Precast Panel to Panel Dowel Connection 1

[dis_]

I have seen single layer dowels been used between panel to panel vertically most of the time despite the fact that there are two layers of reinforcement in panel and am wondering why is the reason for this? Can we use two layers of dowel bars for 200mm thick wall instead of is it not practical on site?
And if ligatures are required for panels, how do you take buckling of dowel bars into consideration since it they have no ligatures?

 

[Agent666]

If you confine the outermost layers, dowels through the middle are also confined. The dowels are an offset lap with the vertical steel in the panel. In most codes depending on ductility, you may be required to provide confinement for wall laps.

The main reason is for thin panels you simply cannot get two layers of dowels as you need a reasonable tolerance.

I'd say in a 200 panel having two layers of dowels into grouted tubes is too tight. Sketch it out to scale.... or work it out

Lets say 30mm cover each face, 12's horizontally, 16's vertically (while you can nest the ducts into the same space as vertical bars lets ignore that for now). Therefore, room left is 200-2*30-2*12-2*16 = 84mm clear.

Say for 16's vertically you want a 25 diameter bar, so probably 60-70 diameter duct.... obviously cannot fit two of these across the thickness if ~85mm clear core of panel.

 

[dis_]

Thank you Agent.
If so, why do we need to confine the internal bars in columns considering we have outmost closed ligature already?

 

[Agent666]

By confining outermost layers, I mean links or stirrups between the 2 outermost layers in a wall.

In a column a single stirrup around the perimeter does not confine concrete at intermediate bars locations. Put another link at the midpoint in the following picture and the zone of unconfined concrete reduces. For a wall you need regularly spaced cross ties along the length to achieve the same effect.

 

[dis_]

Thank you very much

 

[dis_]

I come up with one more question in regards to singly dowel bars. Won't it reduce my out of plane bending capacity or does that mean I have to make the panel to be pin in the weak axis in my model for analysis since singly dowel bars are used here? (panel to be connected at floor level) I have relative short panel - 200mm x 800mm

 

[Agent666]

I guess you need to take into account any out of plane effects for your given scenario.

Typically you'd make the panel connection close to floor level, and for a building you might be reducing the stiffness out of plane anyway so the panels don't participate in taking loads away from the orthogonal lateral system. Because in reality they will crack and possibly yield out of plane to accommodate/maintain drift compatibility with the orthogonal lateral load resisting system. So they might more or less reach a pinned state at some point in the loading cycle.