Hi Mogi - I think its overly complex and the actual purpose of the concrete is not apparent. Why don't you model it and find out how much the concrete helps? Plus model a concrete high rail design of same dimensions and compare. They just need to be simple models to give you an idea. This is called a trade study or trade off study. I'm sure if you bond the steel to the concrete it will help, my concern is that it won't be bonded but be mechanically locked in place via the 40 bolts. Then it becomes uncoupled from the structure over time. LMs move to EG is a concern in this respect. There's always some backstory to this sort of change that they will not discuss. Otherwise they would have gone to a high flow concrete which is cheaper then EG. Peter

Mixed media structures are complex and often done for various reasons that don't work out. I'd stay in one environment.

https://en.wikipedia.org/wiki/Trade_study