Virtually any species of wood can be used in the laminating process if the design values have been determined. Different species can be intermixed within the depth of a section to achieve optimum resource utilization. Higher-strength species are positioned in a beam in zones that will be subjected to high stresses under design loads. Lower-strength species can be placed in zones with lower in-service stresses. Similarly, manufacturer of glulam beams can be based on a graded layup concept. This requires that laminations with a higher lumber grading be used in zones subjected to high design stresses, and lower grades, in lower-stressed areas of the member. As a consequence, glulam members are a resource-efficient wood product, since varying grades and species can be used to achieve desired performance. Constant-depth members normally are a multiple of the thickness of the lamination stock used. Variable-depth members, because of tapering or special assembly techniques, may not be exact multiples of these lamination thicknesses. Nominal width of stock, in 4 6 8 10 12 Standard member finished width, in 3 or 31/8 5 or 51/8 63/4 81/2 or 83/4 101/2 or 103/4 Standard widths as listed above are most economical, since they represent the maximum width of board normally obtained from the stock used in laminating. Other widths, such as 31/2 or 51/2 in, which fit well with conventional 2  4 and 2  6 framing, are also available in many market areas. FIGURE 10.28 Finger joints: (a) fingers formed by cuts perpendicular to the wide faces of the boards; (b) fingers formed by cuts perpendicular to the edges. When members wider than the stock available are required, laminations may consist of two boards side by side. These edge joints must be staggered, vertically in horizontally laminated beams (load acting normal to wide faces of laminations), and horizontally in vertically laminated beams (load acting normal to the edge of laminations). In horizontally laminated beams, edge joints need not be edge-glued. Edge gluing is required in vertically laminated beams. Edge and face gluings are the simplest to make, end gluings the most difficult. FIGURE 10.27 Plane sloping scarf. Although no longer used in the glulam industry, a plane sloping scarf (Fig. 10.27), in which the tapered surfaces of laminations are glued together, can develop 85 to 90% of the strength of an unscarfed, clear, straight-grained control specimen. Finger joints (Fig. 10.28) are less wasteful of lumber and hence are widely used by the glulam industry. Quality can be adequately controlled in machine cutting and in high-frequency gluing. A combination of thin tip, flat slope on the side of the individual fingers, and a narrow pitch is desired. The length of fingers should be kept short for savings of lumber, but long for maximum strength. Typical finger joint lengths are 1
11/4
. The usefulness of structural glued-laminated timbers is determined by the lumber used and glue joint produced. Certain combinations of adhesive, treatment, and wood species do not produce the same quality of glue bond as other combinations, although the same gluing procedures are used. Thus, a combination must be supported by adequate experience with a laminators gluing procedure. The only adhesives currently recommended for wet-use and preservative-treated lumber, whether gluing is done before or after treatment, are resorcinol and phenolresorcinol resins. Melamine and melamine-urea blends are also used for highfrequency curing of end joints. Glued joints may be cured with heat by several methods. Radio-frequency (RF) curing of glue lines is used for end joints and for limited-size members where there are repetitive gluings of the same cross section. Low-voltage resistance heating, where current is passed through a strip of metal to raise the temperature of a glue line, formerly was used for attaching thin facing pieces. The metal could be left in the glue line as an integral part of the completed member. Printed electric circuits, in conjunction with adhesive films, and adhesive films impregnated on paper or on each side of a metal conductor placed in the glue line are other alternatives. Preheating the wood to ensure reactivity of the applied adhesive has limited application in structural laminating. The method requires adhesive application as a wet or dry film simultaneously to all laminations, and then rapid handling of multiple

in constant evolution. The author prefers to use ST connectors for all connections except to network gear and the network patch panel which must be coordinated with the network gear manufacturer. Initially, ST connectors were popular with the manufacturers, then SC connectors saw an increase in use. Presently, the MTRJ and the LC connectors are becoming popular; both are excellent connectors. Patch cables, with different connectors on the ends, are available if needed. Occasionally IT people like to use different connectors to organize or classify their systems and equipment. The Commercial Building Telecommunications Cabling Standard, ANSI/TIA/EIA- 568-A, defines categories for 100-
unshielded, twisted-pair cables. The Category FIGURE 18.14 Lucent LC fiberoptic connectors. (Copyright
1999, Lucent Technologies, used by permission.) 3 designation applies to cables and hardware up to 16 MHz (16 Mbs). The Category 4 designation applies to cables and hardware up to 20 MHz (20 Mbs). The Category 5 designation applies to cables and hardware up to 100 MHz (100 Mbs). The Category 5e designation applies to cables and hardware over 100 MHz (over 250 Mbs). The Category 6 designation applies to cables and hardware over 250 MHz (over 500 Mbs). Practically speaking, CAT 3 cable is used for high-pair count outdoor and high-pair count backbone voice cable, and occasionally for station cable (from the closet to the phone). CAT 4 cable is nonexistent, at 20 MHz it is too close to CAT 3 to warrant manufacture. CAT 5 cable is used for low-end data installations and voice cable. CAT 5e, where e stands for enhanced, and CAT 6 are not ANSI/TIA/EIA standards at this writing, so it is necessary to look at the cable and system specifications and test results to determine performance. Most new installations should be CAT 5e or CAT 6 for economic reasons. One of the differences between CAT 5e and CAT 6 will be that the patch cable will be required to be CAT 6 and coordinated with the system. Using CAT 5e or CAT 6 for new installations is good for the industry, because currently there are many poor patch cables in use choking the speed of PCs. Horizontal cabling generally refers to cabling run from the communications closet to the workstation. A link specifically refers to the workstation outlet, the horizontal cabling, and the communications closet patch panel. A channel specifically refers to the cabling from the PC to the communications closet network gear, including all of the patch cables and the patch-panel connectors. Standard channel and link performance warranties are offered by the manufacturers for 15 years. Where the cable and jacks are made by different manufacturers, the jack manufacturer administers the warranty. It is extremely important to match the two manufacturers. Warranties are also available from some manufacturers for the entire cabling plant; i.e., for channels, backbone cabling, and campus cabling, including the fiberoptics. One of the problems with not coordinating cable and jack manufacturers happens over timethe connections at the jack become slightly loose and the network speed degrades until re-terminating the entire system becomes the best option. A 15-year warranty is preferred. FIGURE 18.15 Lucent non-plenum CAT 5 power sum, four-pair cable. (Copyright
1999, Lucent Technologies, used by permission.) FIGURE 18.16 Lucent CAT 5 power sum, 25- pair cable. (Copyright
1999, Lucent Technologies, used by permission.) It is important to note the economic advantage of using a Category 6 solution. To implement Gigabit Ethernet on CAT 6, the network electronics will use two pairs of the cable to transmit 500 Mbps and two pairs to receive 500 Mbps. To implement Gigabit Ethernet on CAT 5e requires all four pairs to transmit and receive 250 Mbps. The network gear and the network interface cards (NICs) in the PC are much more expensive for the CAT 5e solution. The only difficulty is that the cabling is usually in the construction budget, and the electronics are in the IT

For situations where greater diaphragm capacities are necessary and framing with a nominal thickness of 3 or 4 in is available, diaphragms may be constructed using heavier nailing schedules, such as that given in the Uniform Building Code. (Diaphragms, APAThe Engineered Wood Association, Tacoma, Wash.) Nails, staples, spikes, wood screws, bolts, and timber connectors, such as shear plates and split rings, are used for connections in wood construction. Because determination of stress distribution in connections made with wood and metal is complicated, information for design of joints has been developed from tests and experience. The data indicate that design values and methods of design for mechanical connections are applicable to both solid sawn lumber and laminated members. The National Design Specification for Wood Construction, (NDS) American Forest & Paper Association, provides design equations and tabulates design values for connections made with various types of fasteners. Design values for connections made with more than one type of fastener, however, should be based on tests or