How to Analyze Steel Frame with knee braces CISC

[SteelMind]

Recent grad structural engineer and I need to conduct an analysis on a steel platform structure using CISC standards. For column design, I was told I need to analyze compressive strength and the beam-column strenght of the columns since they have knee braces. Problem is I dont know where to start. Do the knee braces just cause the steel frame to become a moment resisting frame and I analyze it as such? The frame has the weight of the structure and lateral load from seismic. How do i even start?

 

[KootK]

Do the knee braces just cause the steel frame to become a moment resisting frame and I analyze it as such?

That's the gist of it. Good instinct.

 

[SteelMind]

That's the gist of it. Good instinct.

Hey, thanks for responding. So would I start off by solving for the reaction forces on the frame (I guess I would have to assume two pinned connections and analyze it as an indeterminate structure) and then use method of sections to determine the loads in the each member including the knee braces?

 

[SteelMind]

View attachment IMG_7596.jpeg

 

[KootK]

So would I start off by solving for the reaction forces on the frame (I guess I would have to assume two pinned connections and analyze it as an indeterminate structure) and then use method of sections to determine the loads in the each member including the knee braces?

Yessir, if you're doing this by hand rather than using an FEM modelling program. You might assume an inflection point at the middle of the beam under lateral loads to simplify things.

 

[SteelMind]

Yessir, if you're doing this by hand rather than using an FEM modelling program. You might assume an inflection point at the middle of the beam under lateral loads to simplify things.

Thanks! I'll give it a go.

 

[ANE91]

Good ol’ portal frame method! Good until the building gets tall.