APA Engineered Wodd Handbooks Episode 5 pot

STRUCTURAL GLUED LAMINATED TIMBER (GLULAM) 4.85 quired for most two-hinged arches. Reference 11, chap. 9 gives detailed description and design procedures for glued laminated timber arches. 4.7 DESIGN TABLES 4.7.1 Beams Introduction. Glued laminated timber beams are used in a wide range of appli- cations in both commercial and residential construction. The tables in this section provide recommended preliminary design loads for two of the most common glued laminated timber beam applications: roofs and floors. The recommendations apply to glued laminated timber beams meeting the requirements of ANSI A190.1. The tables included in this section include values for section properties and capacities and allowable loads for simple-span and cantilevered beams. The tables are based on an allowable bending stress of F b ϭ 2400 psi for both Douglas fir and southern pine. Section Properties and Design Capacities. Tables 4.23 and 4.29 provide section properties and design capacities for two commonly used species of glued laminated timber beams under dry-use conditions. Bending moment and shear capacities are based on a normal (10-year) duration of load. Dimensions shown are net sizes, and capacities are based on loading perpendicular to the wide faces of the laminations; that is, bending about the x–x axis of the beam as shown in Fig. 4.10. Final design should include a complete analysis, including bearing stresses and lateral stability. See Design Examples 1 and 4 in this section for examples of preliminary design using glued laminated timber beam section capacities from Tables 4.23 and 4.29. Allowable Loads for Simple-Span Glued Laminated Timber Beams. Tables 4.24, 4.25, 4.30, and 4.31 provide allowable loads for glued laminated timber beams used as simple span roof members in snow load areas (DOL factor ϭ 1.15) and for non- snow loads (DOL factor ϭ 1.25). Tables 4.26 and 4.32 provide similar information for floor members (DOL factor ϭ 1.25). The tables can be used to size such mem- bers for preliminary design. Final design should include a complete analysis, in- cluding bearing stresses and lateral stability. See Design Examples 2 and 3 in this section for examples of preliminary design using glued laminated timber beam load-span tables. Allowable Loads for Cantilevered Glued Laminated Timber Roof Beams. Tables 4.27, 4.28, 4.33, and 4.34 are for preliminary design of cantilevered roof beams. The tables are based on balanced (fully loaded) as well as unbalanced loading. They do not include deflection criteria limitations. Final designs should include deflection requirements per the applicable building code, in addition to the bending and shear strength assessments incorporated in these tables. Final design should include a complete analysis, including bearing stresses and lateral stability. A minimum roof slope of 1 ⁄ 4 in. per foot in addition to specified camber is recommended to help avoid ponding of water on the roof. The cantilever beam tables presented are applicable to balanced lay-ups, such as 24F-V8 for Douglas fir and 24F-V5 for southern pine, for three different systems. See Fig. 4.33 for details of the following cantilever systems: 4.86 CHAPTER FOUR SYSTEM 1 SYSTEM 2 SYSTEM 3 0.20L LL 0.25L0.25L LLL LLL 0.17L0.17L FIGURE 4.33 Typical cantilever beam systems. System 1 is a two-equal-span cantilever system with the cantilevered beam ex- tending past the center support by approximately 0.20 ϫ the span, or 0.20L. Its overall length is therefore 1.2L, and the suspended beam’s length is 0.8L. System 2 is a three-equal-span cantilever system, with each of the two outer cantilevered beams extending past the center support into the middle span by 0.25L. Their length is therefore 1.25L, and the interior suspended beam’s length is 0.5L. System 3 is also a three-equal-span cantilever system, but the two outer span beams are suspended from the interior, double cantilevered beam, which extends past its two supports by approximately 0.17L. Its length is 1.34L, and the suspended beams are 0.83L each. The following are additional notes that apply to Tables 4.27, 4.28, 4.33, and 4.34: 1. Span ϭ spacing of column supports for cantilevered beams. 2. Load-duration factor ϭ as noted. 3. Cantilevered beam lay-up ϭ balanced. 4. Deflection has not been considered. 5. Service condition ϭ dry. 6. Tabulated values represent total loads and have taken the dead weight of the beam into account (assumed 35 lb/ft 3 for Douglas fir and 36 lb/ft 3 for southern pine). Live load is assumed to be 0.6 ϫ total load for purposes of checking strength under full unbalanced live load. STRUCTURAL GLUED LAMINATED TIMBER (GLULAM) 4.87 7. Volume factor is included. 8. Light (unshaded) areas limited by bending strength; dark-shaded areas limited by shear strength. Design Examples Design Example 1: Low-Slope Roof Design Using Section Capacities Given: 24 ft span, 24 ft wide tributary area Live load ϭ 30 psf (snow); duration of load ϭ 1.15 Dead load ϭ 10 psf (actual) Allowable total load deflection ϭ L/180 Allowable live load deflection ϭ L/240 Use 24F Douglas fir glued laminated timber Then: Load, w ϭ (30 ϩ 10)(24) ϭ 960 lb/ft to glued laminated timber 22 wL 960 ϫ 24 Max. moment ϭϭ ϭ69,120 lb/ft 88 wL 960 ϫ 24 Max. shear ϭϭ ϭ11,520 lb 22 Design: From Table 4.23, try 5 1 ⁄ 8 ϫ 21 (weight ϭ 26 lb/ft) Total load ϭ 960 ϩ 26 ϭ 986 lb/ft From Eq. (4.1), volume factor ϭ 0.9330 Design moment capacity ϭ 75 338 ϫ 0.9330 ϫ 1.15 ϭ 80,834 lb-ft 986 69 120 ϫϭ70,992 lb-ft Ͻ 80,834 lb-ft—OK 960 Design shear capacity ϭ 17,220 ϫ 1.15 ϭ 19 803 lb (For shear design, neglect all loads within a distance from supports equal to the depth of the beam.) 44 5wL 5 ϫ 986 ϫ 24 ϫ 1728 Deflection, TL ϭϭ 6 384EI 384 ϫ 7119 ϫ 10 ϭ 1.03 in. ϭ L/279 Ͻ L/180—OK 30 ϫ 24 Deflection, LL ϭϭ1.03 ϭ 0.75 in. ϭ L/383 Ͻ L/240—OK 986 Design Example 2: Low-Slope Roof Design Using Load-Span Tables Given: 24 ft span, 24 ft wide tributary area Live load ϭ 30 psf (snow); duration of load ϭ 1.15 Dead load ϭ 10 psf (actual) 4.88 TABLE 4.23 SectionPropertiesandDesignCapacitiesforDouglasFirGlulam Click here for high resolution view of the table 4.89 TABLE 4.23 Section Properties and Design Capacities for Douglas Fir Glulam (Continued) 4.90 TABLE 4.24 Allowable Loads for Simple-Span Douglas Fir Glulam Roof Beams (lb/ft)—Non-snow Loads Click here for high resolution view of the table 4.91 TABLE 4.24 Allowable Loads for Simple-Span Douglas Fir Glulam Roof Beams (lb/ft)—Non-snow Loads (Continued) 4.92 TABLE 4.24 Allowable Loads for Simple-Span Douglas Fir Glulam Roof Beams (lb/ft)—Non-snow Loads (Continued) 4.93 TABLE 4.24 Allowable Loads for Simple-Span Douglas Fir Glulam Roof Beams (lb/ft)—Non-snow Loads (Continued) 4.94 TABLE 4.25 Allowable Loads for Simple-Span Douglas Fir Glulam Roof Beams (lb/ft)—Snow Loads Click here for high resolution view of the table [...]...TABLE 4. 25 Allowable Loads for Simple-Span Douglas Fir Glulam Roof Beams (lb / ft)—Snow Loads (Continued ) 4. 95 TABLE 4. 25 Allowable Loads for Simple-Span Douglas Fir Glulam Roof Beams (lb / ft)—Snow Loads (Continued ) 4.96 TABLE 4. 25 Allowable Loads for Simple-Span Douglas Fir Glulam Roof Beams (lb / ft)—Snow Loads (Continued... TABLE 4.28 Allowable Loads for Cantilevered Douglas Fir Glulam Roof Beams (lb / ft)—Snow Loads (Continued ) 4.1 05 Click here for high resolution view of the table TABLE 4.29 Section Properties and Design Capacities for Southern Pine Glulam 4.106 TABLE 4.29 Section Properties and Design Capacities for Southern Pine Glulam (Continued ) 4.107 Click here for high resolution view of the table TABLE 4.30... for Simple-Span Southern Pine Glulam Roof Beams (lb / ft)—Snow Loads (Continued ) 4.114 TABLE 4.31 Allowable Loads for Simple-Span Southern Pine Glulam Roof Beams (lb / ft)—Snow Loads (Continued ) 4.1 15 Click here for high resolution view of the table TABLE 4.32 Allowable Loads for Simple-Span Southern Pine Glulam Floor Beams (lb / ft) 4.116 TABLE 4.32 Allowable Loads for Simple-Span Southern Pine Glulam . shear ϭϭ ϭ11 ,52 0 lb 22 Design: From Table 4.23, try 5 1 ⁄ 8 ϫ 21 (weight ϭ 26 lb/ft) Total load ϭ 960 ϩ 26 ϭ 986 lb/ft From Eq. (4.1), volume factor ϭ 0.9330 Design moment capacity ϭ 75 338 ϫ 0.9330. and 24F-V5 for southern pine, for three different systems. See Fig. 4.33 for details of the following cantilever systems: 4.86 CHAPTER FOUR SYSTEM 1 SYSTEM 2 SYSTEM 3 0.20L LL 0.25L0.25L LLL LLL 0.17L0.17L FIGURE. extending past the center support into the middle span by 0.25L. Their length is therefore 1.25L, and the interior suspended beam’s length is 0.5L. System 3 is also a three-equal-span cantilever system,