0
$\begingroup$

Quote from here:

Limit state EQU, dealing with static equilibrium, is defined as: Loss of static equilibrium of the structure... considered as a rigid body, where minor variations in the [actions or their distribution]... are significant, and the strengths of... materials ... are generally not governing.

What is meant by "strengths of materials are not generally governing"? Isn't static equilibrium very much connected to strength of materials used?

Let's say we have a simple beam system like this:

enter image description here

The force on the right is trying to de-balance the beam. Calculating the moment around the central support, this moment is counteracted by supporting force by the left support. This is an equilibrium problem. The capacity of the left support dictates whether or not the beam stays in balance. But the capacity of the left support is determined by the strength of its material.

So how do the limit states EQU and STR work here? Is EQU checked here at all, since the balance of the structure is maintained by the supporting force? Would we use EQU in the case there is no downward supporting force, and the balance would be maintained by the mass of the beam between the supports?

$\endgroup$

2 Answers 2

0
$\begingroup$

Yes. the center of gravity of all the forces combined with moments on a structure must fall within the footprint of the structure.

They have given an example in the source you referred to.

The moment caused by the wind is smaller than restoring moment caused by the moment of the weight of the structure, 1600kN about its foundation CG which is 1.25m.

$\endgroup$
0
$\begingroup$

The language from your reference is a little difficult to grab, but it simply states the basics of rigid body mechanics - For any structural system, the static equilibrium is reached when the restoration (stabilizing) forces are greater than or equal to the applied (destabilizing) forces. This condition is independent of material properties.

enter image description here

Also, the "loss of equilibrium" will occur if there is no connector at support "a" (since $\sum M_{applied} < \sum M_{resist/restore}$), regardless of the properties of the beam ($A, I, E$).

enter image description here

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.