Replies

1. 
   Guest_ | Mar 19, 2000 09:55pm | #1

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   Sounds like spreading, I'm afraid you're right. Can you post a picture so we can all see exactly what this thing looks like?

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   Guest_ | Mar 20, 2000 04:06am | #2

   *so are you saying the arches are 14' with an 11" rise?..describe the arches.... 2 bricks wide , spanning 14', with a rise of 11", how do they come off the spring line...is there an architect?...are you the mason?

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   Guest_ | Mar 20, 2000 05:45am | #3

   *Without actually seeing your project???? Think of your archways as separate bridges (as in the Bridge of Troubled Waters thread). Your arch stability is going to be only as good as the foundation supporting it at each end. It would appear that the columns in each corner are not rigid enough to resist the spreading action caused by good old gravity. Your arch is attempting to become a straight line (and succeeding).Your steel header is not stretching. First, check the wood framing connections. I suspect you have them securely fastened to the header so they are not spreading. That leaves the columns around the framing. The brick, from ground to cornice, or that part the arch bears on, is structural only in the sense that it really resists compression vertically, but if you have not installed lateral compression blocking to the framing where the horizontal factor of the load falls then you are sure to have movement, hence spreading. If your brick columns were plumb before the arches were built I'll almost bet they are not now. (The framing inside probably still is).Your solution??? Short of removing the brick and starting over you can hope that the gap in blocking or in the spacing in the brick in the columns has closed and the movement has stopped. Remove the cracked mortar and repoint. If your brick is just tied in to the interior framed column and you left an air gap you can expect the force of the spreading to attempt to close that entire gap at the top. How BIG is that gap??Am I anywhere close in diagnosis? Ralph

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   Guest_ | Mar 21, 2000 06:22pm | #5

   *LeighRalph sounds like he hit pretty solid. Just to go into arch theory alittle. The "flatness" of the arch does not affect it's STRENGTH. It does affect where the load goes. A half circle, or barrel arch effectively transfers all load directly down along the column. The flatter you go the more shear load you will develop, and consequently you need to compensate. In the case of a square structure, you have no ajoining wall to catch the shear and direct the load downward. You need ultra rigid columns. Maybe having a hollow core brick collumn with rebar extending from the foundation, and tied in with a header going around the perimeter. You could with a little head scratching and good forms and supports, conceal all the concrete behind the brick and pour as you go. But don't confuse flatness with strength. The flying buttresses of Notre Dame were designed to solve just the problem you describe. Transfer the shear load from internal arches to the ground below, without having to build a wall 20 feet thick.As far as repair, I am sorry to not have a very good idea. My experience is with tradtional masonry, and I would give you a solution far more expensive than Ralphs.Good luck, and always watch where your load is moving. I once heard that you can learn alot about load and arches by watching water pour off of sloped surfaces. If you can duplicate the angle where arch meets column, and run water off of it, you will get a graphic picture of where the load goes in a wall. In your case it sounds like it goes out into empty air. Keep trying,Scott Davis

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   Leigh_Morgan | Mar 21, 2000 06:22pm | #4

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   I'm a homebuilder in central texas. I am presently building a home with a portico. It is almost free standing, connected to the main structure only by a 5' long by 8'wide breezeway roof. The portico is wood frame constructed except for the headers which are 6" steel I beams. The overall dimensions are 17' x 17', with the headers centered and spanning 14'. There are identical openings on all sides. The steel beams are sized correctly for the load and are not sagging. My problem is in the brick. I have constructed 4 columns at the corners measuring approx. 24"x24". Between the columns span "eyebrow archways" They are 2 bricks wide and the central height of each is 11" taller than the sides. I have forgotten the exact radius. They are all identical. The archways do not support any structural weight. There are no courses of brick above the centers of the arches. They were constructed 2 weeks ago. The centers of all 4 of the arches have begun to sag ( approx. 1/4") there is no mortar cracking in the centers of the arches, but cracking has occurred in the columns near and above the intersections of the ends of the archways and the columns. this cracking is small at the bottom of the cracks and progressively larger at the tops. To me, this is indicative of the columns spreading under the pressure of the sagging archways. My questions are 1. Can this be repaired? If so, How? 2. If it is unreparable, how should I construct it next time so that I wont have this problem again? 3. Is reducing the radius sufficient to fix it? If so what is a good reccommended radius for this span?