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Partial collapse of 12 storey apartment building in Miami Beach:
Was built in 1981. Not much information as yet.
Building profile:
Was built in 1981. Not much information as yet.
Building profile:
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Miami Beach, Champlain Towers South apartment building collapse 151
- Thread starter bugbus
- Start date
If the design was inadequate, can the insurer's walk away? and, being condominiums, are the owners responsible for the repair costs? Some questions... Same questions for Millennium Towers in San Francisco.
Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?
-Dik
Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?
-Dik
JoelTXCive
Civil/Environmental
In Texas, to my knowledge; all design responsibility for the engineer and contractor ends at 10 years. They call it the Statute of Repose. I think even if you are grossly negligent you walk after the 10 years. I don't know if other states have that.
I see what you are saying. The insurers will say it was a bad design from day one, so how can they be responsible.
I see what you are saying. The insurers will say it was a bad design from day one, so how can they be responsible.
- Moderator
- #143
Retiredat46
Member
In many of the photos you see the same pattern of spalling on the underside of the floor slabs. It makes me think the rebar was just laid on the forms without chairs, and the rebar wasn't really imbedded in the concrete.
There was a building collapse further up the east coast of Florida long ago (early '70s?) where the chairs were too tall. The building pancaked during construction as an upper floor was being poured, killing several workers. As I recall, the incorrect height of the chairs was found to be a major factor in the failure, so proper placement of the rebar is obviously critical.
Would having the rebar too close to the bottom surface seriously weaken the slab? Or is this something that would show up after the failure that didn't contribute to the failure?
There was a building collapse further up the east coast of Florida long ago (early '70s?) where the chairs were too tall. The building pancaked during construction as an upper floor was being poured, killing several workers. As I recall, the incorrect height of the chairs was found to be a major factor in the failure, so proper placement of the rebar is obviously critical.
Would having the rebar too close to the bottom surface seriously weaken the slab? Or is this something that would show up after the failure that didn't contribute to the failure?
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Retiredat46 said:
That was probably Harbor Cay condominium. Collapse in 1981 - same vintage at this building. Whilst there were construction errors like rebar chair too shallow to the top rebar over columns, there were fundamental engineering design errors in that design.
On this building if you look at the roof level and the floor below that (11th or 12th), the rebar appears to have also unzipped like the photo posted at the ground level (photo above):
I think the bottom cover to the bottom rebar was very small - with possible badly consolidated concrete surrounding bottom of rebar and therefore little bond ==> hence ease of unzipping.
The potential unzipping of rebar may have commenced at a construction joint - the rebar was developed into the slab portion that collapsed, and as the slab/s fell it ripped/zipped the reduced-cover rebar in the span that remained. Notice how 'clean' the exposed slab edge at the roof level.
Also, notice the 3" vertical slices @ 10" c/c (?) to the dry-wall under the roof slab soffit - rebar 'cut' the top of the partition wall.
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The sudden collapse of relatively new RC concrete frame building is unusual. As the failure appears to be related to the crushing of
one or more concrete columns at the garage level the plausible reason is salt weathering of concrete. Concrete spalling due to the corrosion of rebars
should be also considered, but this will be rather unlikely, as the core of column shall be unaffected, and the local loss of section would create a "Freyssinet
hinge" contained by the vertical rebars and stirrups, or the remaining parts of these. The following is an interesting and likely related quote from a research paper
"Damage of Concrete and Reinforcement of Reinforced-Concrete Foundations Caused by Environmental Effects" published by Procedia Engineering as open access article:
"Salt weathering"
This occurs in concrete due to the capillary rise of water rich in slats through the soil and foundation structure. It
is prevalent in the areas with the considerable concentration of chlorides in the soil, ground water and atmosphere,
which is mostly the case in the coastal areas of the warm seas or in the structures where defrosting salt is often used
414 Zoran Bonić et al. / Procedia Engineering 117 ( 2015 ) 411 – 418
(road structures). Nevertheless, the mechanism of the crystallization process is similar to frost action. Namely, the
pressure caused by crystallization brings about the onset of cracks in the pore walls and afterwards the cracks, due to
crystallization in them grow bigger. This process, in presence of new amounts of water rich in salts, continues,
causing massive concrete degradation. The basis of this process is the reaction of calcium chloride (CaCl2) and
sodium chloride (NaCl) which causes changes in the Portland cement and causes generation of calcium hydroxide
(Ca(OH)2) [5].
This kind of concrete degradation, known also as chloride aggression, is particularly prominent in those cases
when the structures are positioned near the warm seas, in the conditions of high concentration of chlorides in the sea
water, soil and air. Warmer climate, in comparison to the areas with the continental and temperate continental
climate enhance salt weathering. In addition, high temperatures have an additional detrimental effect because
concretes, for the reasons of better workability are made with a high water/cement ratio which causes, in the
concrete hydration process, an increase in the concrete paste porosity, which facilitates capillary rise of chloride
saturated water after concrete hardening. The higher temperatures are the cause of the faster initial hydration of
cement which leads to the increased porosity of concrete and facilitates capillary rise and crystallization of chlorine
ions"
Full article is attached as pdf file.
one or more concrete columns at the garage level the plausible reason is salt weathering of concrete. Concrete spalling due to the corrosion of rebars
should be also considered, but this will be rather unlikely, as the core of column shall be unaffected, and the local loss of section would create a "Freyssinet
hinge" contained by the vertical rebars and stirrups, or the remaining parts of these. The following is an interesting and likely related quote from a research paper
"Damage of Concrete and Reinforcement of Reinforced-Concrete Foundations Caused by Environmental Effects" published by Procedia Engineering as open access article:
"Salt weathering"
This occurs in concrete due to the capillary rise of water rich in slats through the soil and foundation structure. It
is prevalent in the areas with the considerable concentration of chlorides in the soil, ground water and atmosphere,
which is mostly the case in the coastal areas of the warm seas or in the structures where defrosting salt is often used
414 Zoran Bonić et al. / Procedia Engineering 117 ( 2015 ) 411 – 418
(road structures). Nevertheless, the mechanism of the crystallization process is similar to frost action. Namely, the
pressure caused by crystallization brings about the onset of cracks in the pore walls and afterwards the cracks, due to
crystallization in them grow bigger. This process, in presence of new amounts of water rich in salts, continues,
causing massive concrete degradation. The basis of this process is the reaction of calcium chloride (CaCl2) and
sodium chloride (NaCl) which causes changes in the Portland cement and causes generation of calcium hydroxide
(Ca(OH)2) [5].
This kind of concrete degradation, known also as chloride aggression, is particularly prominent in those cases
when the structures are positioned near the warm seas, in the conditions of high concentration of chlorides in the sea
water, soil and air. Warmer climate, in comparison to the areas with the continental and temperate continental
climate enhance salt weathering. In addition, high temperatures have an additional detrimental effect because
concretes, for the reasons of better workability are made with a high water/cement ratio which causes, in the
concrete hydration process, an increase in the concrete paste porosity, which facilitates capillary rise of chloride
saturated water after concrete hardening. The higher temperatures are the cause of the faster initial hydration of
cement which leads to the increased porosity of concrete and facilitates capillary rise and crystallization of chlorine
ions"
Full article is attached as pdf file.
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- #150
8777 COLLINS AVE-1979 PLANS:
8777 COLLINS AVE - Structural Field Survey Report:
8777 COLLINS AVE - Unverified Inspection Report:
All Records:
8777 COLLINS AVE - Structural Field Survey Report:
8777 COLLINS AVE - Unverified Inspection Report:
All Records:
The reports go some way to suggest a lot of durability issues.
Not looked at the drawings yet but I suspect you'll find why that's the case....
Those bars ripping out of the underside of the slab is quite extraordinary, never ever seen that previously on any other structural collapse. Usually you see fractured bars not delamination areas like this. Very odd.
Not looked at the drawings yet but I suspect you'll find why that's the case....
Those bars ripping out of the underside of the slab is quite extraordinary, never ever seen that previously on any other structural collapse. Usually you see fractured bars not delamination areas like this. Very odd.
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Some of the most important drawings are conveniently missing - the piling plan, type of the piles used (looks like "Franki" piles), diameter, and the most important the location and exact composition
of the foundations - the beams listed suggest that some of the columns were supported by them, and that's adding to the list of potential mode of failure. It's also worth of noting that the level of the parking garage is below the sea level, so it's making the columns bases located in the "splash" zone and subject to accelerated corrosion and salt weathering of concrete. Unfortunately all of this is not a subject of 40 years' certification investigation, as the most important are the roofs and AC units.
of the foundations - the beams listed suggest that some of the columns were supported by them, and that's adding to the list of potential mode of failure. It's also worth of noting that the level of the parking garage is below the sea level, so it's making the columns bases located in the "splash" zone and subject to accelerated corrosion and salt weathering of concrete. Unfortunately all of this is not a subject of 40 years' certification investigation, as the most important are the roofs and AC units.
8" thick RC flat plate to typical floors.
9.5" thick RC flat plate at ground floor.
EDIT:No obvious column transfer conditions to the ground floor level See post below.
Typical floor dimensions and column layout to the collapsed area:
Basement dimensions and column layout to the collapsed area:
Very 'light' on structural walls for lateral in E-W direction!
3,000 psi concrete from Level 9 floor to roof level - oh, the 80's!!!
9.5" thick RC flat plate at ground floor.
EDIT:
Typical floor dimensions and column layout to the collapsed area:
Basement dimensions and column layout to the collapsed area:
Very 'light' on structural walls for lateral in E-W direction!
3,000 psi concrete from Level 9 floor to roof level - oh, the 80's!!!
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AUGUSTACOURTER
Structural
Something that wasn't obvious to me before. The entire site's at-grade slab was elevated, and a large portion collapsed, essentially all the way to the pool and to the property line, even though the collapse of the tower was 100' or so away from this extent of the pool deck. It is remarkable that the remaining building didn't collapse as the elevated slab supporting the parking of the cars in the images failed and dropped a level, leaving the still standing columns with an unbraced height which is double of the "design" condition.
Champlain Towers Town of Surfside Public Record LINK...
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