Module 16
Multi-storey steel buildings
Everything repeats. A decision about a floor zone is made once and paid for on every storey, which is why the most consequential choices in a multi-storey building are made before any member is sized.
What this module covers
- Compare floor systems on floor ZONE rather than structural depth
- Say why services through the structure change the arithmetic entirely
- Quantify what a floor-zone saving is worth once multiplied by the storeys
- Apply the imposed-load reduction and say what it acknowledges
- Compare the lateral stability systems on the terms that decide between them
- Say why a braced bay is nearly always the engineering answer and often not the chosen one
Lessons
The decision that matters is the floor zone, not the beam depth — and whatever you decide, you will pay for it once per storey.
Start lesson →A braced bay is 17 times more efficient than a moment frame and is regularly rejected. Understanding why is most of what a multi-storey stability decision involves.
Start lesson →
Module checkpoint
Check what you have taken in
8 questions
Question 1
A downstand beam is 450 mm deep with 350 mm of services below and 250 mm of finishes. What is the floor zone, in mm?
Question 2
A 200 mm saving per floor on a 15-storey building with a 160 m perimeter saves how much façade, in m²?
Question 3
A column carries 6 storeys. With αn = (2 + (n − 2) × 0.7)/n, what is αn?
Question 4
A column carries 400 kN permanent and 300 kN imposed unreduced. With αn = 0.80, what is its design load, in kN?
Question 5
A storey has αcr = 15. Its bracing is replaced by a system one third as stiff. What is αcr now?
Question 6
System A has relative stiffness 2.5 at cost 0.6; system B has 0.6 at cost 1.4. What is A's stiffness per unit cost, relative to B's?
Question 7
Why should a floor system be compared on floor ZONE rather than structural depth?
Question 8
In what order should the major decisions on a multi-storey steel building be made?