During nonlinear seismic drift analyses, why do second‑order equilibrium effects diverge between a centroidal model versus one that honors real storey displacements?

Choices

• (A) Drift lengthens gravitational lever arms changing residual overturning amplification
• (B) Gravity overturning terminates once material nonlinearity begins
• (C) Seismic drift always erases geometric stiffness coupling
• (D) Service displacement fields never couple into collapse mechanisms