Structural Engineering & Statics
where the load goes
Concept

Punching shear — where it appears

The failure in which a column pushes a plug of slab through it, checked on a perimeter rather than on a section and governed by geometry rather than by strength. Its resistance goes as roughly the three-halves power of the effective depth, so depth is the effective variable and the column size very much less so.

Named by 4 essays across 3 fields — each of them below, with the objects they name alongside it.

2d = 450column7.2 m bayperimeter u₁ = 4427 mmshear to carry V = 604 kNv = 0.606 against 0.658 N/mm²92% of the resistance used

A check made on a perimeter, not on a section

Every shear check in this collection is made on a plane cut through a member. A slab sitting on a column has no such plane, because the shear leaves in every direction at once — so the check is made on a closed line, and a line grows with the column while the load grows with the square of the bay.

internal-forces · punching shear water table39.2 kN/m² upward, everywhereweight 18.7 MN6 muplift 23.54 MN · weight 18.72 MNfactor against flotation 0.80no strength appears anywhere in that ratio

A basement is a boat

Every load in this collection presses down and is resisted by strength. Hydrostatic uplift presses up, is resisted by weight, and does not care what is built on it — so the check contains no material property at all. It is a ratio of two weights, and one of them is water.

equilibrium · uplift 4 per unit lengthshear20.4moment51.8 at x = 5.10the moment peaks exactly where the shear passes through zero

The support that is not a point

A reaction is drawn as a single arrow because the equilibrium equations only need its total. Underneath the arrow is a bearing of some width, delivering a pressure over that width, and almost everything a designer would like to know about the region near a support is a consequence of the width the arrow does not have.

internal-forces · support width 600 kN180 kN·mresultant at e = 300, outside the platemiddle third154.42 kNBolts engagedbearing over 150.88 mm at 20 N/mm² · 100% of 20

The failure that is in the concrete

An anchor bolt is a steel component and its capacity is usually decided by something else entirely — a cone of concrete pulled out around it, failing in tension, in a material every other calculation on the project has assumed cannot take tension at all. The exponent in the capacity says so: it is not the square the geometry implies.

connections · anchor breakout

Named alongside it

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

Control perimeterEffective depthFree bodyLoad pathShear frictionSize effectStrut and tieAggregate interlockAnchorageBallastBase plateBearing

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