A random vibration analysis in a finite element code will happily report an RMS von Mises stress, or an RMS resultant shear force in a bolt, and the analyst will happily multiply it by three and compare it against an allowable. Both quantities are useful.… Read more
A change to a single equation in ASME B31.3 has meaningful consequences for how piping displacement stress is evaluated in high-cycle service. The change is small in appearance and large in effect, and it is worth understanding both the arithmetic and the seventy years of… Read more
Structures subjected to random vibration environments are routinely evaluated for stress using the von Mises criterion, which condenses the full multiaxial stress state into a single scalar suited for comparison against a yield or fatigue allowable. But von Mises stress is a nonlinear function of… Read more
Pointed Gothic arches framing the choir, Notre-Dame de Paris. Smooth and Pointed Arches: Loads, Stress, Fracture, and Fatigue Introduction The accompanying photograph shows the interior of Notre-Dame de Paris, where every opening is spanned by a pointed arch. Stand in a Roman basilica instead and… Read more
Introduction Uniaxial fatigue methods, whether stress-life, strain-life, or spectral, presume that a single stress or strain component tells the whole damage story. Real hardware disagrees. Shafts carry bending plus torsion, pressure vessel nozzles see biaxial membrane stress plus thermal bending, and vibrating structures respond in… Read more
A reader recently asked a sharp question in the comments on one of my posts: what’s the best analysis approach for determining thermally induced stresses and forces in reinforced concrete structures, given that standard commercial workflows using software like ETABS seem far from robust and… Read more
Union Pacific has begun spraying white paint on the sides of its rails in the hottest sections of its 32,000-mile network. The program, which entered targeted deployment in 2025, uses a hi-rail truck with a spray rig to coat both faces of the rail web… Read more
Image credit: https://www.sintechnology.com/portfolio-articoli/hole-drilling/ Drilling a hole into a structure is normally something an engineer tries to avoid — holes are stress concentrators, fatigue initiation sites, and sources of structural weakness. But in one important application, drilling a small hole is precisely how engineers measure the… Read more
One of the most counterintuitive repair techniques in structural engineering is also one of the oldest: to stop a fatigue crack from growing, you drill a hole at its tip. Adding material loss to an already cracked structure seems like exactly the wrong prescription —… Read more
By Tom Irvine While enjoying a glass of orange juice at an outdoor café in Madeira, Portugal on a sunny Independence Day morning, I noticed the reusable stainless steel straw resting across the glass — its elegant curved bend a perfect reminder that one of… Read more