Masonry Arching Action
Masonry Arching Action
(OP)
Has anyone seen any methods for determining thrust or how much masonry is needed on the side of an opening to consider arching action.
It was late and I doodled what I thought may be an appropriate method for determining the length of wall required each side of an opening. Only problem is that it is not much and I'm not sure I have given it enough thought so I apologize in advance if I'm way off. I should also mention I did not apply a live load, only self weight.
It was late and I doodled what I thought may be an appropriate method for determining the length of wall required each side of an opening. Only problem is that it is not much and I'm not sure I have given it enough thought so I apologize in advance if I'm way off. I should also mention I did not apply a live load, only self weight.






RE: Masonry Arching Action
The arch as usual is not of big section since efficient. Normally it is a matter of the extreme piers taking the horizontal push, see what degree of tensile action appears in the (always to be) cemented masonry. I quite likely wouldn't accept there but 0.15 MPa tensile stress in the masonry under factored loads.
RE: Masonry Arching Action
I think you could approximate the thrust as equal to the vertical load that is corbeling(sp?) over the lintel for the 45 degree you show. The flatter the slope you assume the higher the thrusts get.
RE: Masonry Arching Action
EIT
www.HowToEngineer.com
RE: Masonry Arching Action
Dik
RE: Masonry Arching Action
For simplicity let us assume 45 deg. Also for discussion purposes let us assume the opening is 8'-8" wide, lintel is 10 feet long with 8" bearing on each side. The wall height is 10 feet above the top of lintel.
For design of 8" high lintel - self weight + triangular weight of masonry(2000#). Lintel will be designed as a regular concrete flexural member with effective depth of about 6inches. Even if masonry lintel block is proposed, the design approach for the lintel would remain the same.
For thrust on the pier on either side, I agree with dcarr82775. - Total weight of masonry for arching = (10' x 10' @ 80 - 2000#) = 6000#. Thrust on each pier @ 45 deg will be about 3000#.
If hollow unreinforced masonry is used for piers, then shear will be calculated using (V.Q/In.b) and not just (V/An). We always use fully grouted reinforced piers.
Arching action also requires adequate depth of masonry above the apex of the triangle. Moreover, if floor loads are applied below the apex of the triangle, no arching is considered and the lintel is designed for load from the wall to the underside of the floor directly above and the load from the floor directly above.
RE: Masonry Arching Action
What I am trying to determine is how much wall is needed each side of the lintel so that arching may be considered. This is why I was using the face shell width only to resist shear/thrust.
What are you thoughts on this? Would you say that the pier can resist this thrust? Would you then check the pier as if it had a point load (the thrust) applied at the elevation of the lintel and in the plane of the wall (sorry kinda thinking out load here)?
EIT
www.HowToEngineer.com
RE: Masonry Arching Action
Check out BIA Technical Note 31A
I've attached it and here is the link:
Link to BIA Tech Notes
RE: Masonry Arching Action
RE: Masonry Arching Action
RE: Masonry Arching Action
@JAE Thanks I will have a look through the article.
I'm trying to finish up that partially grouted shearwall calc. It seems there are many different ways you can skin that cat.
EIT
www.HowToEngineer.com
RE: Masonry Arching Action
See attached comparison. If you have time let me know your thoughts.
Thanks again!.
EIT
www.HowToEngineer.com