Precast sandwich panels: composite design during lifting/handling

[Thedg]

I'm designing precast prestressed sandwich panels with carbon fiber wythe connectors such that the panels will behave as "partially composite." The few design examples I have found determine the level of composite action based on the in-service condition (simple span) and corresponding shear span (1/2 span), but then use that level of composite action when analyzing the lifting and handling cases, even though the shear spans during lifting and handling are much lower. When I check a typical panel for my project, often the overall (in-service) condition will have capacity based on the overall level of composite action, but locally during lifting the section is overstressed due to the lower level of composite action. When checking the lifting and handling cases with the composite level of the in-service condition, the panel has capacity.
Anyone have any insight into this?

 

[KootK]

Anyone have any insight into this?

You're not likely to find my insight very satisfying but I'll give it a go any: I agree with you 100%. I suspect that you may have identified a legitimate issue with current practice.

I don't know much about carbon fiber wythe connectors. Is it safe to assume that, were they to fail, they could not be expected to fail in a ductile fashion?

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[Thedg]

Thanks KootK - I appreciate the input. Since it does seem to be "standard practice", I was hoping to find an alternate load path or theory that justifies this approach, being that it does seem to perform adequately.
And yes, I think failure of the carbon fiber wythe connector (or more likely the embedment) would not be a ductile failure.