Structural Engineering & Statics
where the load goes
Concept

Plastic redistribution — where it appears

The transfer of moment from a yielded region to one still elastic, which continues until enough hinges have formed to make a mechanism. It is what allows a plastic analysis to reach a collapse load above first yield, and it requires rotation capacity the section has to be detailed for.

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

A bolt group under an eccentric load. A 3 by 2 bolt group carrying 100 kN at 150 mm from its centroid, with the resultant force on each bolt drawn to scale, by the elastic vector method. The load is shared equally and the torque is not, so the worst bolt carries 50.37 kN against 16.67 kN of direct shear alone — 3.02 times as much.

The bolt that carries more than its share

Six bolts, one hundred kilonewtons, and a worst bolt carrying fifty. The load is shared equally and the torque is not, and the second one is invisible on any drawing where the connection is a point.

connections · Bolt group Throat stress round a fillet weld group. A l shape weld group carrying 150 kN at 200 mm from its centroid. The peak throat stress is 2.17 kN per mm of throat, at (139.53, 100); the worst point at maximum radius from the centroid carries 1.99. Checking by radius is wrong here by 9.17%, and points at identical radius differ by a factor of 1.

The radius rule, and where it fails

A weld group under an eccentric load is checked at the point furthest from its centroid, on the reasoning that the stress from the twist grows with the radius. That reasoning ignores the direction the two stresses point in, and for one common shape it misses the peak by nine per cent.

connections · Weld group

Named alongside it

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

Bolt groupEccentricityInstantaneous centrePolar second momentTorsionConnectionElastic methodFillet weldFree bodyMoment armThroat stressVector sum

All concepts