Module 18
AI and machine learning for structural engineers
What a trained model is, what it cannot know, and where it belongs beside a deterministic method rather than instead of one.
What this module covers
- Say what machine learning is doing, in terms an engineer can check
- Distinguish supervised, unsupervised and reinforcement learning by what each needs
- Explain overfitting through the training and test error curves
- Show that class imbalance destroys recall while accuracy stays respectable
- Explain why a model gives no signal that it is extrapolating
- State where AI belongs in structural work, and where it does not
- Apply the rule that a deterministic check, where one exists, must have been run
Lessons
Fitting a function to samples — and what that implies about every claim made for it.
Start lesson →Why training error falls forever, why test error turns round, and why the gap is invisible from the training data alone.
Start lesson →Class imbalance, distribution shift, and the two numbers that behave completely differently.
Start lesson →A fast approximation to a slow analysis — what it buys, what it costs off the edge of its data, and the rule that governs its use.
Start lesson →
Module checkpoint
Check what you have taken in
5 questions
Question 1
A model is proposed to predict bending moments in continuous beams, trained on 50 000 analysis results. What is the strongest objection?
Question 2
A balanced classifier achieves 95.0 % recall on a class. After the training set for that class is cut from 80 examples to 3, its recall falls to 26.7 %. By how many percentage points has it fallen?
Question 3
A study of 200 combinations at 20 minutes each is replaced by 40 training runs, surrogate evaluation, and 10 confirming runs. What percentage of the original analysis time does that use?
Question 4
A classifier is tested on 800 models, of which 40 have a defect. It flags 30 correctly and misses 10. What is its accuracy if it raises no false alarms at all?
Question 5
Which single figure should be asked for first when a machine-learning tool is offered for structural work?