Structural Engineering & Statics
where the load goes
Concept

Component method — where it appears

The procedure that treats a joint as an assembly of springs — column web in shear, flange in bending, bolts in tension — each with its own stiffness and strength. The joint's rotational stiffness is their series combination, so the softest component decides it and the strongest contributes almost nothing.

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

A joint is springs in series. The five components of an end-plate joint, with each bar the flexibility it contributes. The column flange in bending is 39.62% of the total on its own, and doubling its stiffness raises the joint's by a factor of 1.25 — while doubling the stiffest component buys 1.05. The joint's rotational stiffness is 25227.71 kN·m per radian.

A joint made of springs in series

A connection's stiffness is not a property of the connection. It is the series combination of the flexibilities of everything the force passes through — so the softest component decides, and stiffening any of the others changes almost nothing.

connections · Component method Prying against flange thickness. The ratio of bolt force to applied force, for a tee stub carrying 140 kN per bolt, as the flange thickness varies. Prying disappears above 31.91 mm and the flange has become a mechanism below 22.75 mm, where the shaded region begins and the bolt has stopped being the thing that decides.

The thickness that decides who fails

A bolt in a tee stub carries more than the load applied to it, because the flange bends and levers against its own edge. How much more, and whether the bolt or the flange is the thing that gives way, are both decided by one dimension — and the two regimes it separates fail in completely different ways.

connections · Prying

Named alongside it

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

Joint stiffnessLever armPryingBolt tensionColumn webConnectionDuctilityEnd plateFree bodyMoment connectionPlastic mechanismRotational spring

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