Seismic R Value if column for two mterials

[FRACH23]

I was quite confused how to deal with the R value for my roofed footbridge. I have a cantilevered concrete column and had my flooring and roof frame by structural steel. I assume the upper part being steel has different seismic response than than the supporting concrete column. Do i need to use two mathematical models when i wish get my seismic forces each material part?

 

[KootK]

In this case, I would base your R value on the concrete columns as they will dominate the seismic response.

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.

 

[FRACH23]

Thanks a lot KootK