Midas FEA linear dynamics and buckling analyses are the manual's linear static, modal, time history, response spectrum, and eigenvalue buckling procedure family.
How It Works
Linear static analysis solves the assembled stiffness equation with loads, boundary conditions, coordinate transformations, and singularity checks. The manual also warns that nonlinear member cases such as tension-only or compression-only links use internal iteration, so their results should not be combined as if they were purely linear load cases.
Modal analysis solves K phi = lambda M phi and reports mode shapes, participation factors, effective modal mass, and modal direction factors. Lanczos and subspace methods are described, including shift-invert ideas, rigid-mode handling, and Sturm sequence checks for missed eigenvalues.
Time history analysis is organized through mode superposition and direct integration, with damping models such as Rayleigh damping and modal damping. The manual gives a practical time-step accuracy rule: choose a step small enough relative to the highest mode of interest and the load time interval.
Response spectrum analysis approximates a multi-degree-of-freedom response through modal single-degree-of-freedom spectra and modal combination rules such as ABS, SRSS, and CQC. Linear buckling analysis forms a geometric stiffness contribution from a pre-buckling stress or internal force state and solves an eigenvalue problem for critical load factors and modes.
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