Design Mercer CLT to the NDS

Mercer (Mercer Mass Timber, Conway, Arkansas) manufactures cross-laminated timber. In the US it is recognized under APA Product Report PR-L347, rated to ANSI/APA PRG-320. SPEC Toolbox designs the panels to the NDS, in allowable stress design.

The integration covers Mercer CLT, cross-laminated Southern pine laminations, in visual and E-rated grades.

• Visual grades V3 and V3M1 (No. 2 Southern pine faces), and E-rated grades E4M1, E4M2, E4M3, E4M11 and E4M12 (from 2100f-1.8E to 2700f-2.2E MSR Southern pine).
• Layups from 105 to 315 (3 to 12-3/8 in. thick), including XL layups with doubled outer laminations; panels up to 12 ft wide and 60 ft long.
• Applications in floor, roof and wall panels.

At a glance, in the US scope the Mercer panels support:

• Load-bearing floors, roofs and walls.
• Allowable stress design (ASD).
• Dry service (average solid-sawn moisture content below 16 percent).

• Dense Southern pine, in visual and E-rated grades. Laminations are Southern pine (specific gravity 0.55 to 0.57), from the visual V3 grade up to the 2700f-2.2E E4M1 grade, giving high bending capacity and dowel-connection values.
• XL layups. Selected layups double the outer laminations to raise major-direction bending capacity for a given thickness.
• Large panels. Panels reach 12 ft wide and 60 ft long, up to 12-3/8 in. thick, for wide floor and roof plates with fewer joints.
• Fire resistance to two hours. Exposed panels may be designed for fire exposure up to 2 hours by calculation per NDS Chapter 16.

The Mercer panels are available across the SPEC Toolbox CLT modules, worked in ASD to the NDS:

• CLT floor, CLT wall and CLT shear wall.

and in the connection modules:

• the screw connection module and the panel-to-panel connection details (spline, butt joint and half-lap);
• CLT floor-to-glulam beam, CLT floor-to-floor and CLT wall-to-wall connections.

Panel behaviour is taken from the integrated database with the reference design values of PR-L347, using the grade specific gravity for fastener design.

Design follows the ANSI/AWC NDS under the IBC and IRC. APA Product Report PR-L347 publishes ASD reference design values for Mercer CLT, rated to ANSI/APA PRG-320: effective bending capacity, bending and shear stiffness, and shear, in the major and minor directions, for the Southern pine V-series and E-series grades. These are adjusted per NDS Table 10.3.1, without the lumber size factor, with a creep factor of 2.0 applied to long-term deflection; the report also prints single-span deflection equations that use the effective bending and shear rigidities. Connections are designed per NDS Chapter 12 using the grade specific gravity (0.55 to 0.57). The evaluation is for dry service (average solid-sawn moisture content below 16 percent); fire resistance is determined by calculation per NDS Chapter 16, for up to 2 hours.