Structural Engineering & Statics
where the load goes
Concept

Decay length — where it appears

The distance over which a self-equilibrating disturbance in a member dies away, fixed by geometry rather than by material. It sets how far from a load ordinary section theory becomes reliable, and how closely diaphragms or stiffeners must be spaced before one helps the next.

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

40 N/mmas appliedbendingpure torsiondistortion=++torque 60 kNm per metre · the distortional half is 30the third and fourth cases add to the second: same torque, and one of them has none of it

The section that will not keep its shape

A box girder is closed, so torsion costs it almost nothing. What an eccentric load actually does to it is something a torsion calculation contains no term for — the rectangle becomes a parallelogram, in its own plane, along the whole length of the span.

sections · box distortion 00.511.5200.20.40.60.81distance from the loaded end (depths)self-equilibrating remainder ÷ mean stressa point loadspread over h/5split in twoone depthsame resultant, same moment · one per cent left by 1.18 depths

How far a wrong load reaches

Every figure in this collection applies a load as a point, a line or a uniform pressure, and no real load is any of those. The licence is Saint-Venant's, it is usually quoted as a principle, and it is really a statement about a wavelength.

internal-forces · saint venant

Named alongside it

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

Self equilibratingSuperpositionWarpingAiry stress functionBeam on elastic foundationBimomentBox girderCross sectionDiaphragmDistortionDisturbed regionEccentricity

All concepts