How to find the first area moment of inertia (Q) for an I-beam with flanges

Click For Summary
SUMMARY

The discussion focuses on calculating the first area moment of inertia (Q) for an I-beam with flanges. Two methods are presented: the first method requires using twice the thickness of the web (10 mm), while the second method utilizes the web thickness (5 mm). For accurately determining Q at point 'a', the second method is confirmed as the correct approach. This distinction is crucial for engineers and designers working with structural analysis.

PREREQUISITES
  • Understanding of I-beam structural properties
  • Knowledge of shear stress calculations
  • Familiarity with area moment of inertia concepts
  • Basic principles of mechanics of materials
NEXT STEPS
  • Research the calculation of shear stress in beams
  • Study the properties of I-beams and their applications
  • Learn about the significance of the area moment of inertia in structural engineering
  • Explore advanced methods for analyzing shear forces in structural components
USEFUL FOR

Structural engineers, civil engineering students, and professionals involved in the design and analysis of beam structures will benefit from this discussion.

hannahNeum
Messages
1
Reaction score
0
Homework Statement
To find Q at point a, should the total area above a be used as the area, of just the area above a on the right flange?
Relevant Equations
First area moment of inertia:
Q=∑ȳA

Should I use:
Q=(31.25mm)*(12.5mm*5mm*2)

or

Q=(31.25mm)*(12.5mm*5mm)
I beam.png
 
Physics news on Phys.org
You can do it either way if you are looking for the shear stress at ‘a’, but use twice the thickness of the web (10 mm) using the first way and use just the web thickness (5 mm) when using the second way. If it is just Q you are looking for at ‘a’, then the 2nd way is correct.
 

Similar threads

  • · Replies 5 ·
Replies
5
Views
4K
  • · Replies 8 ·
Replies
8
Views
2K
  • · Replies 12 ·
Replies
12
Views
2K
Replies
3
Views
2K
  • · Replies 4 ·
Replies
4
Views
3K
  • · Replies 5 ·
Replies
5
Views
1K
Replies
5
Views
4K
  • · Replies 7 ·
Replies
7
Views
11K
  • · Replies 10 ·
Replies
10
Views
3K
  • · Replies 2 ·
Replies
2
Views
2K