Continue to Site

Eng-Tips is the largest engineering community on the Internet

Intelligent Work Forums for Engineering Professionals

  • Congratulations SDETERS on being selected by the Eng-Tips community for having the most helpful posts in the forums last week. Way to Go!

Bending Force calculation on Reinforced bar bundles

AiyushG

Student
Apr 1, 2025
4
Hi,
I need to calculate the Bending Force required to bend a reinforced bar bundle.

The bundled bar is in 12M in length with each individual bar having a diameter of 32mm having 15 Bars in the bundle which weighs approx 1136 kg. The yield strength is 650 MPa.
How to calculate the bending force when it's a bundle and not a single bar

Need some help formulating and calculating it Bar Bundle Bending.png
 
Replies continue below

Recommended for you

Could you supply a picture of the cross section and explain how they are joined together. Also a FBD would be informative.
 
They are tightly Bundled using steel straps at the manufacturing units. Making an outer circle of large diameter containing 15 smaller circles of 32 mm dia
 
What is dictating the behavior of the bundle with 15 Bars is a compound section?
If only some friction provided , assuming each bar is separate beam will be safe and reasonable approach.
 
They are bundled at multiple points about 9-10 straps. Making them to be considered as a compound section i guess. Yes, there's friction for sure as they are ribbed bars used for construction.
 
Is it a right approach to consider actual area covered by the bars i.e. N×(pi*d^2)/4 then the cumulative diameter shall be sqrt(N×d2)

Assuming them as a compound bar, calculating bending moment
M = Yst × I / c
 
Not to be that guy, but aren't student posts supposed to be limited to the student forum?
 
The required bending moment for fully plastic deformation will be somewhere between 15 times the moment of plasticity ((d^3/6)*yield_stress) of a single bar, and that of the entire cross section, which would be about 3 times bigger.

But the bundle will be permanently bent once the outer fibres yield.
 
Is it a right approach to consider actual area covered by the bars i.e. N×(pi*d^2)/4 then the cumulative diameter shall be sqrt(N×d2)
No..
It is true that the total area of the bars = N×(pi*d^2)/4
If you want to find the MOI of the assembly section, ( probably hexagonal) you must apply paralel axis theorem.
 
The minimum inertia based on the possible stack arrangement and rotation position should be used.
 

Part and Inventory Search

Sponsor