## 2 Materials and Methodology
### DCLT Panel Preparation  
A total of 1.8 m\({}^{3}\) (750 board feet) of ungraded, rough-sawn, random width, 31 mm thickness, 3 m length black locust boards were purchased from a sawmill in Newfield, NY. Also, a total of 24 NeLMA [14] finish grade, flat-sawn, eastern white pine boards with 22 mm thickness, 197 mm width, and 3.65 m length were purchased from a local lumber yard near Syracuse, NY. The eastern white pine boards had been kiln-dried and surfaced on four sides (S4S), but the black locust boards needed to be conditioned and surfaced (S4S) before fabrication. All the boards were then placed in an ambient temperature  
Figure 3: Apparent bending stiffness properties of two alternatives of hybrid DCLT panels with two species of white pine (WP) and black locust (BL). laboratory room to reach an equilibrium moisture content of approximately 12%. The average moisture content of the boards, determined with a Delmhorst (BD 2100) pin-type moisture meter, was measured as 11.8% at the time of fabricating the specimens. They were surfaced and planed to the desired thickness of 19 mm. Three replicates of each four-ply DCLT (\(\pm\)10\({}^{\circ}\), \(\pm\)20\({}^{\circ}\), \(\pm\)40\({}^{\circ}\), and 70\({}^{\circ}\)) and one four-ply CLT (DCLT 90\({}^{\circ}\)) panel were fabricated to final dimensions of 76 mm thick, 30 cm wide, and 2.74 m long. Figure 4 illustrates the dimensions and the orientation of the panels. The width-to-thickness ratio of all the diagonal DCLT panels in this study followed the standard recommendations of 4:1 to limit the impact of rolling shear [15]. The white pine boards (angle plies) were cut to the desired size from straight grain and defect-free sections, eliminating the possible effects of knots on the results. However, because of the NeLMA finish grade's small knots and the difficult process of cutting the boards in different grain orientations, as shown in Figure 5a, minimal numbers of small knots were included in some of the boards. Before panel assembly, the longitudinal modulus of elasticity (MoE) of each black locust board (individual outer layer) and three eastern white pine sample boards was measured using the flatwise measured deflection of a simply supported board under a non-destructive center-point loading. Figure 4: Dimensions and orientations of DCLT panels of the study. Figure 5: From top left, (**a**) cutting of boards to desired grain orientation (representative sample at 10\({}^{\circ}\)), (**b**,**c**) DCLT panel’s gluing process, and (**d**) DCLT panel’s pressing process. For panel fabrication, the boards were face-glued using Loctite HB X452 Purbond (Henkel Corporation, Bridgewater, NJ, USA) polyurethane adhesive with a recommended spread rate of 180 g/m\({}^{2}\) to glue the top and bottom of the lamina (face-glued) and without paying attention to the position of the board defects. The grain orientations of boards used in the inner layers were alternated in the second and third layers (Figure 4). The DCLT panels and the CLT panel clamping pressure was controlled by calibrated tightening torque set at 81.3 N.m (60 ft.lbf) per Equation (6) for torque-turn-tension control [16] to attain a minimum pressure of 410 kPa for 24 h, using a mechanical press and a pneumatic impact wrench. \[\rm T=K\times D\times F \tag{6}\]  
where T is the required torque energy, K is the nut factor (depending on characteristics of the nut), D is the nominal diameter, and F is the desired force value. The nut factor is a variable determined by the nut geometry, the friction in the threads, and the friction between the nut, washer(s), and sealing surface. In this case, friction values were initially assumed for the well-oiled interfaces, and the actual clamping force was confirmed by placing pressure-sensitive indicating film (Fujifilm Prescale(r) Sensor Products Inc. Madison, NJ, USA) between the pressing platen and the CLT beam face. The torque was applied until a specified \"threshold\" level was attained and an additional angle-of-turn was applied to finish the installation.