A treatise on architecture and building construction . Every alternate pair ofvoussoirs should be tied together with galvanized-ironclamps doweled into the stones, as shown at/l 110. Centers.—In building an arch, it is carried upfrom both piers or abutments at the same time. Duringconstruction, the stones must be supported until the ring iscompleted. For this purpose, a framework, made of plankshaving one side cut to exactly fit the curve of the arch, isused. This framing, known as a center^ is supported onposts; it is usual to insert wedges between the center fra-ming and the posts supporting
A treatise on architecture and building construction . Every alternate pair ofvoussoirs should be tied together with galvanized-ironclamps doweled into the stones, as shown at/l 110. Centers.—In building an arch, it is carried upfrom both piers or abutments at the same time. Duringconstruction, the stones must be supported until the ring iscompleted. For this purpose, a framework, made of plankshaving one side cut to exactly fit the curve of the arch, isused. This framing, known as a center^ is supported onposts; it is usual to insert wedges between the center fra-ming and the posts supporting it, which, when the arch is 62 MASONRY. 8 completed and the mortar has set, are driven out gradually,so as to bring the load on the arch ring without shock. Thecenter should be strong enough to support the weight ofthe arch and a share of the wall above, as no weight should beput on the arch until the mortar in the joints has become hard. Ill, Fig. 62 represents a form of center suitable forarches of small span. At a are shown the bearers, which. Fig. 62. are cut out of 2-inch plank, to a radius about 1 inch lessthan that of the intrados of the arch. At c are indicatedpieces of plank, nailed at the crown of the center to spliceand stiffen it. Small bearing strips b, about 1 in. X 2 in. insection, are nailed to the curved pieces a. At d are thelongitudinal braces; at c are the plates under the center andon top of the posts; at/ are the wedges; and at g, theposts, which, if quite long, should be braced at the middleby struts. 8 MASONRY 63 113. For arches of considerable span, centers morestrongly built are necessary. Fig. 63 shows a good form ofconstruction. At a and b are represented the bearers, break-
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Keywords: ., bo, bookcentury1800, booksubjectarchitecture, booksubjectbuilding
