Bending properties of a novel engineered composite from southern pine lumber

Abstract

This paper presents the results of a study in which novel engineered composite lumber was developed, manufactured and tested. The engineered composite lumber was made by edge-laminating lower-grade No. 3 solid-sawn southern pine (SP) lumber with higher-grade tension chord material to yield tension chord lumber (TCL). Three groups of TCL (38 mm × 235 mm × 4.9 m) were made with varying combinations of SP lumber including machine stress rated (MSR) 2400Fb-2.0E, MSR 2400Fb-2.0E finger joint, and visually graded No. 1 finger joint material. One group of visually graded No. 3 control lumber (38 mm × 184 mm × 4.9 m) was also tested. All specimens were tested in static four-point bending on a universal testing machine. The modulus of elasticity (MOE) and modulus of rupture (MOR) were determined. The TCL lumber had significantly greater MOE values as compared with the control lumber. The mean MOE values of TCL ranged from 12.4 to 12.6 GPa, as compared with 9.6 GPa for the control group. The mean MOR values of TCL ranged from 39.3 to 47.6 MPa, as compared with 35.9 MPa for the control group. Perhaps most importantly, the 5th percentile values of MOR of the TCL were approximately double those of the control group, 29.1, 27.0, and 27.4 MPa versus 11.8 MPa, respectively.