Generated seismic and wind loads — SWBPIPE verification

Part VI · VerificationVI–B14

Part VI

Verification

B. Elements and loads · Generated seismic and wind loads

An insulated pipe has outside diameter 0.2 m, contains liquid and spans 3.0 m. The user enters seismic factors of 0.3 along X and −0.2 along Z. The user enters wind pressure of 480.0 Pa and shape factor 0.7 along Y on this span. What uniform loads should these inputs generate? Do generated loads reach the span ends in the same way as manually entered loads?

The user supplies every factor, including gravity. The calculation uses no defaults.

This page preserves a recorded benchmark and its expected values. The dated run below is not a new run of the current product.

This benchmark tests generation from explicit user inputs. It does not establish code coefficients, a coupled fluid state or mass selection for each load/reference state. Equivalent-static generators remain unsupported on the exact straight-pressure route.

Independent numerical comparison. The recorded test exercises a benchmark crate. It does not exercise the desktop product route.

Fig. VI–B14.—Generated seismic and wind loads

1.Inputs.

Illustrative values, taken from no standard and chosen so the arithmetic can be followed by hand. Most do not describe a real pipe; read them in any consistent set of units.

Quantity	Symbol	Value
Outside diameter	D_o	0.2 m
Nominal wall thickness	t_nom	0.01 m
Mill tolerance	m	0.00125 m
Material density	ρ_m	7850.0 kg/m³
Contents density	ρ_c	800.0 kg/m³
Insulation thickness	t_ins	0.025 m
Insulation density	ρ_i	120.0 kg/m³
Gravitational acceleration (user entry)	g	9.80665 m/s²
Seismic factor, global X	—	0.3
Seismic factor, global Z	—	−0.2
Wind pressure	p	480.0 Pa
Wind shape factor	C	0.7
Wind direction	—	Global Y
Span length	L	3.0 m

2.Method.

Mass per meter comes from pipe geometry. The calculation reduces wall thickness by the mill tolerance. It multiplies metal, contents and insulation areas by their respective densities, then adds the masses.

Each seismic load equals mass per meter times the user factor times entered gravity. Wind load equals pressure times shape factor times exposed diameter, including insulation. Wind acts only on the marked span. Each uniform load is divided equally between span ends.

t_eff = t_nom − m = 0.00875 m, D_i = D_o − 2t_eff = 0.1825 m, D_ins = D_o + 2t_ins = 0.25 m(1)

m′ = A_metalρ_m + A_contentsρ_c + A_insρ_i = 41.26948280649718 + 20.926934063725005 + 2.1205750411731096 = 64.31699191139529 kg/m(2)

w_seismic,X = m′ × 0.3 × 9.80665 = 189.22026861836537 N/m(3)

w_wind,Y = pCD_ins = 480.0 × 0.7 × 0.25 = 84.0 N/m(4)

F_end = wL / 2(5)

3.Results.

Mass, generated intensities and lumped end forces
Quantity	Expected
Metal area	5.257259 × 10⁻³ m²
Contents area	2.615867 × 10⁻² m²
Insulation area	1.767146 × 10⁻² m²
Mass per length	64.31699 kg/m
Seismic intensity, global X	189.2203 N/m
Seismic intensity, global Z	−126.1468 N/m
Wind intensity, global Y	84.0 N/m
Seismic end force, global X, each end	283.8304 N
Wind end force, global Y, each end	126.0 N

The case record describes these checks:

Seismic generation gives two loads, along X and Z, with the expected intensities and no findings.
Wind generation gives one load along Y with the expected intensity and no findings.
The generated loads pass the solver’s equivalent-static check as three uniform element loads.
Lumped to the span ends, the seismic X and wind Y forces at both nodes match the hand values.
With no mass input, or no marked span, generation produces no loads and reports a finding instead.

What it shows. Checks the loads or boundary conditions prepared for the solver against a hand calculation. No system is solved.

Path exercised. The benchmark calls the solver’s components directly: elements, loads, frame solver and stress recovery. It does not go through the program’s own model-to-solve path.

Agreement. Each computed value must match the reference within an absolute difference of 1.0 × 10⁻⁹ in the case’s own units. Counts and structural outcomes must match exactly. Long values are shown here to seven significant figures; the tests compare the full values in the record.

For the student

The calculation uses two different diameters. Seismic mass uses the wall reduced by mill tolerance. Wind uses the insulated outside diameter, 0.25 m instead of 0.2 m.

4.Recorded command.

This command belongs to the archived source at 462f66975d36cd10d5b8455193ada9517d28d353. Use a checkout of that exact revision. This edition did not run the command. The recorded result does not establish current product support.

git checkout --detach 462f66975d36cd10d5b8455193ada9517d28d353
cd projects/chirality-piping
cargo test --manifest-path validation/benchmarks/mechanics/Cargo.toml occloadgen_generation_matches_witness_intensities
cargo test --manifest-path validation/benchmarks/mechanics/Cargo.toml occloadgen_generated_loads_pass_boundary_and_lump_to_end_nodes
cargo test --manifest-path validation/benchmarks/mechanics/Cargo.toml occloadgen_generation_blocks_without_user_inputs_or_marked_spans

Hand calculation: validation/hand_calcs/mechanics/tp_pmm_p3_occloadgen_equivalent_static.md. Test record, with the recorded run of 2026-07-10: mech-tp-pmm-p3-occloadgen-equivalent-static.md.