Structural Engineering & Statics
where the load goes
Concept

Reinforcement — where it appears

Material added to carry the tension a section's own material cannot, placed where the analysis says the tension is. Its position is a lever arm, so cover and bar arrangement change the capacity as directly as the area does.

Named by 3 essays across 2 fields — each of them below, with the objects they name alongside it.

the cutcompression chordtension chordstirrups in blue, struts dashedz = 495cot θ = 2.5 · 8.3 stirrups crossed · V = 563 kN from 1047 mm²/mstrut stress 8.79 N/mm² against 10.56 available

The beam that becomes a truss

Once a web has cracked in shear there is no shear stress field in it any more. There are concrete struts, two chords and whatever crosses the cracks, and the angle of those cracks is not a property of the material — it is something the designer chooses, and every quantity in the beam moves when it changes.

internal-forces · shear truss analogy 1200 kN214 kN of tiestruts at 20°0.5 huniform from here onGuyon: 0.25 P (1 − a/h) = 214 kN — the same number, from the same lever armbearing 20.0 N/mm² · once spread 5.7 N/mm²

The force that splits what it pushes on

A prestressing tendon delivers its whole force through a plate a fraction of the section deep. One depth further along the stress is uniform, and the spreading in between requires a transverse tension nobody applied — the force that splits end blocks, and the only number in the design that no equilibrium equation on the member can see.

internal-forces · anchorage zone 0.0000.0050.0100.0150.0200.0250.030010203040compressive strainstress (N/mm²)44.4 N/mm² at 0.0068unconfined: 30 at 0.002still carryingstrength × 1.48 · ultimate strain × 8.0 · toughness × 11

Squeezed sideways into a different material

Concrete in a cylinder test fails by splitting apart sideways under a load pushing it down. Put a hoop round it and the splitting has to stretch steel — and a lateral pressure of a twelfth of the strength raises the strength by half and the ultimate strain by eight.

materials · confinement

Named alongside it

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

EquilibriumFree bodyStrut and tieAnchorage zoneArchingBearing stressBurstingConcrete strengthConcrete strutConfinementCracked sectionD region

All concepts