Prismatic Strut - Concrete Column Query 2

[MattyG123]

Hi All,

I'm still learning about strut and tie and had a query when it comes to prismatic struts.

In Warner's book it states: "Only in cases where the stress field cannot diverge can a prismatic strut be used, for example where a compression member is uniformly loaded across its entire surface"

So to me this is saying, a concrete column under compression (where its entire surface area is loaded), transverse tensile stresses cannot occur (compared to a bottle shaped strut).

But in the following video (

https://www.youtube.com/shorts/ZFeLlz1dSz0)

and image below it appears the column has failed due to bursting (tensile forces have developed) causing a shear type failure. But a prismatic strut cannot diverge and therefore cannot develop tensile stresses?

Am I missing something?

Thanks Guys

 

[centondollar]

The compression strut diverging means that it is not constant in width, but rather "bottle"-shaped. To use the strut-and-tie analogy, the "non-divergent strut" means that the truss member has a constant direction and size of force, while the diverging (bottle-shaped) strut signifies non-constant size and direction of the strut force. You may google e.g., "Eurocode 2, bottle shaped truss" to find out more about this topic.

Note that even if a load is perfectly uniform, it does not distribute uniformly in the member until approximately "1*side length" or "1*diameter" of depth - this is known as Saint Venant´s principle. Therefore, you must always recognize the possibility for transverse tension forces to occur.

 

[rapt]

Mattg123,

Where does it say a prismatic strut cannot have transverse tension effects? It just says it cannot follow the prismatic strut rules.

Poisson had something to say about transverse effects for members in pure compression!