Structural Engineering & Statics
where the load goes
Concept

Shear friction — where it appears

Shear carried across a crack by the roughness of its faces, clamped together by reinforcement that is stretched by the crack opening as it slides. The capacity is the clamping force times a friction coefficient that stands for roughness, so the reinforcement crossing the crack works in tension and the concrete works in compression against it.

Named by 3 essays across 2 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 36shearthe bars clamp, and do not carryasperity slope 54° · tan = 1.40clamping stress 2.50 N/mm² · resistance 3.50 N/mm²sliding without separating is not available to a rough crack

Shear across a crack that is already there

Every shear calculation in this collection starts from an uncracked solid — a principal stress, a shear flow, a diagonal tension. This one starts after the crack, on a plane with no tensile strength at all, and the coefficient it uses is not a coefficient of friction. It is the slope of the roughness.

internal-forces · shear friction 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.

Aggregate interlockAnchorageClamping forceFailure surfacePunching shearSize effectStrut and tieBase plateBreakoutBrittlenessCapacity designColumn head

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