: Most standard buildings can be modeled as repeating 2D frames, but complex or multi-storey structures often require 3D modeling to capture lateral load distribution and global stability. Member Alignment
For slender steel members, ensure that second-order effects (P-Δ and P-δ) are activated. A model without large-displacement analysis will grossly underestimate sway moments in tall steel frames. modelling of steel structures for computer analysis
Steel members are never perfectly straight. The AISC Code of Standard Practice allows for an out-of-straightness of L/1000. In buckling analysis, this matters. : Most standard buildings can be modeled as