Structural Engineering & Statics
where the load goes
Concept

Moment rotation — where it appears

The relation between the moment a connection transfers and the angle it turns through, which classifies it as pinned, rigid or semi-rigid. The boundaries are multiples of the beam's own stiffness, so the same detail is rigid in a short stiff member and semi-rigid in a long slender one.

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

00.0050.010.0150.020.0250.030.0350.040.0450.05050100150200rotation, radiansmoment, kN·mrigid abovepinned belowweb cleats — pinnedflush end plate — semi-rigidextended end plate — semi-rigid

Neither pinned nor rigid, which is every real connection

Frame analysis offers two options for a joint and reality supplies a continuum between them. Worse, the boundaries are not properties of the connection at all — the same end plate is rigid on a short stiff beam and semi-rigid on a long slender one.

connections · joint stiffness 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.

ConnectionJoint stiffnessBolt groupClassificationContinuityContraflexureDuctilityFlexural rigidityLoad pathLoad sharingMoment redistributionNet section

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