5:38 looks like point loading and deflection failure... Notice the lowered triangular shapes, they incline /depress at the four corners... Looks like lack of or loss of load bearing capacity with respect to the applied load at that location... Notice the "45" degree breaks... U know loads love to resolve in 45 degrees... Take care...
@CornellEngineers
2 жыл бұрын
Thanks for the comment and suggestion. I have thought carefully about whether I agree with your suggestion and how an engineer would prove or disprove the bearing failure assertion. I think coring or drilling the concrete would show whether there was a void at the underside of the concrete at that very spot. Loss of soil and therefore support could occur from pumping of fines (pavementinteractive.org/reference-desk/pavement-management/pavement-distresses/water-bleeding-and-pumping/) through the control joint but I think that is less likely in sawn joints which are not right through the concrete. That leaves shrinkage/curing issues. This website discusses slab curling from uneven drying of the concrete www.woc360.com/concrete-masonry-resources/preventing-and-repairing-slab-cracks-part-2 This is similar to what you are suggesting but upside-down if you like. The slab corners pop up due to drying strains and then are broken off by loading. This sort of curling is known to happen in suspended slabs that are supported on 4 walls but for suspended slabs we design suspended slabs to be tied down at corners and provide reinforcement continuity to minimize cracking. Any one else got some ideas?
@ForensicCats
2 жыл бұрын
@@CornellEngineers , give me a little to digest your data and I will reply again... Fyi, I have been able to duplicate curling by heating the soil at one location (a joint) and then placing a sample of concrete over the "four corners"... Simple answer, an an obvious bone if you think about it... The heated soil wicks the water from the concrete OR it "boils it to the surface as bleed water"... With all that said, soil temperature should be the same or you will get differential drying and perhaps this will explain a lot of our concrete issues that just seem "inexplicable"... Core drilling is always an excellent choice for gathering data, I simple use a probe and it has a pressure guage... I will attempt to find that probe video and I hope to sell u on the exploratory idea of it's usage... Now I will open ur links and learn...brb with my thoughts and I hope I agree (my bias, I want you to be correct)...
@ForensicCats
2 жыл бұрын
@@CornellEngineers , Cornell Engineers, I hope you saw my previous reply and I read the two supplied articles you provided... I enjoyed the water bleeding up images with the asphalt... I am of the belief that no crack is random and just because we cannot determine the stress that caused it does not make it ''random'' as ACI states, "Completely crack-free slabs are unrealistic in most cases. ACI 302.1 recommends that the contractor advise every owner “that it is completely normal to expect some amount of cracking and curling.”... I believe all cracks have an explanation and it could simple be that the aggregate created a ''weak plane'' in the concrete... Imagine if you will, stone connecting / contacting each other in the slab, this would create an ''underlying control joint''' as the paste around those stones would not be uniformity covered... I have experimented with this theory with butting stone together and adding concrete around my ''control joint of stone'' and with predictable results, the sample fractured as the ''design stone layout"... Cornell Engineers, I am in youtube's timeout at this time, for one week (because I did a covid video = shame on me, ha) but, I want to load up a video where I am standing on a thin piece of glass and because no deflect of the subsurface (based on my loading), the glass does not fracture... Basically, I find a few failures in non-reinforced concrete, deflection (soil reduction values) and overloading (surging the concrete with vehicle traffic and their continued sudden stops at the same location)... think of the ruts we see at intersections, how the asphalt will show those deep ruts and the same where cracks in concrete is shown... Reinforced concrete is a different animal and I reference that as a marriage of steel (man) and concrete (woman) and water is the ''character'' that will break up the marriage... The ''man'' surfers from rust jacking and the woman from salts / efflorescence failure. Here is an old video I put up on this kzitem.info/news/bejne/mW1vl4uriJZhg6Q (one of my other channels)... You might like what I have planned, a lot of rebar pullout test and explanation on the importance of a rebar pullout test... I hope we can collaborate in the future... Perhaps, on the Marine Towers West Garage Collapse; I am getting a lot of data from the owners of the East structure and engineer reports (one of which, instructs the maintenance man to do structural repairs and also it lacks a shoring detail or even a request to hire a shoring expert)...
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