Structural Engineering & Statics
where the load goes
Concept

Shock spectrum — where it appears

The peak response of a single-degree-of-freedom structure to a transient load, plotted against the ratio of the load's duration to the structure's own period. It divides the answer into an impulsive regime where only the impulse matters and a quasi-static one where the dynamic factor approaches two.

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 00.511.522.500.511.52load duration ÷ natural periodpeak ÷ static deflectiontwice the static answerthe static answera load that rises linearly, then staysa rectangular pulse, then nothing

The load that is over before it has moved

A blast delivers an enormous pressure for a few milliseconds. Everything else in this field asks what force a structure can carry; a load that has come and gone before the structure has travelled any distance is not asking that question, and the answer turns out to depend on the mass and the ductility with the strength barely in it.

dynamics · blast

Named alongside it

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

Dynamic amplificationImpulseNatural periodBlastBound theoremsConservation of energyDampingDuctility demandEnergyFree bodyHysteresisImpact factor

All concepts