Structural Engineering & Statics
where the load goes
Concept

Bond — where it appears

The shear stress between a reinforcing bar and the concrete around it, which is what transfers force between them. It is carried by the ribs bearing on the concrete rather than by adhesion, so its limit is usually a splitting of the cover, and it acts over a length rather than at a point.

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

01020304050050100150200250mid-span deflection (mm)moment (kNm)uncrackedthe memberfully crackedM_cr = 47 kNm34.2 mm at service, span over 234

Stiffer than its cracked section says

At a crack the concrete below the neutral axis has gone and the steel carries the tension alone. Between the cracks it has not gone — bond drags it back into tension, the steel strain drops, and the curvature averaged over a length of beam is neither section's.

deflection · tension stiffening 137 kN806 mm = 40φ00.20.40.60.8100.20.40.60.81along the embedded length÷ its own peakelastic forceuniform forceelastic bond stressuniform bond

The force that arrives along a length

A bolt takes its force at a hole and a weld along a line. A reinforcing bar has no such place — it is a smooth cylinder in a hole of its own shape, and the only thing stopping it sliding out is a stress smeared over its surface. So the force in it is not a number, it is a function of position.

internal-forces · bond 800 kN1.091.010.960.940.940.961.011.09an equal share490 mm = 24.5 dworst bolt 109 kN against a nominal 100 kN

The bolts that do not share

Every bolted connection in this collection has divided a force by a number of bolts. That is right for a short joint and wrong for a long one, and the reason has nothing to do with the bolts — it is that the plates they join are elastic, and stretch by different amounts at different points along the lap.

connections · long joint

Named alongside it

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

Decay lengthDuctilityEquilibriumFree bodyLap spliceReinforcementShear lagStiffnessAnchorageBearingBolt groupCompatibility

All concepts