load distribution angle - concrete

[BauTomTom]

Hallo

I would like to ask if somebody knows how to determinate the load distribution angle by concret. See attached graphic there I drawed four different cases. I know from the university it was something like 60 degree but does it applie everywhere?

How does the concrete strenght influes it?

How does the reinforcement influence it?

Regards

BauTomTom

 

[csd72]

A- depends on code
B - irrelevant, corbel needs to be designed properly as a strut and tie structure.
C - 30 degrees usually for masonry
D - 45 degrees is accepted practice in most countries and has been enshrined in british code for the last couple of decades. Works well when you have low stress though I would be cautious to use these when you have very high bearing pressure (e.g. rock) or are designing a pile cap.

 

[BauTomTom]

TO CSD72:

so it is actually not so easy to say it.
in CASE A: it actually shouldn't depend on the code this shoulb be just the concrete properies. If you woudl know the angle here then you coudl actually cut this "dead concrete" away

in CASE B: why I ask is, so that you could optimize the bottom of the corbel as well the angle

TomTom

 

[MiketheEngineer]

Ditto

 

[a2mfk]

Basically agree with CSD.

This is a revolving door question on this forum, with the most common answers usually being 30-45 degrees to each side of a point load for distribution into a CMU, brick or concrete wall. You will see different things in different textbooks, I don't know if I have ever seen this addressed in a US code. You have to assess each situation, and I would tend to be more liberal with a CIP concrete wall then CMU. Then depends on the age, condition, are there cracks, how big is the load, etc. (good ole engineering judgment)...

 

[YimYames]

I think it is important to assess the concrete's deformation abilities in each case. As an example, a concrete footing on rock will not be able to distribute the load at 45 degrees.

 

[BauTomTom]

and what if we check it in FE? will a FE program not show then the unstressed element? then we would see the angle.
Unfortunately I don't have such an program and also not the knowledge how to deal with it

TomTom

 

[rscassar]

The strut-tie provisions in AS3600-2009 allows up to 60 degrees for ordinary reinforced concrete (that is 2H:1V for vertically applied loads) and 70 degrees for prestressed concrete (almost 3H:1V for vertically applied loads)

 

[BauTomTom]

60 or even 70 degree? this is a lot.
so why do they teach us in the university 45 degree?

would a FE programm show it correctly?

TomTom