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Chapter 22 



experiment to develop a laminated oak beam product utilizing the grade and 

 species of oak available in Arkansas. He tested two-ply specimens made of red 

 and white oak 1- by 4-inch lumber classified in nine groups according to strength 

 reducing characteristics. Data so obtained were used to place laminae in core and 

 faces of the beams and predict beam mechanical properties. For 12-inch-deep 

 beams laminated at 16-percent moisture content with the grades of oak lumber 

 available, modulus of elasticity averaged 1,749,000 psi and modulus of rupture 

 4,894 psi with computed allowable extreme fiber stress in bending of 1 ,750 psi. 

 (See sec. 10-4 for species-average strength values for clear wood.) 



Gluing green oak. — In usual practice, wood to be glue-laminated is condi- 

 tioned to the moisture content it will attain in use — generally near 10 percent — 

 before it is planed just prior to glue application and lamination. For some 

 applications such as lamination of oak planks into crossties, however, it would 

 be useful to glue green wood into assemblies. In an effort to accomplish this, 

 Murphey et al. (1971) dried surfaces of green northern red oak lumber by 

 application of high voltage, air at 300°F, platens at 350°F, and infra-red lamps. 

 They found that hot air and platen drying produced highest joint strength when a 

 resorcinol adhesive was used. Urea, melamine, and casein adhesives either 

 failed or produced lower strength joints. Surface drying with hot air yielded 

 joints with higher shear strengths than did platen drying. 



Two-ply laminated hardwood lumber. — Suchsland (1980) proposed that 

 yields of hardwood furniture dimension lumber could be increased substantially 

 by manufacturing two-ply lumber. (See discussion related to figure 22-2.) He 

 concluded that there would be added processing costs due to lamination, but in 

 many ways manufacture would be simplified. In the sawmill, emphasis would 

 shift from quality recovery to volume recovery. Live sawing would be favored 

 and lumber grading could be simplified. The roughmill in which dimension parts 

 are manufactured could be more automated, since defects would not have to be 

 detected and removed. 



TRUCK TRAILER FLOORING^^ 



The U.S. Department of Commerce (1975) estimated that 191,262 truck 

 trailers were shipped from U.S. manufacturers in 1974. Of these, 127,460 units, 

 or 67 percent, were van-type trailers. Manufacturers estimated that approxi- 

 mately 90 percent of the van trailers, 115,600 units in 1974, incorporated 

 laminated or solid wood planking as the primary flooring material. The other ten 

 percent primarily were refrigerated units with extruded aluminum flooring. 

 Also, 36,834 platform or flatbed trailers, incorporating wood floors were 

 shipped in 1974. 



Total truck trailer shipments in 1979 numbered 209,522 units (U.S. Depart- 

 ment of Commerce 1980), an increase of 10 percent over 1974 levels; produc- 

 tion of van and platform trailers with wood floors therefore also increased, to 

 about 167,000 units. 



^^Text under this heading is taken, with minor editorial changes and permission of the authors, 

 from Fergus et al. (1977). 



