APA Residential & Commercial - Page 16

Camber is curvature built into a fabricated member (see Figure 1 below) which is opposite in direction and magnitude to the calculated deflection which will occur under gravity loads.

The glulam industry recommends that roof beams be cambered or 1-1/2 items the calculate dead load deflection. This will generally be sufficient to assure that the beam will not exhibit a sag over a period of many years of loading, as may occur with non-cambered wood products. To achieve a level profile it is recommended that floor beams be only cambered of 1.0 times the calculated dead load deflection.

Camber for glulam beams is specified as either "inches of camber" or as a radius of curvature that is to be used in the manufacturing process. Commonly used curvature radii for commercial applications are 1,600 and 2,000 feet although any camber may be specified.

Most residential applications require very little or no camber which, in turn, makes glulam the ideal choice. stock beams are typically supplied with a relatively flat camber radius of 3,500 feet as shown in Table 5, or zero camber.

1. Indicates structural use: B-Simple span bending member, C-Compression member. T-Tension member. CB-Continuous or cantilevered span bending member.
2. Mill number.
3. Identification of ANSI Standard A190.1, Structural Glued Laminated Timber. ANSI a190. 1 is the American National standard for glulam beams,
4. Applicable laminating specification.
5. Western woods (see note 6).
6. Structural grade designation. The APA EWS 24F-1.8E designation is a glulam grade commonly used in residential applications.Combining a group of six layup combinations made with Douglas fir-larch, spruce-pine-if, southern pine, and /or hem-fir, this grade provides strength (allowable bending stress of 2,400 psi and allowable shear stress of  155 psi) and stiffness (modulus of elasticity of 1.8 x 106 psi) needed for typical residential applications, while greatly simplifying the design specification.
7. designation of appearance grade. INDUSTRIAL, ARCHITECTURAL, PREMIUM, or FRAMING.

Thus, they have just the right camber of residential construction. If, however, more camber is required, such as for a long span roof beam, custom beams are available through manufactures to meet the most exacting specifications.

For additional information on cambering glulam beams, refer to Engineered Wood Systems Technical Note: Glulam Beam Camber, Form EWS S550, which provides a camber table for various beam spans and radii of curvature.

Trademarks and Acceptances

Glulam beams manufactured by Engineered Wood Systems member are certified with the APA EWS trademark. The mark (as shown) signifies that the manufacture is committed to a rigorous program of quality verification and testing and that products are manufactured in conformance with ANSI Standard A190.1-92, American National Standard for Structural Glued Laminated Timber.

Typical information included in an APA EWS trademark is shown on the sample;e trademark. This information may vary depending on whether the member is supplied as a custom or stock product.

The APA EWS trademark is recognized by all major model building codes of the certification of glued laminated timber produced by Engineered Wood Systems members.