The Chartership Forum

Structural Steel Design / module 19

A complete steel building

No new theory. One structure carried from brief to erection, and the thing eighteen separate modules could not show: how the decisions interact.

What you will understand

  • Identify the governing check for each member type, and say why they differ
  • Use the gap between the top two checks to decide what to change
  • Recognise a member that is carrying steel which is not working
  • Trace a decision forward and measure how much of the project it reaches
  • Explain why the decisions that travel furthest are taken with the least information
  • Write a design record that somebody else can actually review

Lessons

  1. What governs where

    Eighteen modules have each taught a check. This lesson puts four members side by side and asks which check actually decides each one — and the answers are all different.

  2. Decisions, reach, and the record

    Which decisions matter most, when they get taken, and how to leave behind something a reviewer can actually disagree with.

Module summary
  • One building, four members, three different limit states governing — each with a different remedy
  • The 9 m floor beam is a deflection problem at 56%, with bending well behind at 39%
  • Taking the restraint spacing to 9 m hands the governing role to LTB at 89%
  • Near 6 m the two are within a point of each other: that is a section problem, not a single-check problem
  • The brace runs at 33% — sized by slenderness and availability, not by force
  • The crane girder fails fatigue at 335% while bending sits at 54%
  • The crane decision is taken at the actions stage and reaches 100% of the remaining project
  • A design record without a reason and a reopening condition is a note, not a record
Teaching basis and review status

These are educational models and exercises. Check their assumptions before using the results. The full technical content and every diagram have not yet been independently verified.

Concrete and steel calculations retain their stated first-generation Eurocode teaching basis. Use the standards and amendments specified for your project; do not mix generations without an appropriate design basis.

Read the lesson register and outstanding review notes

Check your understanding

Practice

A member has checks at 88%, 84%, 40% and 22%. What is the gap between the governing check and the next tightest, in percentage points?

Practice

A 610×229×113 UB spans 9 m at 30 kN/m. What is the mid-span moment, in kNm?

Practice

A 9 m beam has its deflection limited to span/360. What is the limit, in mm?

Practice

Module 17 sized a crane girder at 384 kg/m for fatigue where strength alone wanted 123 kg/m. By what factor did fatigue increase the weight?

Practice

A decision is taken at the scheme stage — the third of seven — and its consequences reach the connections stage, the sixth. How many stages downstream does it reach?