Skip to content
Queensferry

Module 01

Structural steel as a material

What steel actually does when you load it, and why almost every surprising rule in steel design traces back to one fact: the grade changes the strength and leaves the stiffness alone.

What this module covers

  • Explain why steel is used structurally, and what it is bad at
  • Read a stress–strain curve and say what each region allows a designer to do
  • Explain why a higher grade helps some members and almost none of the others
  • Describe residual stresses and say where they come from
  • Explain why thicker product is weaker
  • Recognise toughness, brittle fracture and lamellar tearing as separate problems

Lessons

  1. 1.1

    What steel does when you load it

    The stress–strain curve, region by region, and what each one lets a designer get away with.

    Start lesson →
  2. 1.2

    Residual stress, thickness and toughness

    Three properties that are invisible in a tensile test, absent from most calculations, and responsible for a surprising share of what goes wrong.

    Start lesson →

Module checkpoint

Check what you have taken in

6 questions

  1. Question 1

    What is the strain at first yield for S275 steel, as a percentage? Take E = 210 000 N/mm².

  2. Question 2

    A beam in S275 fails its deflection check by 20%. It is changed to S460. By what percentage does the deflection improve?

  3. Question 3

    What is ε for S355 steel at a thickness of 20 mm?

  4. Question 4

    A section has residual compression at the flange tips of 0.3 fy. Expressed as a fraction of the squash load, at what load does the section begin to lose stiffness?

  5. Question 5

    S460 steel fails at about 15% strain. By what factor does it stretch past its elastic limit? Take E = 210 000 N/mm².

  6. Question 6

    In pure shear, at what fraction of fy does steel yield on the von Mises criterion? Give the fraction.