Structural Engineering & Statics
where the load goes
Concept

Locked in stress — where it appears

Stress carried by a section from a stage of loading that reached it before the section had its final shape or properties. It adds to later stresses and cannot be recovered by dividing the total load by the final section modulus, so a propped and an unpropped member differ although nothing about the finished drawing does.

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

292 MPaunpropped49.3 mm at midspansteel alonecomposite186 MPapropped28.6 mm at midspancomposite

The structure that was never complete

Every analysis in this collection is of a finished structure loaded once. Real ones are built in pieces, and each piece carries whatever was present at the moment it became structural — so the stress in a member depends on when it arrived, which appears nowhere on any drawing.

structures · construction sequence 146 MPaunpropped24.6 mm at midspansteel alonecomposite93 MPapropped14.3 mm at midspancomposite

The section that changed while it was being loaded

A stress is computed from a moment and a section modulus. When part of the moment arrived while the section was a different shape, there is no single section modulus to divide by — the stresses add and the properties do not, and two identical finished beams can differ by half again in stress with nothing on the drawing to say which is which.

sections · staged section

Named alongside it

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

Composite actionConstruction sequenceCreepSuperpositionCamberContinuityDifferential shorteningIndeterminacyModular ratioPartial interactionPlane sectionsPrestress

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