Steel horizontal diaphragm at roof level of a Reinforced Concrete Building?

[brTCP]

Hi, I am designing a reinforced concrete building with a steel flat roof. From my calculations, it seems beneficial for this building to have a diaphragm at roof level, but here is the question: is it feasible to design a steel roof as a diaphragm? Usually, due to temperature or other factors, I use a statically determinate roof, but having it work as a diaphragm requires fixed supports (I would assume). What are your thoughts on this? Is this common? Is this a good idea?

 

[HDStructural]

There are things to consider with thermal expansion at the roof level, but that can typically be ignored depending on building size and use, especially if the building isn't extra large and is insulated with roof insulation over the roof structure.

You can have steel beams designed as pinned ends connecting into concrete walls. You can detail this with horizontal short slotted holes at the shear connections. Think about a typical tiltup warehouse, precast concrete exterior walls with steel joists and metal deck for the roof system.

I don't think it is an issue although I don't know the size or use of the building you are designing.

 

[brTCP]

HDStructural, I am not sure if I explained the issue clearly. What you are describing is the common use case. I am wondering about the seismic behavior of this building (under lateral loads). Is it common to design the steel roof as a diaphragm to distribute the horizontal loads to the vertical elements?

 

[HTURKAK]

You did not provide a lot of info . here.. There are hybrid systems the frames are composed of RC columns and steel trusses or beams . How ever , the roof for these systems in general is not designed as a diaphragm.
Probably it would be better to design with flexible diaphragm assumption.

Pls provide more info . to get better responds.

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He is like a man building a house, who dug deep and laid the foundation on the rock. And when the flood arose, the stream beat vehemently against that house, and could not shake it, for it was founded on the rock..

Luke 6:48