Solid Mechanics as applied to B31 piping codes

A: A: Sustained load case is SL ≤ Sh. That's the check. B: Occasional loads are a separate load case, not a prerequisite. C: Sc applies to cold conditions, not operating. D: Pressure longitudinal stress is already part of SL; double‑counting it is a classic spreadsheet error.

A: A: Support stiffness directly drives load paths. Ignoring it invalidates results. B: A rigid vs constant spring flips how weight and displacement are shared, which shifts both SL and SE. C: Nozzle loads change, but the line stress state changes too. D: Springs control sustained load and displacement, not just fatigue.

A: A: Internal pressure pushes outward; it doesn't ovalise inward. B: Restraint causes axial stress, not shell collapse. C: Vacuum or low internal pressure with ambient external pressure drives buckling in thin walls. D: Fatigue leaves cracks, not global ovalisation.

A: A: SA = 1.25Sc + 0.25Sh = 1.25×138 + 0.25×120. B: That's using Sh twice. C: That's using Sc twice. D: That's treating it like a pressure allowable with safety factors stripped out.

A: A: Hoop stress doesn't open a gasket. B: Rotation unloads the gasket even when code stress looks fine. C: Material issues usually show blowout or creep, not repeatable leaks after alignment. D: A class mismatch would fail immediately, not intermittently.

A: A: Corrosion allowance is handled separately. B: Process piping runs hot and moves; the code philosophy reflects that. C: Material strength varies in both codes. D: Both address fatigue, just through different mechanisms.

A: A: Unreinforced tees carry high SIFs; missing that hides peak cyclic damage. B: The error usually goes the other way. C: Pressure checks are separate and usually conservative. D: Corrosion matters, but it doesn't explain branch cracking on its own.

A: A: Nominal only works on paper. B: That's after mill tolerance but before corrosion. C: 9.27×0.875 − 3 mm is the effective section. D: That's subtracting corrosion twice.

A: A: Vibration cracks, it doesn't accumulate plastic strain. B: Sustained load plus cyclic displacement causes incremental strain each cycle. C: Creep needs higher temperature and shows necking or rupture. D: Brittle fracture is sudden, not progressive.