Structural Engineering & Statics
where the load goes
Concept

Hoop tension — where it appears

The circumferential force in a curved wall carrying internal pressure, equal to the pressure times the radius. It arrives with no lever arm, contains no wall thickness, and is settled by a free body of half a ring cut along a diameter.

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

NN2R = 0.60 m — the projected widthp = 1 MPap · 2R = 2N ⇒ N = pR = 300 kN/mno thickness in it, no second moment, no length

The force that is only a radius

Every internal force in this collection arrives with a lever arm attached. A hoop force does not. Cut a cylinder along a diameter and the free body settles it in one line — pressure times radius, with no thickness, no second moment and no length in it — which is why a tank wall is thin and why its worst hoop force is not at the bottom.

internal-forces · hoop tension 0123400.20.40.60.81liquid depth ÷ radiusfraction of the liquidwith the wallslosheslever ÷ Hthis tank: H/R = 1.33, 65% impulsive

The liquid has a period of its own

Shake a tank and its contents do not all go with it. Part of the liquid moves as though it were bolted to the wall and part sloshes at a period fixed by gravity and the radius, which the tank's stiffness has no influence over whatever. The split is decided by one proportion, and the two parts then take entirely different amounts of the earthquake.

dynamics · sloshing

Named alongside it

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

Free bodyMembrane actionBase shearBending momentBoundary layerConvective massCrack controlDomeEigenvalueEquilibriumFreeboardImpulsive mass

All concepts