Module 12
Bolts, pins and welds
A fastener does not have a resistance. It has several, belonging to different failure modes in different materials — and which one governs decides what would actually help.
What this module covers
- Say what happens at a bolt in shear, and why bearing is a separate check
- Explain why a higher bolt grade often buys almost nothing
- Recognise punching shear and prying, the two modes people forget
- Explain what a preloaded bolt does differently, and why it is not chosen for strength
- Size a fillet weld on its throat, and say what the directional method adds
- Say what each detailing rule protects, rather than memorising the number
Lessons
The bolt can shear, the plate can tear, the head can punch through, and a flexible plate can pry. Each is a different calculation with a different remedy.
Start lesson →A preloaded bolt does not carry shear at all. A fillet weld is smaller than it looks. And every spacing rule is protecting a number in a calculation you have already done.
Start lesson →
Module checkpoint
Check what you have taken in
8 questions
Question 1
An M24 grade 8.8 bolt has As = 353 mm², threads in the shear plane. What is Fv,Rd in kN? Take αv = 0.6, γM2 = 1.25.
Question 2
A bolt group has bolt shear 94 kN and ply bearing 60 kN per bolt. Six bolts carry the load. What is the group's resistance, in kN?
Question 3
What is the throat of a 10 mm equal-leg fillet weld, in mm?
Question 4
A 6 mm fillet gives 1067 N/mm longitudinally. What does a 200 mm run on each side of a plate give in total, in kN?
Question 5
A weld leg is doubled from 6 mm to 12 mm. By what factor does the deposited weld metal increase?
Question 6
An M20 bolt takes a 22 mm hole. What is the minimum end distance at 1.2 d₀, in mm?
Question 7
A bolted connection is governed by ply bearing. Which change would help most?
Question 8
Why is a fillet weld's strength taken on its throat rather than its leg?