchor itself is installed. See this post above: Ingenuity (Structural) 2 Jul 21 19:42 It's very unlikely this sort of test could have done enough damage to result in a large section of the wall falling spontaneously hours later. The bolt itself would come out because of adhesive failure, or a small section or concrete around the bolt/epoxy would have come out, both immediately obvious and of limited consequence.

Questions:
Do we know what the anchor for that location looks like? It doesn't seem like it would be the same as the post anchors.
Why are the post anchoes so tall? If the load on the anchor is usually in the horizontal direction, the height provides more unnecessary leverage and load on the anchor bolts on the opposite side.

As a recreational climber, I'm very interested in tie-in points. I think I'd be more likely to put my rope around the base of the anchor post than use the ring.

 

[bones206]

Notice in the demolition video, looking south - the parapet over the x04 living room came free completely and yet remained intact. As if it wasn’t attached at all.

I believe this photo shows a parapet laying on edge on top of the cantilevered portion of the roof. The canine rescuer is standing on one of the tie columns, which provide the only attachment for the parapet. Drawings indicate the tie columns are spaced at 20 ft. It looks like the edge of the roof slab popped off when the tie columns rotated and the dowels pried out. Not implying this was a collapse instigator, just good photo evidence of that particular structural connection.

 

[FacEngrPE]

Testing of anchor bolts during assembly is a prudent measure, I always specify that with glue anchors (critical anchors get 100% pull testing, non critical anchors can get skip lot testing).

However in the case of window washing anchors, it appears that anchor bolt testing may not satisfy the OSHA testing requirements. I completely agree with the discussion above that placing a 2500 lb load between two anchor stands could create a loading condition on the roof that is outside of the loads considered for design.

OSHA Interpretation of International Window Cleaning Association/American National Standards Institute (IWCA/ANSI) I-14.1-2001 Section 8.1.3 testing requirements

 

[jar546]

This is my first post on this forum. I have lurked for years and used links to some of these discussions as talking points. Other than the conspiracy theorists that take away from discussions like this, this particular thread, all 3 of them, has been enlightening, informative and helpful. I have particular interest in this thread because I am the Building Official for a south Florida beach town with 23 high/mid-rises on the beach front, many built around the same time. There are another 20+ high/mid-rises across the street but not directly on the beach, they front the intracoastal waterway.

At any one point, we always seem to have 1-2 or more condos undergoing concrete restoration. Many times it involves mostly waterproofing and balcony work, but often it becomes more involved. One particular thing that we have noticed is that during restoration the NE corners of the buildings that are on the beach are significantly more deteriorated than other parts of the structure. We see this because often those on or near the NE corner must replace their sliders and windows that had to be removed due to the restoration. It is also not uncommon for an entire balcony to be removed and poured fresh. Wrap around balconies in the older condos end up looking like swiss cheese. See example below.

Building Official, FL & PA
The Building Code Forum

 

[MOJOJOHN]

What is a "trigger" and what is the "cause" of the collapse?

I propose that they may be two different things like the straw (trigger) that broke the camel's back (broken back is the collapse.)

I also feel that it is likely that the ground floor columns were degraded due to salt water exposure when the parking garage was frequently flooded as reported by residents.

The trigger may have been the loading of the roof with material, a car hitting a column, the collapse if the pool deck patio with its own trigger and many other possible triggers.

Based on my over 50 years of high-rise design (up to 40 stories high), high-rise inspection and concrete remediation in South Florida, It is my my opinion based on review of photos, plan,
our ETABS calculations and reports, that the building would not have collapsed due to any of these triggers if the columns had been in original condition. (Yes, we did observe under design in wind and gravity loading of the original
structure. We also concluded that a failure of the remaining structure after the first collapse was not safe under 35 mph sustained winds with the accompanying higher wind gusts, based on a rough assumption of lower column conditions.)

Based on all of the above, though it now appears that the Tropical Storm will mostly miss us here, I agree with the decision to implode the building to control its direction of fall and protect the rescue teams.

Yes, evidence was likely lost due to the implosion, but life safety of rescue personnel must always take precedence over property matters.

What is the solution to minimize future failures? There are many to be considered:

1. Enforce the current requirements by the Florida Board of Professional Engineers that work on Threshold Building (See my previous post for definition)be done by qualified engineers.
The 2018 inspection of this building was done by properly licensed P.E.,S.I. engineer, but the 2021 inspection of Crestview Towers, now evacuated as not. (I look forward to seeing the report tomorrow from another engineer that says Crestview Towers is OK.)

2. Educate Building Department on who may do 40 year inspection of threshold buildings, inspection and remediation work on Threshold Buildings with serious structural damage.

3. Change the Florida Building Code to clearly define 2 above and to revise Substantial Structural Damage to include serious damage to any one or more structural members that cause a collapse if lost.

4. Shorten the inspection cycle for building exposed to seawater flooding.

5. Consider ACI and other changes that would require ground floor columns exposed to potential salt water degradation to stand up even if the 2nd floor is lost.


That's it for now, but it is not nearly enough. The world of structural engineers is going to change. It is up to all of us to participate in the discussions to make sure the changes are going in the right way.

Regards,

MojoJohn P.E., S.I. , Former Urban Search and Rescue team member.

 

[Retiredat46]

I completely agree with the discussion above that placing a 2500 lb load between two anchor stands could create a loading condition on the roof that is outside of the loads considered for design.

Thanks. If that's what was actually done, Thermopile's theory becomes much more plausible.

 

[gonefishing2]

As far as OSHA required testing of fall protection column and roof anchors, testing the individual bolts proves the bolt and concrete hold, but only testing of the completed assembly from the fall protection eyelet proves that the whole mounted assembly meets subsystem requirements in that location. The design drawings are a mess on load testing procedures and if OSHA not specifying method of test, it is unclear how each contractor chooses to conduct the test. A stain gauge between two completely installed roof/column anchors would test 2 connections at a time and be the easiest and fastest way to proof test anchors, and should be witnessed by the city inspector, who was on site that day for this apparent reason.

 

[Murph 9000]

4. Shorten the inspection cycle for building exposed to seawater flooding.

It's not just flooding. It depends on the specific beach and the way the ocean hits it, but you should look at what a strong wind and high spring tide can do on a leeward shore. About gale force 7 or higher winds are likely to carry salt spray a significant distance past the high water mark, and possibly high above the ground. I've known high spring tides and a good gale/storm to cause waves breaking against a sea wall to go clear over the roof of beach bungalows (and the wall facing the beach has a constant stream of salt water running down it). Even without waves breaking hard against the shore, gale force winds pick salt spray off the surface and carry it with them. Each beach is unique, some will be worse than others, some will need quite specific winds to really get going with spray.

 

[gonefishing2]

I have not checked the original design drawings for steel reinforcing requirements in stair shear wall, but from pictures and way it tore diagonally, it does not appear that was not much if any steel grid in that shear wall, or rebar corner ties to connect failed panel to the perpendicular panel joint. Without steel or adequate steel grid, the potential horizontal loading of the wall anchor in a direction outside the normal load path could causes the usual tearing vector, if rebar grid is absent. Diagonal tearing does not seem likely from connector assembly test, if wall had been reinforced and tied to surrounding pours.

 

[la belle vie]

I would add to MOJOJOHN's list that inspection reports should be required to more fully describe failure scenarios that could occur based on the building design, and then postulate a sequence of events where the observed deficiencies eventually lead to failure.

 

[gonefishing2]

Please let me say, my theory is based upon reading all posts in this forum for the past week, and diving into available public information. My theory is a systems theory, and requires all the great input provided in this forum by subject matter experts to piece together this theory. pieces of this theory have been touched on many different ways in this forum, and all I did was piece together the clues that seemed to align into a system theory answer. We still have no idea what was exactly going on that day on the roof, or all events leading up to this failure. But it sure seems odd that day after first load tests, you have collapse of perhaps under nourished building structure, with 40 years of neglect and cosmetic patching to hide some of the underlying damage and defects.

 

[dik]

Recriminations are easy... this was brought to their attention 3 years ago.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[dik]

A main tenet of Engineering Associations is to look after the well being of the public; we have failed, and perhaps 150 people died because of that failure.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[SFCharlie]

I have chosen to view the controlled demolition as an experiment on the structure (yes, evidence was lost).
Watch the Surfside demolition from four different angles
Surfside condo building: before, during and after the demolition
These contain some slow motion and close-up views including the columns punching through the roof.

The British Sun still has the live feed they started for the demo up on YouTube watch the rescue.
Collapsed Surfside condo to be demolished before Storm Elsa hits Florida

SF Charlie
Eng-Tips.com Forum Policies

 

[saikee119]

Lukeuk99 (Computer),

Don't see parallel between UK's Glenfell Tower with Florida Champlain Condo. There heaven and earth differences.

(1) Glenfell is a public housing owned by the local government for housing the poor. Its largest 4-bed flat has under 1,000 sqft accomodation and has no resident parking facilities. Champlain condo is for the very rich as even a one-bed flat has 1,200 sqft accommodation and the minimum car park width is 10' with 113 parking spaces.

(2) Champlain Condo has collapsed structurally. Glenfell Tower is still standing and not collapsed despite suffering a huge fire that burn for 60 hours.

(3) Glenfell Tower as a public housing with no profit/commercial consideration is robust in design. It has a solid shear core with outside perimeter columns each about 42"x42" (metric size 1050mm x 1050mm). Champlain Condo is a private development. It has open shear walls and the biggest columns are 24"x24" (at the basement level). The columns in the collapsed section at the basement level are significantly smaller. It appears the section remained standing after the collapse were supported by the 34"x24" columns.

(4) Don't know the reason why Champlain Condo collapsed yet. The fire in Glenfell Tower was self-inflicted by the owner as the building was original a naked concrete structure that cannot be burnt or catch fire. The local government owner tried to beatify its appearance by approving a combustible cladding on the outside that was not made air-tight. When a fire broke out in one unit the heat cracked the window pane and the fire could migrate behind the cladding, using it as the wind tunnel like the chimney effect, to reach to other levels "externally from the ouside". When the fire got close to a corner the glass panels cracked on both legs of the corner (90 degree apart) and the fire was drawn into the flat due to pressure differences. It was quick rare to see fire could travel from the outside into the inside to spread floor by floor until the building was engulfed for 60 hours. Thus Glenfell tower is just a fire problem which is wholly within the architect department. but Champlain is likely structurally related so the structural engineer and the Condo management people may have some sleepless nights.

 

[Lukeuk99]

saikee119

Some corrections to your post ...

- Grenfell tower was actually owned/managed by a residents management company, it was NOT owned by the Council (Kensington & Chelsea Council), although they had seats on the board, they did NOT control/manage it, they just used it (when space were free in the allocated accomodation, for people in their area seeking homes). The residents company had some well documented concerns about electrical issues in the tower, and general decision making processes when it came to improvements etc (which is common to Champlain). The effective inaction by the board of the residents association/company appeared to ignore these issues. Although these electrical issues were not the cause of the building being destroyed - they blighted residents.

- The building was not for housing "the Poor" (as you suggest), it was a mixed use property, some housing association and a considerable number of privately owned and sold dwellings, some I understand sold for as much as £400,000 (at the time), because of their premium location, and views. It's worth noting in the UK many builds have to contain "mix of affordable, low rent housing", as a condition of their being granted planning permission, and to increase available housing stock.

- It's relevant to note that in Kensington and Chelsea (if you've ever visited) and most of central London, Parking spaces are like "gold dust", space is at a premium and sold separately. In many parts of London, including new premium builds very few have parking, it's something you purchase separately, if you need it. Virtually all properties in the area of Grenfell rely upon on-street parking (I know because I visit the area frequently for work), or municipal high-rise parking garages - it's just the way things work in much of London (especially West London).

Other points concerning construction / yes - agree...

I think that the result of findings will determine the inaction by the residents association at Champlain over many decades - will be marked as being a significant reason for the known decay, and the structure being compromised sadly leading to the structural failure, which we're all discussing here.

One factor that does surprise me with Champlain - is how properties were bought and sold in the buildings, without there being any (apparent) legal obligation to advise a new purchaser of a "proposed" share of building improvement cost. (it's been reported, a new owner was surprised to find out a week after owning that they were going to be asked to pay their £80,000 share of improvements, with no prior knowledge).

 

[Retiredat46]

What were these two trunnion-like fixtures (one open, one closed) atop the columns used for?

At 1:26 in

https://www.youtube.com/watch?v=ElMjRSgMsiM&t=8s

I did a cursory look through the plans, but didn't see anything like that.

https://www.townofsurfsidefl.gov/do...-collins-ave-1979-plans.pdf?sfvrsn=bd2a1194_2

 

[DavPc]

These contain some slow motion and close-up views including the columns punching through the roof.

That, and Retiredat46's close-up of those columns once again leaves me disquieted in regards to the column-deck connections in this building. And it wasn't even just the roof deck - it appears several upper floors cleaved away cleanly from an entire row of the columns during the demolition.

If the articles stating this building's deck connections were not done to spec are accurate, then the folks in the North and East towers should insist on getting some X-Rays done on a random sampling of column-deck connections to make sure they don't have the same problem - despite both buildings appearing to be in OK shape.

 

[gonefishing2]

[URL unfurl="true"]https://res.cloudinary.com/engineering-com/image/upload/v1625506454/tips/S14A_of_14_elevator_section_penthouse_1979-plans_offrn3.pdf[/url]

Interesting Structural Elevator Elevation Revision for Penthouse Addition. Sheet 14A of 14 Structural, buried in the out of order PDF documents released by Surfside. Shows where C8 Anchor was attached to tie beam sitting on block infill for elevator shaft extension for penthouse. Shear wall stops at original roof level deck. So diagonal tear out appears to be CMU infill wall...

 

[gonefishing2]

[URL unfurl="true"]https://res.cloudinary.com/engineering-com/image/upload/v1625507044/tips/S12_of_14_before_penthouse_additionstructural-pages_hbeqyv.pdf[/url]

Original Elevator Shaft before Penthouse addition