Building Design and Construction Handbook - Merritt - Ventech!

WOOD CONSTRUCTION 10.73
FIGURE 10.19 Bases for segmented wood arches: (a) and (b) tie rod
anchored to arch shoe; (c) hinge anchorage for large arch; (d) welded
arch shoe.
Arches are economical because of the ease of fabricating them and simplicity
of field erection. Field splice joints are minimized; generally there is only one
simple connection, at the crown (Fig. 10.20). Except for extremely long spans, they
are shipped in only two pieces. Erected, they need not be concealed by false ceilings,
as may be necessary with trusses. Inasmuch as arches have large cross sections,
they are classified as heavy-timber construction.
Changes in moisture content may be of great importance in three-hinged arches
that become horizontal, or nearly so, at the crest of the roof. Shrinkage, increasing
the relative end rotations may cause a depression at the crest and create drainage
problems. For such arches, therefore, consideration must be given to moisture content
of the member at the time of fabrication and in service, and to the change in
end angles that results from change in moisture content and shrinkage across the
grain.
A long-span arch may require a splice or moment connection to segment the
arch to facilitate transportation to the job site. Figure 10.21 shows typical moment
connections for wood arches. Moment connections should be located at the point
of minimum moment when possible.
(See K. F. Faherty and T. G. Williamson, ‘‘Wood Engineering and Construction
Handbook,’’ McGraw-Hill Publishing Company, New York, for additional information.)
10.24 TIMBER DECKING
Wood decking used for floor and roof construction may be sawn lumber with nominal
thickness of 2, 3, or 4 in or glued-laminated.