Design Freres Mass Ply Lam to the NDS

Freres Engineered Wood (Freres Lumber Co., Lyons, Oregon) manufactures Mass Ply Lam (MPL), mass-timber beams and columns rip-cut from Mass Ply Panel in Douglas fir laminated veneer lumber. It is recognized under APA Product Report PR-L325. SPEC Toolbox designs the beams and columns to the NDS, using the report’s reference design values in allowable stress design.

The integration covers the Freres Mass Ply Lam, cut vertically from Mass Ply Panel and used as beams (joist or plank orientation) or columns.

• Grades F21, F21A, F19, F19A, F16, F16A and F10, in Douglas fir LVL.
• Thickness 2-1/16 to 24-1/2 in., width 1 to 72 in. and lengths up to 80 ft; the higher grades reach the greatest depths.
• Joist (edgewise) and plank orientations, and axial columns.

At a glance, in the US scope the Freres MPL supports:

• Beams and columns.
• Allowable stress design (ASD).
• Dry service (moisture content below 16 percent).

• A range of grades with high design values. From F21 (bending 2,800 psi, modulus of elasticity 2.1 x 10^6 psi) down to F10, in joist and plank orientations, with a depth factor for bending and a length factor for tension per the report.
• Very large sections and long members. Members reach 24-1/2 in. deep and 80 ft long, cut from Mass Ply Panel, for long-span beams and heavy columns.
• A veneer-based lam. MPL is rip-cut from Douglas fir LVL Mass Ply Panel rather than laminated from sawn boards, giving a dense, dimensionally stable member.
• Fire resistance to two hours. MPL may be designed for fire exposure up to 2 hours by calculation per NDS Chapter 16 and IBC Section 722.

The Freres MPL members are available across the SPEC Toolbox member-design modules, worked in ASD to the NDS:

• Timber beam and Timber column.

and in the connection modules:

• the screw connection module and the CLT floor-to-glulam beam connection.

Member behaviour is taken from the integrated database with the reference design values of PR-L325, including the equivalent specific gravity used for fastener design.

Design follows the ANSI/AWC NDS under the IBC and IRC. APA Product Report PR-L325 publishes ASD reference design values for the MPL beams and columns, in bending, modulus of elasticity, shear, compression perpendicular and parallel to grain, and tension, for grades F21 through F10 in joist and plank orientations. These are adjusted per NDS Section 8.3 (glued laminated timber), with a depth factor applied to bending and a length factor to tension as given in the report, and a repetitive-member increase where applicable. Connections are designed per NDS Chapter 12 using the report’s equivalent specific gravity and minimum nail geometry. The members are made from Douglas fir LVL and are for dry service (moisture content below 16 percent); fire resistance is determined by calculation per NDS Chapter 16, for up to 2 hours. The ASD reference values convert to LRFD strengths through the NDS format conversion where required.