CASE STUDY OF 3-PLY COMMERCIAL SOUTHERN PINE CLT MECHANICAL PROPERTIES AND DESIGN VALUES

This work elucidates on a case study of industrially manufactured cross-laminated timber (CLT). Two methods are used to calculate specimens section modulus: Sgross and Seffective. The first assumes that specimens behave as a continuous material, whereas the second considers the cross laminations (shear analogy method). Although the shear analogy method is indicated for construction purposes, applications, such as trench shoring, matting, and work platforms, could benefit from a simpler calculation method. There- fore, theobjective of this work was to conduct a case study of Modulus of Rupture (MOR) and Modulus of Elasticity (MOE) of southern pine CLT to compare the previously mentioned calculation methods. Both parametric and nonparametric fifth percentiles and associated Fb values are reported and were substantially higher than those of the constituent lumber. For MOE, empirical testing and calculation based on gross moment of inertia provided lower values as compared with the constituent lumber

USING NONDESTRUCTIVE TESTING TO IDENTIFY PREMIUM GRADES IN SOUTHERN PINE AND DOUGLAS-FIR UTILITY CROSSARMS

Unlike lumber, wood utility crossarms are not currently available in premium grades that indicate a higher level of performance in service.  Previous research has shown that nondestructive testing (NDT) techniques are able to predict performance properties of solid wood products with considerable accuracy. The aim of this study was to determine the suitability of NDT methods for predicting the stiffness and strength properties of wood utility crossarms and possibly aiding in the identification of a premium grade that exhibits higher average performance values. Samples of Douglas-fir and southern pine were subjected to multiple NDT technologies to estimate modulus of elasticity (MOE).  Each specimen was also measured for MOE and modulus of rupture (MOR) with a static bending test.  Bivariate correlations and corresponding R2 values showed that Fibre-gen’s Director HM200 and Metriguard’s E-computer were the most accurate NDT devices among those tested for predicting both MOR and MOE.  Means tests also suggested that the devices could possibly be used to identify a premium grade that shows significantly higher average performance values

Use of Longitudinal Vibration and Visual Characteristics to Predict Mechanical Properties of No. 2 Southern Pine 2 × 8 and 2 × 10 Lumber

The objective of this study was to evaluate the accuracy of single MOE and MOR and combined mechanical properties with visual characteristics to improve the prediction of 2 x 8 and 2 x 10 No. @ southern pine lumber. This study evaluated the following variables: nondestructive tests, knots (knot diameter ratio [KDR] and knot area ratio), density, and mechanical properties (stiffness [MOE] and strength [MOR]). A total of 486 pieces were used, and linear regression models were constructed using stepwise selects to determine the best variables to estimate the MOE and MOR of southern pine lumber. The best single predictor for MOE and MOR was dynamic MOE (dMOE) followed by density. Among the two knot measurement methods used, the KDR best predicted stiffness and strength. For predicting the MOE, the variables dMOE, density, and KDR. The results showed that the addition of knot measurements to the models is able to improve the prediction of mechanical properties

THE INFLUENCE OF FOAM DISCONTINUITY IN THE SHEAR ZONE OF STRUCTURAL INSULATED PANEL BEAMS

The effect of foam discontinuity in the shear zone of structural insulated panel (SIP) beams was investigated in the current research. Two depths of 15.24 cm and 31.11 cm (6.5 in and 12.25 in) (SIPs) were evaluated in 1/3-point bending. Panels were sawn into beams, each approximately 29.84 cm (11.75 in.) wide, for mechanical testing. Half of the panels had joints or discontinuities in the foam layer in a location that was subject to shear stress during the bending tests. Half of the panels had joints or discontinuities in the foam layer in a location that was subject to shear stress during the bending tests. Half of the panels did not have joints or discontinuities in the foam layer in the locations that were subject to shear stress during the bending tests. The specimens with no foam discontinuity, stressed in shear, were approximately twice as strong as the specimens with a foam discontinuity. This finding has implications for routine testing and evaluation as well as for allowable properties. In the case of routine testing, foam discontinuities should purposefully be located in the zone of maximum shear as these appear to be a limiting factor. In cases where a producer manufactures SIPs with zero discontinuities, it may be prudent to seek premium value as those panels would achieve superior properties. Keywords: Structural insulated panels (SIPs), shear stress, bending test, foam, joints and routine testing.

Bowtie Beams: Novel Engineered Structural Beams from Southern Pine Lumber

The intersection of decreasing resources and increasing population and its associated demands creates a need to develop alternative products to solid sawn lumber. This research used a modified form of sawn southern pine (SP) lumber in which cants were sawn into symmetrical double-trapezoidal shapes and glued together to form a bowtie beam. The result was a cross-sectional shape that was widest at the beam flanges and narrowest at the neutral axis. Cants were cut from logs and sawn into trapezoids, nondestructively tested, glued into the bowtie beams, and nondestructively and destructively tested to determine mechanical values as per ASTM D4761. The objectives of this study were to manufacture composite bowtie beams and to conduct nondestructive and destructive testing on the beams. Overall, the bowtie beams compared favorably with strength properties of No. 2 SP lumber of roughly equivalent size to the bowtie beams. The bowtie beam shows promise as an engineered product because a minimal amount of capital and technology is needed to process small-diameter trees into this value-added product

Rapid Assessment of Southern Pine Decayed by G. Trabeum by Near Infrared Spectra Collected from the Radial Surface

The use of near infrared (NIR) spectroscopy for predicting levels of degradation in southern pine (Pinus spp.) by Gloeophyllum trabeum for periods over 1-8 da was investigated. NIR spectra collected from the center of the radial face of each sample after laboratory soil block decay tests were used to develop calibrations. Calibrations were developed for mass loss, compression strength, and exposure period using data measured from prior methods and untreated and mathematically treated (multiplicative scatter correction and first and second derivative) NIR spectra from various ranges of wavelengths by partial least squares regression. Strong relationships were derived from the calibrations with the strongest R2 values of 0.97 (exposure period), 0.94 (compression strength), and 0.91 (mass loss). Calibrations for exposure period showed the strongest statistics for predicting wood decay of the validation test set (R2 = 0.92; RPDp [ratio of the standard deviation of the measured data to the standard error of prediction] = 3.95 [first derivative, 1100-2250 nm]), while predictions for mass loss of the decayed samples resulted in R2 = 0.86 and an RPDp = 3.17 (multiplicative scatter correction, 1100-2500 nm), and the strongest compression strength prediction resulted in R2 = 0.76 and an RPDp = 2.50 (second derivative, 1100-2500 nm). These results suggest that NIR spectroscopy can adequately predict wood decay from spectra collected from the radial face of southern pine

COMPARISON OF NONDESTRUCTIVE TESTING METHODS FOR EVALUATING NO. 2 SOUTHERN PINE LUMBER: PART A, MODULUS OF ELASTICITY

Modulus of elasticity (MOE, or E) is one of the main quality indicators in structural lumber stress grading systems. Due to a relatively high amount of variability in contemporary sawn lumber, it is important that nondestructive evaluation technology be utilized to better discern high-E-value pieces from low-E-value pieces. The research described in this study is from a laboratory test of three nondestructive technologies applied to 343 pieces of visually graded No. 2 southern pine lumber collected across the southeast region of the United States. The evaluated technologies included continuous lumber test in continuous proof bending (Metriguard Model 7200 High Capacity Lumber Tester), transverse vibration (Metriguard E-Computer), and two stress wave tools (Falcon A-Grader and Carter Holt Harvey Director HM200). For each of the nondestructive techniques, results were compared with static E as determined by the four-point static bending tests following ASTM D198-14. In all cases, the nondestructive techniques successfully predicted E for all lumber sizes, with linear regression r2 values ranging from 0.77 to 0.86

Assessing Southern Pine 2x4 and 2x6 Lumber Quality: Longitudinal and Transverse Vibration

A primary goal of structural lumber grading is the identification of the strength-reducing characteristics that impact the modulus of rupture (MOR). Non-destructive evaluation technology can be used to identify material of greater stiffness. This study investigates the use of longitudinal and transverse vibration methods to evaluate the mechanical properties of 2x4 and 2x6 southern yellow pine lumber. A total of 1240 samples were conditioned to 12% equilibrium moisture content. All samples were first non-destructive tested using transverse vibration equipment (Metriguard E-computer) in edgewise and flatwise directions and three different longitudinal vibration devices (Fakopp Portable Lumber Grader, Director HM200, and Falcon A-grader) to obtain the vibration properties using transverse and longitudinal methods. The dynamic modulus of elasticity (MOE) of each sample was calculated based on the fundamental wave equation.  Static bending was subsequently conducted according to ASTM 198 (2012), and the rate of loading followed ASTM D4761 (ASTM 2012). The results showed statistically significant correlations between static MOE and the dynamic MOE measured by non-destructive techniques. Weaker correlations were found between MOR and the dynamic MOE values. Likely this finding is because it is related to the ultimate strength of material, often associated with the existence of localized defects, such as a knot, on the lumber piece. This study indicates that non-destructive techniques can potentially be used to evaluate 2x4 and 2x6 stiffness and improvements can be done for a better evaluation of southern pine lumber

FIELD TEST OF A NOVEL NON-DESTRUCTIVE TESTING DEVICE ON WOOD DISTRIBUTION POLES

A field test was performed on 50 utility poles that had been removed from service. The poles were non-destructively tested with a novel device, the PoleXpert. The poles were then destructively tested. Results indicated that the device’s output correlated well with the actual bending strength of the poles. As such it appears that the device has potential to identify weak or structurally compromised poles. Seventeen (17) of the poles were reinstalled in the ground and tested. The remainder 33 poles were tested horizontally in a pole-testing fixture. The device demonstrated positive correlation in both situations