Panel Friction

[ljk80oze]

Hi

I have done very little precast design and I am designing some precast shear walls with large axial loads. The panels sit on a continuous grout bed and have steels dowels at each end.
What would be reasonable value to use for a coefficient of friction for ultimate loading? Can i also use the shear capacity of the dowels at the same time?
A value of 0.3 has been used for inital calculations but i would like to get some feedback on industry standards.

Many Thanks!

ljk

 

[JAE]

Normally you don't ever consider friction for lateral resistance in building design - except for soil friction at the base of footings.

You should use the dowel shear strength - possibly using Shear Friction provisions of ACI 318 (chapter 11) - or its Appendix D.

 

[ljk80oze]

Thanks for you reply.

It seems pretty conservative to ignore friction when you have large axial loads and contact area. If a conservative value of the dead load is used in the calculation why should this force be ignored? Is there empirical evidence to suggest this shouldn't be used or are you reffering to specific code restricitons (i am in Australia).

Thanks again.

 

[UcfSE]

Friction is unreliable, and net normal force may vary. A lot has to do with construction practices. What happens if there's some sand under the panels, for instance? Given the number of things that could go wrong, I would say we don't normally use friction; it's just too unreliable. If you can find the appropriate data and your code doesn't restrict it, and you can still sleep at night, I suppose it's ok.

 

[JAE]

There is also wind uplift and seismic vertical forces that may cause the panels to jump and therefore friction, as UcfSE suggests, is unreliable. I wouldn't count on it.