Vancouver House (1400 Howe St) | 151.5m | 52Fl | Completed - Page 45

Otis_Van · #**881** Posted **Apr 24, 2016, 6:06 PM**

Looking again, it seems like they may have repositioned it. The green arrow is pointing to a new support that wasn't there before. It has a yellow line tied around it, and if you look at McMinsen's other pics, you can see that entire rebar structure laying on the ground, just prior to being hoisted into place with the line (I think you can see a couple of men working on it).

Is it possible to a make a mistake this big? Or would they have reconsidered the positioning after the fact? Seems odd either way.

axestone · #**882** Posted **Apr 24, 2016, 7:56 PM**

Damn Mcminsen, you sure do take amazing excavation photos.

mcminsen · #**883** Posted **Apr 24, 2016, 9:40 PM**

Quote:

Originally Posted by Otis_Van

I noticed earlier today when I walked by that they seemed to be breaking up a section of concrete near the centre of the core.

Just went back and compared McMinsen's photo from a week ago with one from today, and it looks like they took out one of the big support columns.

Would be curious to know the story.

Before:

After:

Here's a sequence of close ups with dates.

March 8 '16, my pic

March 14 '16, my pic

March 19 '16, my pic

March 20 '16, my pic

March 30 '16, my pic

April 8 '16, my pic

April 11 '16, my pic

April 22 '16, my pic

cairnstone · #**884** Posted **Apr 25, 2016, 2:11 AM**

interesting catch. Could be a number of reasons from usage change to outright mistake. Its not unusual to remove concrete and replace it. Was on one project after a column was poured 2 levels they went back and demoed it. As i recall they tied the column steel wrong or it was changed. Some times the engineering is done on the fly.

mcminsen · #**885** Posted **Apr 25, 2016, 3:37 AM**

I'm thinking there may not be any design flaw at all but just a construction flaw. Inspection may have found something that was not absolutely perfect and it necessitated a redo. We'll see if they actually rebuild it like it was before.

mcminsen · #**886** Posted **Apr 25, 2016, 4:05 AM**

Quote:

Originally Posted by Otis_Van

Looking again, it seems like they may have repositioned it. The green arrow is pointing to a new support that wasn't there before. It has a yellow line tied around it, and if you look at McMinsen's other pics, you can see that entire rebar structure laying on the ground, just prior to being hoisted into place with the line (I think you can see a couple of men working on it).

Is it possible to a make a mistake this big? Or would they have reconsidered the positioning after the fact? Seems odd either way.

I think the angle of the pic with the green arrow is deceptive. It looks upright but it's not. Here's a better closeup taken about one minute later showing it laying on the ground.

My guess is that it will just be rebuilt like the old one in the same place.

April 22 '16, my pic

mcminsen · #**887** Posted **Apr 26, 2016, 8:35 AM**

Forms are up for what looks like a remade pillar in the same place.

April 25 '16, my pics

cairnstone · #**888** Posted **Apr 28, 2016, 6:37 PM**

they installed the wrong zone. the first pour they had double lift steel. in the new pictures you see only enough rebar for splicing the next lift

SFUVancouver · #**889** Posted **Apr 28, 2016, 11:46 PM**

^ Interesting observation. What does that mean, exactly?

officedweller · #**890** Posted **Apr 29, 2016, 2:52 AM**

Looking at the old pic, the first installation had rebar 2 storeys high (double lift?).
The new rebar is only one storey high (single lift?).

I'm guessing that 2 single lifts (2 single storey rebar cages stacked on each other) is structurally stronger than one 2 storey rebar cage.
Is that right?

Marshal · #**891** Posted **Apr 29, 2016, 9:56 AM**

Quote:

Originally Posted by officedweller

Looking at the old pic, the first installation had rebar 2 storeys high (double lift?).
The new rebar is only one storey high (single lift?).

I'm guessing that 2 single lifts (2 single storey rebar cages stacked on each other) is structurally stronger than one 2 storey rebar cage.
Is that right?

No.

Structural strength depends on the size of the steel and the design/geometry of its placement, along with concrete coverage.
Issues that might explain the difference: the column may just end there, the tie in pattern regarding the slab requires it, simple constructability (easier to put together), if there was a mistake, they may simply be using what's available - shorter lengths, and so must build one floor at a time (as opposed to breaking the scheduling path and waiting for longer rod) . . . i doubt it, but I have given the OK for such changes in some circumstances.

officedweller · #**892** Posted **Apr 29, 2016, 10:20 AM**

Thanks.
What does "double lift" and "single/next lift" mean?

cairnstone · #**893** Posted **May 7, 2016, 3:20 PM**

Quote:

Originally Posted by officedweller

Thanks.
What does "double lift" and "single/next lift" mean?

repair columns are typically staggered and in height between pours. This way you are only placing the rebar every other pour. example is if floor height is 8 feet the rebar will be 16 feet roughly and every other column gets set. Saves crain time and uses way less steel as you remove 1 splice section.