Concept

Amplification — where it appears

The factor by which a second-order analysis multiplies a first-order deflection, equal to one over one minus the load ratio. It is more usefully read as a softening than as a magnification, because a stiffness that has fallen changes how load divides between parallel systems and a magnified deflection does not.

Named by 2 essays across one field — each of them below, with the objects they name alongside it.

The column that fails years later

A concrete column under sustained load goes on straining at constant stress, so its deflection grows — and because the second-order moment is the load times that deflection, the demand grows with it. There is a load below which the two settle and one above which they never do.

stability · creep buckling

The stiffness the load takes away

Buckling is usually taught as an event — a critical load, a bifurcation, a mode. Written as a matrix it stops being an event at all. A compressive load subtracts a stiffness from the structure, the subtraction grows with the load, and the critical load is simply where what is left reaches zero.

stability · geometric stiffness

Named alongside it

The objects these essays reach for when they reach for this one.

Buckling Second order Compatibility Creep Creep buckling Critical load Degrees of freedom Divergence Duration of load Eccentricity Effective length Effective modulus

All concepts