Watch an OpenSeesPy time-history analysis of a 3D steel frame respond to the 1940 El Centro earthquake, animated in 3D.
Skeleton + facade animation • Synced displacement/velocity/acceleration • Amplification slider
Explore the fundamental behavior of single-degree-of-freedom systems undergoing free vibration without damping.
Interactive mass-spring system • Real-time parameter adjustment • Time history analysis
Explore the effects of viscous damping on free vibration response with interactive comparisons.
Critical damping • Overdamped response • Underdamped oscillations • Envelope decay
Free-vibration/steady-state decomposition of Eq. 2.30, with beats near resonance and the resonant linear-envelope solution at ω/ωₙ=1.
Free vibration vs steady state • Beats • Resonance growth • Rd and 0°/180° phase jump
Transient/steady-state/total decomposition with viscous damping, plus Rd and phase-angle families of curves across ζ.
Frequency response • Resonance • Dynamic amplification • Phase relationships
Visualize the classical response of an SDOF system to a suddenly applied constant force, with overshoot, envelope, and damping-ratio comparisons.
Step force • Overshoot ratio • Decay envelope • Underdamped/critical/overdamped comparison
Coming Soon: Multi-degree-of-freedom and nonlinear structural dynamics demonstrations, later this semester.
Natural modes • Modal superposition • Eigenvalue analysis • Hysteresis models