SWBPIPE · The open manual
Part VI · VerificationVI–C12

Part VI

Verification

C. Stress recovery  ·  Combined axial and bending stress

A straight pipe 4.0 m long carries an axial effect of 120.0 N. Known I-end shear is 4.0 N, and I-end bending moment is 8.0 N·m. A uniform load of −2.0 N/m acts along the full length. What axial force and bending moment occur at midspan? What axial and bending stresses follow? No pressure is supplied.

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

These calculations recover separate mechanics stress components. Component recovery does not establish a combined stress maximum or code stress.

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

An axial effect acts with end bending and a line load. The case tests midspan axial force, moment and separate stress components. w N 0.5L L
Fig. VI–C12.—Combined axial and bending stress

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.

QuantitySymbolValue
LengthL4.0 m
Pipe areaA6.0 m2
Axial-effect forceFa120.0 N
Displacements for the axial effect—all zero
I-end shearVy,i4.0 N
I-end bending momentMz,i8.0 N·m
Uniform local y loadq−2.0 N/m
Stationx/L0.5
Stress areaA6.0 m2
Section modulus about yZy3.0 m3
Section modulus about zZz2.0 m3

2.Method.

The axial effect is recovered as in the thermal axial case: with no displacement, the I-end axial force is Ni = 120.0. That force is combined with the given I-end shear and moment.

At midspan, x = 2.0 m, the load acting on the I-side free body runs from 0.0 m to 2.0 m. The axial force is unchanged along the pipe. The two stresses follow from force over area and moment over section modulus.

lever = x · (active length) − (active end)2 / 2 = 2.0 × 2.0 − 2.02 / 2 = 2.0(1)
Mz(x) = Mz,i − Vy,i x − q · lever = 8.0 − 4.0 × 2.0 − (−2.0 × 2.0) = 4.0 N·m(2)
σaxial = Nstation / A = 120.0 / 6.0 = 20.0 Pa(3)
σb,z = Mz / Zz = 4.0 / 2.0 = 2.0 Pa(4)

3.Results.

Expected midspan values
QuantityExpected
Midspan axial force, N120.0 N
Midspan bending moment, Mz4.0 N·m
Axial normal stress20.0 Pa
Bending stress about z2.0 Pa

The case record describes these checks:

  • The midspan stress recovery completes without being blocked and is labeled as this case’s midspan station.
  • The midspan axial force matches 120.0 N and the bending moment matches 4.0 N·m.
  • The axial stress matches 20.0 Pa and the bending stress about z matches 2.0 Pa.
  • No hoop or longitudinal pressure stress is reported.
  • The result carries the review flags the program attaches to every result.

What it shows. Compared with an independent hand calculation.

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 force, moment and stress must match the hand calculation to within an absolute difference of 1.0 × 10−9 in its own units. Labels, flags and the absence of pressure stresses are checked exactly. Long values are shown here to seven significant figures; the tests compare the full values in the record.

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/stress/Cargo.toml combined_axial_effect_and_bending_resultants_feed_station_stress_recovery

Hand calculation: validation/hand_calcs/stress/tp_phys_009_combined_axial_bending_to_stress.md. Test record, with the recorded run of 2026-07-10: stress-tp-phys-009-combined-axial-bending-to-stress.md.

Contents · Part VI · The program: swbpipe.com · MIT licence