Tilt Up Wall Deflection

[emart0429]

I'm looking for any information someone may have on determining the deflection, and more importantly the stiffness of a tilt up wall panel for an in-plane shear load. I'm currently working on a structure w/ 9" thick exterior, tilt-up, special reinforced concrete panels, and numerous interior special steel moment frames. I'm performing a lateral analysis of the structure, and am trying to determine how much of the seismic load ends up in the frames, and how much ends up in the walls. A typical individual wall panel is approximately 21' long and 30' tall, with numerous panels making up wall lines in the 42' to 300' range.
I've got a copy of the PCI manual which has info on the stiffness of the wall based on cantilever action. But, what I'm really wondering about is the composite action of the walls. How would one account for the connection of the panel to the foundation, and the individual connections from wall to wall.
Any and all information would be greatly appreciated.

Thanks,

Erik

 

[hokie66]

If you don't have to connect the panels together to achieve adequate stiffness, it is best not to do so. The edges and corners are vulnerable to tensile failure. As for contribution of the footings, generally it just depends on the capacity of the connections between wall and footing.

 

[csd72]

emart,

I think you are overanalysing this one. Look at the cantilevered panels individually and I am sure you will find that they are much much stiffer than the portal frame.

The distribution of load will largely depend on the diaphragm and will only really depend on the stiffness of the walls/portal frames if the diaphragm is rigid.

Getting composite action out of all the panels is difficult and (as hokie66 stated)can cause more problems than it is worth.

Think of the simplest possible option, and if it works then leave it that way. Only add complexity when the simple solution doesnt work.

csd

 

[emart0429]

hokie66 and csd72, thanks for the advice. So, now I'm onto my next problem. I'm trying to put together hand calcs to verify a model developed by another engineer, and in the model, the force distribution is obviously somewhere between rigid and flexible diaphragm action. What I've got is a two story square building approx 300'(EastWest) x 360' (NorthSouth). The roof diaph is 1.5B20 decking over bar joists, the floor diaph is 1.5VL20 decking w/ concrete topping to 4" total thickness over bar joists. The problem is that there is a 60' wide (EW) by 220' long (NS) opening in the middle of the diaphragms. So, for wind/seismic in the NS direction, I've essentially got 2 separate diaphragms that are 120' wide (EW) by 220' long with the tilt-up walls along the outside edge and the moment frames on the inside edge. Based on my hand calcs, the roof diaph would be a flexible diaph, and the floor would be a rigid diaph (per ASCE 7-02 9.5.2.3.1). However, if I run w/ those numbers, I get a lot more roof load into the moment frames, and a lot more floor load into the walls than what the model calculated. Is there any way using hand calcs that I will be able to match the model?

Thanks in advance,

Erik