Arch Action of mass concrete

[sybie99]

Hi Guys

I have a situation where mass concrete with minimal reinf must bridge a opening. In masonry where you have a door or window opening, the bricks will "arch over the opening at 45degrees and the lintel will only need to carry the triangle of masonry above it.

My question is, will mass concrete act the same? In other words will it arch over the opening at 45degrees (more or less) so that reinforcement will only need to carry the loading resulting from the triangular above the opening?

I would think a mass concrete panel (or lightly reiforced panel) would act similar to a masonry panel in this situation

 

[WillisV]

arch action is not a material specific phenomena - so yes a concrete wall can arch just like a masonry one would.

 

[a2mfk]

Yep, Willis is right. There are a whole lot of 2000 year old roman aquaducts constructed out of unreinforced stone that attest to this fact. The key is to keep the arch in compression and I believe this is done by developing enough width on the legs of the arch to resist the horizontal thrust. Flying buttresses in cathedrals such as Notre Dame use the same theory.

I may have used the wrong verbiage but I'm not up on my arch design...

 

[paddingtongreen]

The arch is at a lower angle than with masonry, check out the load spread permitted in the concrete, under a baseplate of smaller area than the pier, then turn it upside down and you have your case.

Michael.
Timing has a lot to do with the outcome of a rain dance.

 

[csd72]

The critical factor for most arches is not the actual arch itseld but the capacity of the supports to resist the arching thrust.