Structure OS — Controls
DRAGorbit camera
WHEELzoom
RIGHT-DRAG / SHIFTpan target
SPACEplay / pause mode animation (auto-orbit in static)
1 – 6animate mode shape 1–6 at true frequency ratios
0 / ESCreturn to static results
Lcycle load case
Dtoggle deformed shape
S / G / Fstress map / ghost frame / load vectors
+ / −deformation scale
Aauto orbit
Rreset camera
Elastic first-order analysis · 3D Euler–Bernoulli beam elements (12 DOF) · banded Cholesky LLᵀ ·
lumped-mass inverse-iteration eigensolver · ASCE-style equivalent lateral force with computed T₁ ·
W14×90 columns / W18×50 girders, A992 steel. P-Δ, connections and member buckling out of scope.