Structural Engineering & Statics
where the load goes
Generator

The shear-truss generator

Rendered here at the parameters it defaults to, with every essay that calls it — which is the same list as the blast radius of changing it.
Flattening the truss saves stirrups and crushes the webTwo capacities against the angle of the cracks, for a web 300 mm wide with a lever arm of 495 mm. The rising line is the stirrups: a cut along the crack severs z·cot θ/s of them, so flattening the crack from 45° to cot θ = 2.5 takes the 225 kN they carry to 563 — 2.5 times as much from the same steel. The falling line is the concrete strut, whose stress is V(cot θ + tan θ)/b_w z and therefore least at 45°. They cross at cot θ = 2.44, and 550 kN is the most this section will carry however it is reinforced.1.01.21.41.61.82.02.22.40200400600800cot θ · a flatter crack to the rightshear capacity (kN)stirrupsthe strutthe lower of the two550 kN at cot 2.44at 450 kN: stirrups 2091 → 836 mm²/m, strut stress +45%

Flattening the truss saves stirrups and crushes the web. Two capacities against the angle of the cracks, for a web 300 mm wide with a lever arm of 495 mm. The rising line is the stirrups: a cut along the crack severs z·cot θ/s of them, so flattening the crack from 45° to cot θ = 2.5 takes the 225 kN they carry to 563 — 2.5 times as much from the same steel. The falling line is the concrete strut, whose stress is V(cot θ + tan θ)/b_w z and therefore least at 45°. They cross at cot θ = 2.44, and 550 kN is the most this section will carry however it is reinforced.

1 essay calls shear-truss. The drawing above is what it returns with no arguments at all; every call below passes it something, because a placement that passes nothing draws whichever member of the family the generator happens to default to rather than the one its essay argues about.

Where it is called

Changing this generator changes every one of these figures.

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 Internal forces

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.

The library, page 4 of 6 — where shear-truss sits