Structural Engineering & Statics
where the load goes
Concept

Free body — where it appears

A piece of a structure drawn on its own with every force the rest of the world applies to it, which is where every result here comes from.

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

00.20.40.60.8100.20.40.60.81moment ÷ plastic momentaxial force ÷ squash loadrectangle: 25.0% of Mp outside the lineI-section: 6.0% of Mp outside the linethe straight-line rule

Two ways to fail, and the curve between them

A column carrying both compression and bending has two capacities and a rule for sharing them out. The rule is a straight line, the truth is a curve, and for a rectangle the straight line gives away a quarter of the plastic moment at half the squash load.

materials · interaction 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

Named alongside it

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

Conservation of energyDynamic amplificationEccentricityEqual area axisImpact factorImpulseInteractionNatural periodNeutral axisPlastic momentPlastic neutral axisSection shape

All concepts