Brick Arch
Brick Arch
(OP)
I am building a home, and have a brick arch over an entry way. Due to a mistake, the arch is wider and flatter than originally intended. I don't have any experience with masonry, and was looking for some guidance on how to confirm that this arch is adequate to support the weight of the brick and stone above it? Here is a picture:
http://www.mecaenterprises.com/downloads/arch.jpg
http://www.mecaenterprises.com/downloads/arch.jpg






RE: Brick Arch
RE: Brick Arch
RE: Brick Arch
Hokie66, what are my options, to tear it out and start over?
RE: Brick Arch
Dik
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It is the only solution I can think of appart of satisfying yourself that the arch is stable. It would be very messy but easier than tearing it down
RE: Brick Arch
RE: Brick Arch
If the appearance is also a concern, you would have to rebuild the brick arch.
BA
RE: Brick Arch
I have no experience with brick work, can anyone comment on whether the arch "Looks" like it is adequate? I'm just asking for a gut feel based upon your experience, on whether the arch looks like it is adequate to support the weight.
Thanks,
RE: Brick Arch
RE: Brick Arch
You may get some useful information on this link:
http://www.gobrick.com/BIA/technotes/t31.htm
BA
RE: Brick Arch
http://www.gobrick.com/bia/technotes/t31a.htm
RE: Brick Arch
He is extremely knowledgable about these matters.
RE: Brick Arch
RE: Brick Arch
One solution: Add two 1/4 or 3/8 plates, one on each side of the brick - say 8" to 12" wide by 30 inch long. Clamp the clamps with rods through the arch with 4 bolts, 6 would be too many, to hold the sides of the structure together against the splitting effect of the masonry above the not-arched-arch.
The plates won't be obnoxiously visible from the street side, and the rods will be invisible since they pass behind the facia.
An arched plate under the brick won't help much because the problem is the tendency of the bricks above the arch to split apart the ends of the arch, and it's the splitting side load (not the vertical load itself) at the ends of the arch that appear to be too much to be resisted by the sides.
RE: Brick Arch
To analyze your flat arch, I would add all the load above the arch, take half of it to each side. That is your vertical reaction. Find the angle of the arch at the jamb, divide the vertical reaction by the tangent of the angle, you have the horizontal reaction. As you will see, the horizontal reaction for a flat arch far exceeds the vertical reaction. That is the problem you have with your structure. From the picture, I can't tell for sure how the jambs are built, but if they are unreinforced masonry, there is no chance the jambs can resist the horizontal force.
RE: Brick Arch
http://www.gobrick.com/html/frmset_thnt.htm
RE: Brick Arch
I've attempted to wade through some of the recommendations given by all of you, but the results vary quite a bit. I've estimated the thrust to be anywhere from 3,000 lbs to 8,000 lbs.
Wanting to understand the loading better, I made a simple finite element model using plate elements in StaadPro. The results are shown at the link below. According to this analysis, the thrust is only about 1,600 lbs. I'm assuming it is a concrete slab 6" thk above the arch and 18" in the columns (they are actually 18"x18" solid columns). I don't design concrete, and so I may be making some ignorant assumptions. Accoring to this analysis, the maximum von mises stress is about 50 psi. Seems like a very low number, but I know mortar is not good in tension.
http:
Any thoughts on whether this analysis indicates I have a problem? I guess I'm wondering if I do have a problem, why it's standing today.
RE: Brick Arch
Your analysis indicates a vertical load of 6500# at each column and a tie force of 1600#. If the angle of struts is assumed to be about 60 degrees from horizontal, the tie force must be about 6500/tan(60) = 3750#. I don't know how it could be as low as 1600#.
You say the masons used no steel at all in the wall above the arch. Is it possible they used ladder type wire reinforcement every few courses of brick? It would not require much steel to resist 3750# tension.
Whatever they did, the arch seems to be holding the load to date. Whether it will continue to do so is the question we can't answer.
BA
RE: Brick Arch
http:
If I model as an arched beam with total of 7,000 lbs uniformly distributed, then I get a thrust of aobut 8,000 lbs. I'm wondering if the difference is that the FEA is treating the entire wall as a continuous slab which can transfer shear stresses internally, while the beam model assumes that it's all dead weight that is 100% resisted by the "arch" beam.
BARetired, I was told no steel was used; however, the guys that did the work speak no English and so I have not been able to get a definitive answer.
RE: Brick Arch
With a vertical reaction of 3500#, the truss and tie model would predict a tie force of about 2020#. Whether it is 1300 or 2020, you need some tensile capacity (very nominal) to handle it. If there is no steel, the masonry must be carrying some tensile stress.
The exterior face appears to be stone. Is it a veneer and if so, what is behind it? A stud wall? Can you draw a cross section through it?
BA
RE: Brick Arch
Is there two planes, one at the entrance door and other at windows upstair the entrance door?
The wall at the window upstair is supported on a slab or is it over the door wall?
What are the door-window wall materials?
What are the material arch?
What are the materials of the two wall beside the entrance door?
Could you submit some skecthes of these?
I could try to help if there is some time left to make desition.
Additional information:
I have seen tension rod on some building to void the horizontal forces, it is not so pretty but it is work. For the finishing if the fachade have to use some kind of painting that seems like the rod is rusty.
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While the stresses around window look reasonable, I don't quite understand why the stresses 1/3 way from the ridge under the slant roof are almost having the same intensity as under the arch (or as stress in the columns). Maybe it is due to losing some rigidity at the wall-eave joints (in pink color).
Just courious.
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BA
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RE: Brick Arch