Structural Engineering & Statics
where the load goes
Concept

Impulse — where it appears

The area under a force-time curve, which is what a structure responds to when the load is over before it has begun to move. For a load over before the structure has begun to move, only its area matters and its shape does not, which is why a blast is described by an impulse and a wind by a pressure.

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

012345-30-20-10102030time (s)displacement (mm)20 kN applied at once and heldthe load arrives in no time at allstatic, 12.67 mmpeak 24.56 mm at 0.250 s

Twice the deflection, for the same load

A weight placed gently on a beam deflects it by one amount. The same weight let go from rest, a millimetre above the same beam, deflects it by twice as much — and the factor of two is exact, for every structure ever built.

dynamics · dynamic amplification 05101520253035400246810drop height ÷ static deflectionpeak ÷ static deflectiontwice the static answer — a weight placed, not droppedthe static answera weight dropped from a height

The weight that was dropped

A half-tonne load lowered onto a beam produces 5 kN. The same load dropped one metre onto the same beam produces 160 kN — and onto a beam ten times softer, 54 kN. The stiff structure is the one that suffers, which is the opposite of every other rule on this site.

dynamics · impact factor

Named alongside it

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

Conservation of energyDynamic amplificationImpact factorStrain energyCrane loadingFall arrestFree bodyNatural periodShock spectrumStiffness

All concepts