Our latest design challenge is a brick arch with recessed accent courses that tie in to the recessed accent courses of the running bond of the building. Here is a building in Baltimore with a similar style arch.
What complicates the matter further is the 32" soffitt and the question of how we will prefabricate the arch. When designing a normal radial brick arch the measurements that we need to determine are the circumference, angle, length of the outside arc, and brick size.
circumference x angle = length
360
But in this case the masonry opening arc is half round and the outside arc is elliptical. Also we are limited by the size of brick because the joints of the accent course must line up with the running bond. Here is where it gets tricky. Instead of starting with the arch, I started with the running bond and accent course, and started at the top of the arch. To pass the eye test the arch cannot be too tall in the center, but also the 2 1/4" brick size must line up to the same number of courses in the arch. The only way to get the desired effect was to start with 3 5/8" closure size brick towards the top of the arch, then work our way smaller towards the bottom. This is how we came up with the ellipse.
I am no math wiz, so if anyone knows a better way to reverse engineer this thing send me a message. What has me mixed up is the length of the elliptical arc combined with the size limit of the radial segments.
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