Repeated pattern of symmetric concretecracks from both sides of a column from 3rd floor and upwards.

[ednar]

The picture shows the building under construction, it was November 2011.

October, 2012 there was no noticeable cracks.

October 2013 there is significant random patch work and cracking of hollow block segments.

But one column on the opposite side there is a column with different kind of cracks, each floor starting 3rd floor there is symmetric pattern of cracking like a Christmas tree from left and right of the column directed upwards, starting approximately from the joint of the slab and the column.

I didn't take the picture of the cracks, I may get it later. Must those cracks will be structural (since the pattern repeats symmetrically on every floor starting 3rd, but there are no cracks noticeable on the slab of the ground floor). Or it might be just hollow block wall innocuous concrete cracking only?

The under construction picture may give the idea what kind of technique they used and what caused so many cracks in the hollow block sections and maybe the repeated pattern cracks around the column. I'll try to get more information if needed.

 

[ednar]

I mean I didn't notice cracks on the slab on the top of the ground floor.
Sorry for the orthographic errors, I didn't know there is no edit option.
The building is in an earthquake prone zone.

 

[Ron]

Repeating pattern cracks in concrete usually have meaning, ranging from innocuous shrinkage to structural issues. Your description would lead me to look at stirrup cover issues or spacing issues.

 

[JAE]

Post some photos of the actual cracks, please.

 

[hokie66]

Transverse cracks in perimeter columns are commonly flexural cracks due to shortening of the floors. Not sure if that applies to your situation, as the "Christmas tree" cracking doesn't sound typical. Where is the cracking located in that long building? Are there effective movement joints?

 

[ednar]

I may not go there for some time (a month or two), but I have rather a good idea. When I'll be there I'll take a photo.

I've attached a picture. I found a photo of the building under construction (just the opposite side with the opposite column visible) and the plan where the columns were marked as well. I marked the cracks location on the photo of the affected side from both sides of the column with red dashes.

I only don't remember whether the cracks' curvavure is convex or concave. You can see on the plan right to left until this column the building is symmetric, from bottom up it is the same design 4th-10th floor and something different beneath (commercial area), so cracks start above the 4th floor.

As far as I remember there were no reported earthquakes in the area during the one year period when the cracks has developed. The under construction picture is from about 2 years ago - likely November 2011 and it is all I have as to construction details. The building had been completed around February 2012.

It may be something superficial or likely a structural (serious) problem? If the latter what is usually the solution?

 

[hokie66]

I must have misunderstood, as I thought the cracks were in the concrete columns. So are these cracks just in hollow block upstands? Hollow block is very brittle, and doesn't take much movement at all before it cracks. Seems like a poor solution for perimeter upstands, especially in a seismic area. Depending on how you define "structural", it may not be an issue for the building as a whole, but the facade falling off in an earthquake could be serious.

 

[ednar]

I'll take a picture when I'm there, maybe it is just the hollow block upstands.

Also significant visible cracking at the hollow block wall like structure on the top of the building (marked red) in additon to random cracking in other upstands which is being patched when happens (not correlated around a column with the same pattern on different floors like that one).

Why all that wasn't visible 9 months after building completion, but it is prominent now after 21 months?

The bare concrete structure may move cracking hollow block sections because they are rigid? Under what forces? Temperature or ground movements? I saw even high rise buildings sometimes also using hollow blocks no such visible cracking.

 

[ednar]

Might be also ground settling or like that, I have a house built in the similar way, there were cracks in hollow block walls, the cracks stabilized after about 2 years, but they also weren't larger than 1-2mm inside and outside in finishing maybe only 0.5mm max. And visible cracks mostly from the top of door or windows towards the ceiling (and I know it could be avoided by adding small beams). But the house was amateurish, I thought in professionally built structures it shouldn't happen, maybe the higher the building the larger the movement.

 

[jayrod12]

If the masonry was installed too quickly after the concrete was poured it could be a case of concrete creep causing unacceptable deflections for masonry. But I haven't even looked at the pictures I'm just going off of my hunch from reading everyone else's comments.

 

[hokie66]

Using hollow unreinforced block for that parapet indicates negligence in the design and/or construction. A disaster waiting to happen.

 

[ednar]

The parapet appears to have columns placed every 3 meters (the thickness looks around the same as the height of hollow block - 20cm then), but no beam on the top. Usually horizontal and vertical thin rebars are added for reinforcement, if it is what is meant by reinforcement.

I'll get some pictures later, I could try to pass there by the end of November, what mostly alarmed me - the regular pattern cracks on every floor symmetrical from both sides on the column after I found an article stating that "Other warning signs are ... repetition of cracking at the same locations on each floor."

 

[ednar]

here are the pictures. what it might mean?

 

[BAretired]

Looks like deflection of the structure, at least on the first two photos. The infill wall is rotating counterclockwise but not releasing from the column except at the diagonal crack on top.

BA

 

[Ron]

Those cracks in the last photos are stucco cracks, not structural cracks. Looks like stucco might be starting to fall off the walls in a few areas. Based on the earlier photos, the stucco was likely direct applied in some areas and on sheathing in others with no isolation of dissimilar materials.

 

[hokie66]

Agree with both BA and Ron. The first three photos look like they could reflect cracking of the substrate, but the last three are cracks in the finish material. It would be interesting to know what material was used, but I doubt it was a recognized proprietary product.

 

[ednar]

Yes, the first three pictures it is what I meant.

As to the topmost floor it looks like the same pattern was present, there is a painted patch job (encircled yellow), there is other patch work visible on the building, so it is likely the topmost floor is where it appeared first and then it propagated downwards, the later cracks have not been patched yet, but then the question why the crack on the topmost floor didn't expand or the patch material may be flexible?

The adjoining column surface (encircled red) also has a (different) repeated crack pattern which doesn't present on the column to the left of it (encircled green), it might be connected to the same (could be) deflection?

 

[hokie66]

The face of the column denoted in green is offset on at least one side, while the one denoted in red is more or less planar on both sides. Whether or not that makes the difference, I don't know.

 

[Ron]

I'm still not convinced the cracks are substrate cracks. The offset in the green box could easily be stucco delamination. All of the major cracked areas appear to be masonry infill.

 

[hokie66]

Oh, I think there is definitely an offset there, but agree that this could all be shrinkage and/or delamination in the plaster.