Area & Point Loads
How area loads (psf) and point loads compose into the line and point loads a calc uses.
Loads in Load Criteria are stored as area loads in psf. A beam or post, though, needs a line load (kip/ft) or a point load (kips). ClearSpan does that conversion for you — the math lives in one place so neither you nor the AI assistant multiplies by hand.
Area load → line load#
An area load (psf) applied over a tributary width (ft) becomes a uniform line load:
line load (plf) = area load (psf) × tributary width (ft)
line load (klf) = plf ÷ 1000
The result is a uniform load on the member, expressed in kips per foot (w) — the unit the solver works in.
Worked example#
A floor dead load of 12 psf carried over a 10 ft tributary width:
12 psf × 10 ft = 120 plf = 0.120 kip/ft
That 0.120 kip/ft uniform load is what the beam sees.
Area load → point load#
A point load is the same psf applied over a tributary area (ft²) rather than a width, landing at a position x along the member:
P (kips) = load (psf) × tributary area (ft²) ÷ 1000
The position x is geometry and never enters the magnitude — it only places the load.
Worked example#
A 40 psf load over a 120 ft² tributary area:
40 psf × 120 ft² ÷ 1000 = 4.8 kips
Building up a tributary area#
You don't have to pre-compute the area. You can describe it as a sum of products of named dimensions read off a drawing, and ClearSpan resolves the arithmetic. For example, dimensions a = 10, b = 12, c = 8, d = 5 with terms a·b + c·d + a·c:
(10 × 12) + (8 × 5) + (10 × 8) = 120 + 40 + 80 = 240 ft²
When a build-up is provided it is authoritative; a single area_sqft number is used otherwise.
Recording the dimension build-up preserves how the area was derived, so the provenance shows in the report instead of just a bare number.
Where the load goes#
Each derived load comes back as a ready-to-use load object — a uniform load (type: uniform, with w) or a point load (type: point, with P and x) — tagged with its category. On save, the magnitude is recomputed authoritatively from the derivation, and the derivation block is persisted so the calc and report can show where the number came from.
To pull these values from your project's Load Criteria rather than transcribing them, see Link Loads into a Calc.