huangyhg

cracks in the area of inserts.
columns have been already situated on building place. columns have got three inserts along those lenght. on columns, in the area od inserts i noticed cracks, which was shown in enclosed pictures.
the question is - is this type of cracks a result of thermal action (in steel and concrete) from sunny weather?
is that a void showing at the lower front corner of the insert?
do you have more photos? it does appear to be the type of cracking that you would expect from thermal effects, but i would have expected this to happen with a drop in temperature, not a rise. if i read this correctly, i'm guessing you have a strut trapped between two columns, right?
if this is the case, the metal strut will rise to a higher temperature than the concrete, and expand linearly and push upon the column. those forces must be tremendously high before they will cause a crack. conversely, if the temperatures drop and the metal shrinks away, you can get a crack at fairly low changes in length.
you say you are wondering about sunny days; i would wonder about cold nights! how much play (ie: space) is present between the angle and strut at the connection? how long is the strut?
more photos, more information, please. an overall shot would be very useful! hopefully someone can help you out...
cheers,
ys
b.eng (carleton)
working in new zealand, thinking of my snow covered home...
from the horizontal crack, it looks like a patch and sack location to cover up a rock pocket in the coloumn pour, in which case the cracks would be due to local shrinkage of the patch. the hypothetical rock pocket could have been caused by a high concentration of rebar and insert steel in the area making placement difficult without good vibrating measures.
any construction history on the location?
what steel is in the column and insert?
how thick is the panel?
mike mccann
mmc engineering
hi katep
looking at the picture there could be a number of reasons like the rusting steel behind the concrete flaking.
have a look at this link i realise its not reinforced concrete as such but it may give you some idea as to what happens when steel and concrete are in close contact
an insert at the edge of the column with not much concrete to protect the insert from the elements. the insert is rusting all along the edge of the column and thus cracked or peeled that weeks concrete bit. this is malpractice.
the insert is better at the center of the column and the weld could extend to the the face of the column to get the horizantal element to bolt with it.
i suppose that it's has been coused by thermal effect, becouse all columns, where we could find this type of defections are directed on the south.
i will be enought if we repair it using repair-mass for concrete/ epoxy injection?
ad) msquared48
any construction history on the location? it was assembled 6 mounths ago.
what steel is in the column and insert? b 500 sp, fi 12-25
how thick is the panel? 12 mm (i mean thick of insert)
1. insert with no effective corrosion protection system.
2. plate set directly adjacent to corner chamfer, so the corner comes off easily.
3. because of easy entry of water around the plate, corrosion initiates at sides and probably under plate, spalling results.
thermal? i doubt it. corrosion is the problem. ferrous oxide occupies much more volume than steel.
i agree with the posts above that say corrosion is playing a major part.
i suggest you look into doing some proper repairs of this e.g. removing rust adding a corrosioon inhibitor and a bonding agent, then covering with non porous repair grout and a sealer
doing it incorrectly will not last long
hokie nailed this one. the first two are at firm ground. also note both the angle and the embedded plate have started to form rust that indicates humid environment, which has its share on the failing. better ventilation may be required on top of structural repairs. or, use all galvanized steels.
futher exam the photo, confirms hokie's third point is valid as well - evident by the brownish water marks below the plate. again, the source could be caused by condensation on humid air.

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