Structural Engineering & Statics
where the load goes
Concept

Contraflexure — where it appears

A point along a member where the bending moment passes through zero and the curvature changes sign. Its position is a property of a load case rather than of the structure, so a splice placed there carries no moment for one arrangement of load and some for every other.

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

w = 20 kN/mcorner 65.2 kNmmidspan 94.8 kNm94.8 + 65.2 = 160.0 = wL²/8

The moment that goes round the corner

At a rigid knee the bending moment does not stop at the end of the beam. It turns and runs down the column, and in the same instant the beam's shear becomes the column's axial force — while the block of steel that has to carry the turn appears on no member diagram anywhere.

internal-forces · corner moment 800 kN1.161.050.970.920.890.890.920.971.051.16an equal share675 mm = 33.8 dworst bolt 93 kN against a nominal 80 kN

The joint that has to be as good as the member

A splice exists because members come in lengths and structures do not. It has to deliver the same force, at the same stiffness, in the same distribution across the section, through a discontinuity — and each of those three requirements is met by a different feature of the detail, with the third one usually left to look after itself.

connections · splice

Named alongside it

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

ContinuityBolt groupConnectionDuctilityFree body diagramHaunchJoint stiffnessLoad pathLoad sharingMoment connectionMoment rotationNet section

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