I am designing a structure with steel truss supported by concrete columns, performing the analysis and design, I already have the right sections for every members. And since I am designing now the connection (truss-concrete column), I needed to delete the concrete and retained the truss and added pinned supports just to get the reactions in the truss support. However, when I ran again the analysis and design, I noticed the utilization ratio of most members of my truss became lower as when it was combined with concrete structure. Which is correct way of designing this, design the two separately or in combination?
Hello,When we model any structure, we tend to get the actual site representation in our model. But the boundary conditions play a vital role here. When you model the steel and concrete separately you use fixed or pinned supports most of the case. But when we consider both in a single model the interface of the steel and concrete may not be ideal fix or ideal pin. So, depending on that there will be some changes. Also, the overall stiffness, displacement pattern and load distribution play a significant role in these cases. However, I have seen users using both the approaches in their projects and I think there will be not much deviation in the end results. Are you seeing a huge difference? Can you point out the areas where you are getting differences mostly?