Structural Engineering & Statics
where the load goes
Concept

Asymmetric section — where it appears

A section whose centroid is not midway between its extreme fibres, so it has two elastic section moduli and its strength depends on the sign of the moment.

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

the same, laid flatZ top 7.5 × 10³Z bottom 7.5 × 10³the same both wayssquareZ top 27.4 × 10³Z bottom 27.4 × 10³the same both waystall rectangleZ top 100.0 × 10³Z bottom 100.0 × 10³the same both waysI-sectionZ top 242.9 × 10³Z bottom 242.9 × 10³the same both waysthe two solid lines are the extreme fibresthe bar is the smaller section modulus, to scale

Two strengths, depending which way up

A symmetric section has one section modulus. A tee has two, differing by a factor of three, so the same member has two bending strengths and which applies is decided by the sign of the moment. Turn it over and it is a different beam.

sections · asymmetric section the same, laid flatr = 4.3 mmλ = 9247 kNsquarer = 15.8 mmλ = 25397 kNtall rectangler = 57.7 mmλ = 691295 kNI-sectionr = 90.0 mmλ = 443146 kNthe dashed pair is ±r about the centroidthe bar is the Euler load at 4 m, to scale

The one length a section takes into a column

A section has an area, a second moment, two section moduli, a shear centre and a torsion constant. A column has heard of exactly one of them, and it is none of those — it is the length √(I/A), which is where the whole area would have to sit to give the section the stiffness it has.

sections · radius of gyration

Named alongside it

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

Second moment of areaBucklingBuilt up columnBuilt up sectionCentroidEffective lengthElastic section modulusEqual area axisEuler loadExtreme fibreMinor axisNeutral axis

All concepts