reinforcement: column-beam or wall-slap

[BauTomTom]

Hi Struct.Eng's

There are three different or maybe even more possibilitys how to connect the beam reinforcment to a edge column or the slab reinforcment to the concrete retaining wall.

Have a look on the attached sketch. Me personal I like the left solution because it is easy to manage on site. The column or wall can be concreted to the top and then later the connection reinforcement "U bar" will be placed.

BUT: Is this type of detail not weaker then the middle one or the right one? Does it not give a better connection if the L-bars are casted INTO the column or wall?

Bau Tom Tom

 

[HeavyCivil]

I would doubt that the U bar is developed on the left detail.

With two layers of bar I would do something like this: (diagonals are optional - this was a tall tank wall)

 

[csd72]

I believe that those U bars are frowned upon in some conditions as they have both the compression and the tension of the bending moment pushing along the same direction of the bar.

 

[BauTomTom]

oouu so much negative comments on it? I thought it would be quite a common detail.

Of course it is a detail which does not transfer moments. Is actually a kind of a pinned support

Bau Tom Tom

 

[ishvaaag]

Here (Spain) the practice of the left detail is common for splices with building 2nd level and lower basement walls; in fact there are propietariy systems where the projecting (slim) rebars are hidden whilst concreting in a C-like cold formed shape within the rebar cover space, then straightened to cast the slab at the level. As BauTomTom says, it is usual to assume these connections hinged.

 

[hokie66]

I see nothing wrong with the U-bars. As ishvaaag says, this is a common detail at slipformed cores, with proprietary systems like "Rebox" being the norm. If anything, the U-bars may develop too much moment for the assumption of a hinged joint. They have been shown by testing (Nilsson and others) to be more efficient in moment development than the type joint shown by VTEIT above.

However, there is generally no reason for the 90 degree cogs to go below the construction joint. Either lean them over or use 180 degree hooks within the slab or beam depth.

 

[BauTomTom]

So you guys also use the U-bars at the intersection Retainingwall and slab?

Ok by beams and columns maybe it is better rather to go for the 90degrees L' shape bars which are cast into the column

Now I found even some reports in the internet with even more solutions uuhh now am even more confuse what is the best, easiest and strongest connection

BauTomTom

 

[ishvaaag]

Yes, I have used the detail in basements. Respect getting "confused" don't worry, you are becoming wiser, whilst appraising the extent of the issues that may influence a detail being preferable to another.

 

[hokie66]

If this is not a moment connection, and most end panel connections are not, full development is not required, particularly of the bottom bars. I would never require top slab or beam bars to be cast with a wall or column below. Will just result in your being laughed at.