I/EC
Materials of Construction
LAMINATED WOOD Modern plant construction uses an old material in a new form
by Charles W. Masterman, Rilco Engineered Wood Products Div., Weyerhaeuser
W ( new material
OULDN'T IT be
wonderful
if
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were discovered that would be strong, yet relatively light in weight, durable, a n d noncorrosive? Let's suppose t h a t this material does not shatter when struck and that it can absorb shock a n d temporary overloads that would crack or break other materials. And, let's suppose further that this material is readily available from a perpetually replenished source. If such a new product were developed it would be hailed as a " m i r a c l e material." Actually, this material already exists and has been in use for centuries. It is
Co.
wood! Because it is h u m a n n a t u r e to take for granted something that we see every day, let's take a new look at wood to see how technology has m a d e it practical and economical for use in chemical and industrial building construction. W h a t Is Laminated Wood?
I n the past, m a n h a d long d r e a m e d of gluing small pieces of wood together into larger pieces. It has been only in recent times, however, that structural glues a n d completely waterproof adhesives were de veloped, that produce a bond as strong or stronger than the wood.
L a m i n a t e d members are an as sembly of wood laminations, or plies, in which the grain of all laminations is parallel longitudinally. Glue laminating frees wood from limitations to size or shape. Any size can be produced—the only practical limitation being the maxi m u m dimensions that can be handled in transport. (These structural laminates are not to be confused with plywoods and veneers, m a d e by cross-grained bonding together of thin wood sheets). L a m i n a t e d m e m bers can take the form of flat or pitched beams, arches, or trusses. Manufacture of Laminated Members
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INDUSTRIAL AND ENGINEERING CHEMISTRY
W O O D vs. STEEL. Results of α fire test conducted at South west Research Institute in San Antonio, Tex., show comparison between unprotected w o o d joists and unprotected steel joists in buildings. At test's end steel supports had collapsed, while maximum deflection of w o o d was 0.5 inch. Source: National Lum ber Manufacturers Association.
Glued-laminated wood m e m b e r s are manufactured from stress graded, kiln-dried lumber of a structural species, such as West Coast Douglas Fir, a n d bonded with casein or phenol-rcsorcinol glues u n d e r a pres sure of over 100 p.s.i. Arches a n d curved members are fabricated by applying a uniform coating of glue to each ply. T h e plies are laid u p into curved forms according to a predetermined schedule so that material of highest strength will be placed in the m e m b e r at points of highest stress. T h e assembly of plies is then pulled into the form which has been set to a c u r v a t u r e that conforms with the shop drawings. It is clamped in this curved position and kept u n d e r
Laminated w o o d beams and columns were used in constructing Weyerhaeuser's chlorine plant at Longview, Wash.
pressure until the glue is properly cured. Having then permanently taken on the required shape, the member is now ready for final sur facing, fabrication, and finishing. Chemical Resistance
In the chemical industry, wood has long been used for pipe, vats, tanks, containers, and equipment in which chemicals are used. Wood's in herent resistance to many chemicals, such as mild acids and acidic salts, makes it a preferred material for plant construction, especially for buildings which house chemical proc esses and products. Because of its resistance to cor rosion, wood is often used in buildings that warehouse fertilizer, salt, and similar corrosive materials. The Summers Fertilizer Co.'s buildings at Seasport, Me., for instance, is constructed with radial arches pro duced by the Weyerhaeuser Co.'s Rilco Engineered Wood Products Division. The building is of clearspan construction to provide maxi mum utility of space. Another example is a huge 70,000ton capacity warehouse just com pleted by the Cayuga Rock Salt Co., Inc., of Myers, Ν. Υ. Constructed at about half the cost, and twice the speed of usual structures of this capacity, the roof is supported by Rilco tied arches which form four 50-foot bays. The building is 304 feet long. The Rilco arches are 34 feet above ground and are supported by pressure-creosoted poles. The 60,800 square foot inside floor area is of bituminous macadam. The building provides storage at a cost
of about $2 per ton, whereas any other method of construction would have cost double or more. Expensive maintenance, such as repeated scraping and painting of structural members, is eliminated by the use of laminated beams and columns in the construction of the Weyerhaeuser Co.'s chlorine plant located at Longview, Wash. The laminated wood roof beams in the 300 foot long building are 9 inches X 34x/g inches X 68 feet. The sup porting columns are 6 inches X 29V4 inches X 24 feet. Similar construction was em ployed in the Western Foundry Co.'s building at Tigard, Ore. This 21,000 square foot building has a roof supported by Rilco beams that are up to 11 X 24VS inches in section and 60 feet in length. Monson & Sivers, engineers for the building, report "Three basic shell systems were considered. Upon ana lyzing all three, the most econom ical was the glued laminated beam system. Cost of the basic laminated shell in its entirety, including the columns, roof and crane beams plus all the necessary bracing, erected, was slightly over $1 per square foot. In going to the laminated beam system, aesthetic qualities were not overlooked, as the clean lines of the beans and columns give somewhat of a classic appearance."
building to fight the fire. Un protected structural members of other materials can collapse without warning. The National Lumber Manu facturers Association has recently published a technical report en titled "Comparative Fire Test on Wood And Steel Joists." Two-roof systems, one of wood and one of exposed steel, were simultaneously exposed to equivalent fire conditions. Fire exposure followed the tempera tures of the standard time-tempera ture curve specified in American Society for Testing Materials, Des ignation E-119. After 12 minutes of the test, the panel supported by steel joists had deflected 18 inches which was the limit of the measuring device. The temperature at this time was about 1300°F. After the gas burner was cut off at 13 minutes, the deformation continued until the panel with steel joists collapsed. On the other hand, the panel with wood joists supported its full design load during the entire test, and the maxi mum deflection recorded was V2 inch. After the steel joists had col lapsed, the wood joists retained 80% of their section size and were still supporting their loads. A film made of this test is available from the Na tional Lumber Manufacturers As sociation, 1319 Eighteenth Street, N. W., Washington 6, D. C.
Fire Resistance
W o o d Has N u m e r o u s A d v a n t a g e s
Laminated wood structural mem bers, being of relatively large cross section, lose their strength only in proportion to the degree of charring. Penetration tests on wood exposed to standard fire temperatures show that wood chars at the rate of about 1 inch in depth in 33 minutes. This "slow-burning" advantage of wood enables firemen to safelv enter the
Wood is resistant to corrosive vapors, is readily available, and pos sesses fire resistance that is not often recognized by the general public. Wood, being a fibrous material, is less sensitive to repeated loads than are the more crystalline structural materials. Laminated wood mem bers are an engineered material that is designed for specific loads and span conditions. Before embarking on a new build ing program, it would certainly be well to take a fresh look at one of our oldest building materials—wood, made more adaptable than ever in its modern laminated form.
Storage building at C a y u g a Rock Salt Co., Ludlowville, Ν. Υ., is constructed with 1 5 6 laminated w o o d arches spanning 5 0 feet, spaced 8 feet a p a r t .
Our authors like to hear from readers. If you have questions or comments, or both, send them via The Editor, l/EC, 1155 16th Street N.W., Washington 6, D.C. Letters will be forwarded and answered promptly. VOL. 53, NO. 7
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JULY 1961
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