Spruce Pine Fir Research Articles

Rigidity coefficients of rubber belts for dynamic testing of modulus of elasticity and shear modulus of non-wood engineered board

To determine the appropriate stiffness coefficient k values for rubber belts used in dynamic testing of the elastic modulus and shear modulus of timber and solid wood composite materials, this study employed three different thicknesses of rubber belts. Dynamic tests were conducted on straw boards, Laminated Veneer Lumber (LVL), and Spruce-Pine-Fir (SPF) materials, and the results were validated and analyzed using static four-point bending tests. The conclusions drawn from this research indicate that the range of stiffness coefficient k values for the rubber belts obtained through dynamic testing fell between 0.05 and 0.28 N/m. The correctness of the dynamic testing method was verified through static four-point bending tests. The error levels for elastic modulus E and shear modulus G of the same type of board measured using the three different rubber belts were below 9.5% and 9.8%, respectively.

Performance of structural insulation panels under eccentric axial and racking loads with varying opening ratios

Structural insulation panels, which are actively applied in the housing market in North America and Europe by utilizing wood, an eco-friendly material, as the main material, are composed of OSB (Oriented Strand Board), EPS (Expanded Polystyrene), and SPF (Spruce-Pine-Fir), which is used as a connection between the panels. Structural insulated panels are used as a load-bearing wall to resist external forces without installing separate columns. The production of structural insulation panels consists of applying adhesive to both sides of EPS, which acts as an insulation material, and pressing wood boards (OSB), which exert strength as a structural material. The OSB on the outside resists compressive and tensile forces, while the EPS on the inside resists shear forces. The joints and openings of the structural insulation panels are reinforced with SPF (Spruce-Pine-Fir) structural wood. When structural insulated panels are used as an exterior wall structure, the installation of openings is essential. Based on the opening size that is popularly used in wooden structures, the performance evaluation of structural insulation panels under eccentric axial load and repeated lateral load due to the reduction of the cross-sectional area by installing the opening was carried out, and the behavior analysis through variable analysis and comparison analysis with the design equation was carried out.

Comparative experimental investigation on mechanical properties of bamboo scrimber and SPF

This paper presents a comparative experimental investigation of the mechanical properties for bamboo scrimber and spruce-pine-fir (SPF) clear specimens. The primary mechanical properties that were measured and compared included the strengths and moduli in bending, tension, compression, and shear, as well as the Poisson's ratios. The stress–strain curves and failure modes were also presented and compared. The experimental results demonstrated that, for the same category of strength and modulus, bamboo scrimber exhibited values approximately 0.5–5.5 times and 1.2–10.4 times higher than those of SPF, respectively. Bamboo scrimber specimens exhibited greater deformation at the ultimate states compared to SPF specimens. Furthermore, based on the bootstrap method, the characteristic values of the strengths and moduli for both bamboo scrimber and SPF in bending, tension, compression, and shear were determined. The results presented in this paper provide a clearer and more direct comparison of the mechanical property differences between bamboo scrimber and SPF, offering a fundamental reference for theoretical calculations and finite element simulations involving structures made from bamboo scrimber, SPF, and their composites.

Evaluation of Major Physical and Mechanical Properties of Trembling Aspen Lumber.

Trembling aspen (Populus tremuloides) is one of the major species within Populus, a predominant genus of hardwoods in North America. However, its utilization has been limited to pulp and paper or wood-based composite boards. This study aimed at evaluating the major physical and mechanical properties of trembling aspen lumber, with an ultimate objective of using this species to produce engineered wood products (EWPs). The testing materials consisted of 2 × 4 (38 mm × 89 mm) trembling aspen lumber pieces in lengths of 8, 10, and 12 feet (2.44, 3.05, and 3.66 m) with two visual grades, select structural (SS) and No. 2. Machine Stress-Rated (MSR), and longitudinal stress wave (LSW), edgewise third-point bending (EWB), and axial tension tests were conducted on the lumber. It was found that, (1) by increasing the maximum knot size by a half-inch from one-quarter inch, the minimum modulus of elasticity (MOE) measured using the MSR, the mean, and the fifth-percentile ultimate tensile strength (UTS) decreased by about 8.8%, 20.1%, and 29.8%, respectively. (2) Approximately 44% of the trembling aspen lumber met the 1450f-1.3E grade for MSR lumber, and 62% qualified for the 1200f-1.2E grade. (3) There was a great potential for manufacturing cross-laminated timber (CLT) of grade E3, with a rejection rate of about 29%. (4) The mean UTS and MOE values of the SS-grade trembling aspen lumber were 22.88 MPa and 9519 MPa, respectively, being 25.5% and 11.3% lower than that of Spruce-Pine-Fir (S-P-F) lumber. The fifth-percentile UTS and MOE values were 11.57 MPa and 7404 MPa, respectively, marking a decrease of 13.3% and 1.5% compared to the S-P-F lumber. (5) The oven-dried specific gravity (SG) of the trembling aspen wood was 0.40, which was about 3.5% larger than the value provided in the Wood Handbook.

Lateral behavior of wood frame shear wall using PVC wood-plastic composite (WPC) veneer panels

With the growing awareness of environmental protection and green ecology, there has been significant attention on the utilization of new energy-saving and environmentally friendly materials in building structures. This article proposes a novel structure for PVC wood-plastic composite wall panels. The structure comprises Polyvinyl Chloride (PVC) wood-plastic composite materials as the facing panel and SPF (Spruce-Pine-Fir) dimensional lumber as the wall framework, connected using self-tapping screws. In this study, two standard composite wall panel specimens were subjected to testing using both monotonic loading and low-cycle reciprocating loading methods. Finite element models of the composite wall panels were created using ANSYS Workbench software for analysis, investigating the lateral performance of PVC wood-plastic composite wall panels. The analysis results indicate that PVC wood-plastic composite wall panels exhibit favorable shear strength, elastic lateral stiffness, and lateral deformation as shear walls. The shear wall model can be accurately represented in finite element software, with minimal discrepancy between experimental and finite element analysis results. Consequently, the utilization of PVC wood-plastic composite wall panels as shear walls holds promise for future applications in the structural field.

Experimental investigation and evaluation of metal-plate-connected laminated bamboo lumber joints

This study focused on the mechanical performance of toothed metal-plate connected (MPC) laminated bamboo lumber (LBL) joints aiming to apply this metal-plate connection to the design and manufacturing of engineered bamboo trusses, due to the merits of the cost-effective and easy installation. A total of 212 MPC LBL and SPF (spruce-pine-fir) joints connected by the domestic toothed metal plates were tested in accordance with Chinese standards. Particular emphasis was placed on the load-slip behavior of metal plate teeth embedded in LBL with varied load direction related to the major axis of the toothed metal plate. Design values of the tensile and shear strength of the net section cross metal plate connector, and the anchorage and anti-slip strengths of the metal plate teeth embedded in LBL were presented in accordance with the existing timber design specification. Test results reveal that the metal plate orientation has a significant effect on the mechanical performance of MPC LBL joints. A new angular equation, expressed as the metal plate orientation, was proposed for evaluating the anchorage and anti-slip strengths of MPC LBL joints, which shows an obvious reduction in predicting error compared with the existing method. Design strength values of LBL joints are higher than those of the corresponding SPF joints, mainly due to the relatively smaller dispersion of LBL compared with SPF, indicating that the MPC LBL is expected to replace MPC timber in truss systems. The results of the comparison of MPC LBL and glubam (glued laminated bamboo) joints also suggest that arranging transverse bamboo strips is an available option for improving the anchoring mechanical performance of MPC LBL joints.

Evaluation of dowel bearing strength of fungal-decayed cross-laminated timber

ABSTRACT Dowel bearing strength of three cross-laminated timber (CLT) species (Douglas-fir, Norway spruce, spruce pine fir) were periodically assessed through 40 weeks of exposure to two brown rot fungi species (Gloeophyllum trabeum and Rhodonia placenta). Time-dependent regression models were developed to describe the relationship between level of fungal exposure and dowel bearing strength of CLT. Obtained dowel bearing strength values were used to predict the capacity of floor-to-wall CLT connection systems. Predicted strength values were compared with capacity of actual connection systems which were subjected to similar biodeterioration treatments. Significant reductions in the dowel bearing strength of CLT were observed 30 weeks after fungal inoculation. Similar patterns of degradation were observed for both fungi in all three CLT species, but R. placenta was slightly more aggressive than G. trabeum, causing a 16.2 MPa reduction in dowel bearing strength of Douglas-fir after 40 weeks of exposure. Connection capacities estimated using National Design Specification yield models for dowel type fasteners and the dowel bearing strength of fungal-damaged CLT were consistent with observed properties and were within 85% of actual capacity of connections tested, especially in early stages of decay.

A Study on Torsional Behavior of Glued Laminated Bamboo Glubam

Glubam is a type of engineered bamboo increasingly attracting research and application interest. This study focused on the torsional shear properties of glubam. Prismatic specimens with square sections were tested using a torsional loading device along with both conventional strain gauge–based instrumentation and a digital image correlation (DIC) system. Testing parameters included thick- and thin-strip glubams, the influence of carbonization of thick-strip glubam, as well as comparative spruce-pine-fir (SPF). Mechanical behavior and properties, including failure process, shear stress-strain relationships, modulus, and strength, were examined. The testing results indicated that carbonization of thick-strip glubam increased its strength slightly; however, specimens failed with more brittleness. The existence of bi-directional bamboo fibers in the thin-strip glubam apparently contributed to the larger deformability compared with the unidirectional thick-strip glubam.

The influence of internode geometry on the bearing capacity of parallel chord wood trusses

The influence of two factors, web angle and internode spacing, on the bearing capacity of three different configurations of trusses was investigated. The constitutive model of the bearing capacity of trusses was established which are jointly controlled by web angle and internode spacing. With bearing capacity and stability as calculation indexes, the critical web angle and internode spacing values for three different configurations of trusses were obtained quantitatively, the truss structure was designed by combining web angle and internode spacing, the mid-span displacement was further calculated as a theoretical basis for finite element simulation. A bearing capacity test on truss specimens with Spruce-Pine-Fir (SPF) as the base material was conducted using the obtained results. The relationship between the load displacement of the different geometric configurations of trusses and the main failure modes was determined accordingly. Finally, the constitutive model of bearing capacity was established which is jointly controlled by web angle and internode spacing. It was found that the stability of the bearing capacity of the A-type truss (Warren type with vertical bar) increases with an increase in the web angle, but is relatively unaffected by the web angle compared to other truss types. The bearing capacity of the B-type(Warren type) truss increases as the web angle increases and is markedly affected by the web angle. The bearing capacity of the C-type(Pa type) truss decreases as the web angle increases, but this configuration is less affected by the web angle than the B-type. The influence of internode spacing on the load-carrying capacity of the truss weakens with an increase in the web angle, as well. The constitutive model, which was obtained by theoretical calculation and ABAQUS finite element simulation, is valid within the elastic deformation range but is not applicable beyond the elastic deformation range.

Bending performance of nail laminated timber: Experimental, analytical and numerical analyses

Nail laminated Timber (NLT) is a kind of mass timber product becoming popular in recent years. To further understand the bending performance of NLT and motivate its utilization in engineering, experimental, analytical and numerical analyses were conducted in this study. Spruce-pine-fir (SPF) dimension lumber was used as the lamination to fabricate the NLT and four-point bending test was conducted on ten NLT specimens. The failure modes, modulus of elasticity and load-carrying capacity of the NLT were investigated. Results showed that the dominant failure mode of specimens was tension failure at the bottom of the laminations. The bending strength of the NLT corresponding to the occurrence of the first lamination failure was about 11.4% lower than the ultimate bending strength. The average modulus of elasticity and the average ultimate bending strength of the NLT were close to those of the laminations. Considering the property difference of the laminations, an analytical method was proposed to analyze the internal force of NLT. Then, the finite element model of NLT was established and further calibrated by the experimental and analytical results. The comparison proved that both the analytical and numerical methods could effectively predict the bending performance of NLT.

Behaviour of hybrid cross laminated timber in compression perpendicular to grain in different layup structure, support conditions, and loading configurations

Cross laminated timber (CLT) is recognized as alternative to traditional construction materials. As a floor member, it causes the compressive deformation or even damage perpendicular to the grain of CLT due to vertical load imposed by the column or wall. The challenge is how to improve the compressive strength (fc,90) and elastic modulus (Ec,90) perpendicular to the grain under the high diversity of possible load configurations. Compared with normal CLT, hybrid CLT (HCLT) used structural composite materials (e.g. laminated strand lumber) instead of timber, which had more homogeneous mechanical properties. In this study, the spruce-pine-fir (SPF) and laminated strand lumber (LSL) were used to prepare HCLT. The full surface loading, point loading representing columns and line loading representing walls of HCLT in the perpendicular to grain direction were carried out. The results show that fc,90 increased with increasing thickness ratio of LSL in the total thickness of HCLT under full surface loading, the highest increase in strength of HCLT reached 35.71 %, data of Ec,90 had the opposite conclusion. In the case of point loading, the fc,90 and Ec,90 under discretely support was lower than those under successively support. Load configuration had significant influence on the fc,90 and Ec,90 including middle position (M), corner position (C), edge parallel (E) and edge vertical (V) to the grain of the outer layer. In the case of line loading, it was in good agreement with point loading results, and fc,90 and Ec,90 under line loading were lower than that under point loading. The failure modes were mainly the cracks along the wood ray direction of SPF material, while no obvious damage for LSL under full surface loading. In addition, the failure modes mainly of local loading included the shear failure for SPF material, fiber fracture failure of LSL material and the adhesive layer cracking in the non-directly compression zone.

Acoustic properties of glued laminated bamboo and spruce-pine-fir

Noise pollution has become a worldwide issue, which has a negative effect on human health. The sound reduction index and absorption coefficient of glued laminated bamboo (glubam) and spruce-pine-fir (SPF) were firstly measured in this study by using the impedance tube method. The effect of moisture content on the acoustic performance of these materials was also investigated. Experimental results revealed that for thick-strip glubam and SPF, the higher moisture content, the higher sound reduction index but lower sound absorption coefficient. However, moisture content does not have an obvious effect on acoustic properties of thin-strip glubam. By comparing with other materials, it can be found that glubam and SPF have relatively high normal-incidence transmission loss but low absorption coefficient and noise reduction coefficient. Glubam shows the similar but even better acoustic insulation performance than SPF, which confirms the possibility of using glubam as an alternative of wood materials. Moreover, a finite element model was built up to simulate the measurement of sound transmission loss in an impedance tube. Some parametric studies were then conducted using the finite element model to prove the effectiveness of increasing thickness, using composites and double-layer panels on improving the soundproof performance of materials.

Bonding performance of cross-laminated timber-bamboo composites

Bamboo is one of the most important renewable resources in China, leading to the development of bamboo products as well. Alternative applications of bamboo need to be developed in the field of construction, especially in cross-laminated timber (CLT) construction, due to better mechanical performance of bamboo and the increasing popularity of CLT construction in recent years. The bonding performance of cross-laminated timber-bamboo (CLTB) composites fabricated with Spruce-pine-fir (SPF) dimension lumber and bamboo scrimber boards was investigated here. L9 (34) orthogonal experiments with four factors (adhesive type, adhesive spreading rate, clamping pressure, and clamping time) and three levels were applied to evaluate their impacts on the bonding indicators of CLTB through block shear and delamination tests. Results showed that adhesive type had the most critical influence on the bonding performance. The optimal manufacturing parameters were adhesive of phenol resorcinol formaldehyde (PRF), adhesive spreading rate of 250 g/m2, clamping pressure of 1.0 MPa, and clamping time of 420 min, respectively. PRF adhesive yielded higher block shear strength, wood failure percentage, and lower rate of delamination than one-component polyurethane (PUR) and emulsion polymer isocyanate (EPI), especially under wet or boiling condition.

The Dimensional Stability and Bonding Performance of Hybrid CLT Fabricated with Lumber and COSB

The differences of physical and mechanical properties of different laminations, such as softwood, hardwood or other structural composite lumber, in hybrid cross-laminated timber (HCLT), lead to their dimensional stability and bonding performance more complex than generic cross-laminated timber (CLT). In this paper, the spruce-pine-fir (SPF) dimension lumber and construction oriented strand board (COSB) were employed to fabricate HCLT. The effects of four configurations and three adhesives on the dimensional stability and bonding performance of CLT and HCLT were evaluated in term of the water absorption (WA), thickness swelling (TS), block shear strength (BSS), wood failure percentage (WFP) and rate of delamination (RD). The results showed that with the increase of the COSB laminations, the WA of HCLT specimens decreased, and the values of TS, BBS and WFP increased. The configuration had a significant influence on the dimensional stability, BBS and WFP of the specimen. The adhesive had a significant influence on the dimensional stability and some bonding performances of the specimen. The phenol resorcinol formaldehyde (PRF) specimens had the lowest average RD value compared with the one-component polyurethane (PUR) and emulsion polymer isocyanate (EPI) specimens. Failures were prone to occur in the middle of the thickness of COSB lamination during block shear and delamination tests. The outcome of this paper could help the engineering application of HLCT.

Uplift capacity evaluation of light-framed wood structure’s roof-to-wall connections

The load-displacement curves of six types of roof-to-wall connection joints were obtained through uplift experiments, while the mechanical properties of each type of joint were compared and analyzed, and the applicability of each joint was verified by the Foschi load-displacement curve model simulation. The specimens were made of three kinds of wood (Pinus sylvestris (PS), Spruce-Pine-Fir (SPF), and Douglas fir (DF)) and two different metal connectors (A-type and B-type), and then the monotonic pullout tests were conducted on each specimen. The failure modes of each group of specimens were analyzed, and the characteristic values analysis method was used to analyze and compare the characteristic values of the load-displacement curves of each specimen, including six characteristic values: maximum load, yield load, deformation capacity, energy dissipation capacity, ductility ratio, and initial stiffness. The results showed that the load capacity of TA group (specimens with A-type metal connectors) was much greater than that of TB group (specimens with B-type metal connectors). The specimens made of DF had the best mechanical performance, but the specimens of DF group were prone to brittle failure. Finally, the fitting parameters of the Foschi model applicable to such joints were obtained.

DESIGN AND PERFORMANCE OF NAIL CONNECTION IN WOOD FRAMING SHEAR WALLS

As the preferable lateral resistance system of a wood shear wall is attributedto the good lateral performance of nail connection, this paper aims at investigating the pull-out and shear performances of framing members’ nail connection in wood shear walls under monotonic loading. It was found that the main failure mode of the pull-out behavior of nail connection was the withdrawal of threaded nails from framing members. In addition, the shear behavior of nail connection was characterized by plastic hinge of threaded nails, local tear of spruce-pine-fir(SPF)on the top of nails, and nail caps that were obliquely embedded into the surface of SPF. The average ultimate load and displacement of shear mode were 1.48 times and 5.12 times higher than those of pull-out mode, respectively.According to the research results, thecorresponding exponential numerical model was established, which provided basic data for the lateral performance research and finite element simulation analysis of wood shear walls nail connection.

Strength Performance of the Connection between Brick and SPF Lumber

There are many ways to strengthen an unreinforced brick masonry wall. One of the strengthening methods applies timber, which is a lightweight and easy installation. The connection between the timber and the brick masonry wall plays an important role. In this study, the experimental and theoretical methods were investigated, and the pullout and shear strengths of the chemical anchor were employed as the connection between clay brick and SPF (spruce, pine, fir) lumber. Three bolt diameters (ø8, ø10, ø12 mm) were utilized in nine pullout tests and two types of eighteen shear tests. Four types of prediction models estimated the pullout strength of the chemical anchor. The European Yield Theory (EYT) expected the shear strength of the chemical anchor, involving six failure modes. The results of all experiments were discussed as failure mode, strength, and stiffness under monotonic load. Finally, the effective result of this study highlights A12 specimens using ø12 mm bolt and employing the epoxy resin in brick and lumber. The maximum pullout load of A12 specimens is 12.1 kN, and the yield shear load is 11.2 kN.

Acoustic Emission Characteristics of Different Bamboo and Wood Materials in Bending Failure Process

The acoustic emission (AE) technique can perform non-destructive monitoring of the internal damage development of bamboo and wood materials. In this experiment, the mechanical properties of different bamboo and wood (bamboo scrimber, bamboo plywood and SPF (Spruce-pine-fir) dimension lumber) during four-point loading tests were compared. The AE activities caused by loadings were investigated through the single parameter analysis and K-means cluster analysis. Results showed that the bending strength of bamboo scrimber was 3.6 times that of bamboo plywood and 2.7 times that of SPF dimension lumber, respectively. Due to the high strength and toughness of bamboo, the AE signals of the two bamboo products were more abundant than those of SPF dimension lumber. However, the AE evolution trend of the three materials was similar, which all experienced three stages, including gentle period, steady period and steep period, and the area of rupture precursor characteristics could be recognized before the specimen destroyed. Due to the bottom layer was first tensile failure, the main structure of bamboo plywood was destroyed after the stress redistribution. The rupture precursor characteristics could be observed before each peak. Findings put in evidence a good correlation between AE clusters of two bamboo products, while the amplitude and energy of wood signals were lower than those of bamboo. The amplitude and energy from the propagation and aggregation of cracks were greater than those related to micro-cracks initiation.

Low-cycle fatigue life and duration-of-load effect for hybrid CLT fabricated from lumber and OSB

Given the nature of cross-laminated timber (CLT), with an orthogonal arrangement and rolling shear characteristics of transverse layers, it has a more complex duration-of-load (DOL) effect than other engineered wood products, such as glued-laminated timber. Developing hybrid CLT (HCLT) with structural composite lumber, which can improve the mechanical properties and material sources of CLT, is gaining increasing interest. Construction oriented strand board (COSB) and spruce-pine-fir (SPF) dimension lumber were used to fabricate HCLT specimens for this study. The regular SPF CLT and HCLT specimens having different lay-ups and numbers of layers were subjected to low-cycle fatigue bending and shear loading tests. The Foschi and Yao damage accumulation model was calibrated using the test results. The DOL factors for the CLT and HCLT specimens were calculated using the stress ratio evaluation method. Results showed that the primary failure modes for the fatigue test specimens were the same as those observed in previous short-term ramp loading tests, and a good fit was observed between the model's predictions and the test data. The DOL factor corresponding to a load duration of 50 years, for a three-layer shear CLT specimen, was determined to be 0.53, which was lower than that recommended in CSA O86-19. The fatigue life and long-term performance of CLT were improved by using COSB panels as CLT layers. The HCLT specimens that used COSB only as the transverse layer showed advantages in fatigue life, long-term performance, and practical applications.

EXPERIMENTS AND RELIABILITY ANALYSIS ON FRAME-TO-SHEATHING JOINTS IN LIGHT WOOD FRAMED SHEAR WALLS

To exploit the spruce-pine-fir (SPF) panel and the parallel strand bamboo (PSB) panel used in light wood framed shear wall and investigate the lateral behaviors of frame-to-sheathing joints in light wood framed shear wall with different characteristics, the experimental investigation and reliability analysis were carried out under monotonic load. The test configurations included joints with perpendicular-to-framing-grain load or parallel-to-framing-grain load, with SPF sheathing panel or PSB sheathing panel and with nail or screw. The results suggested that nailed joints with PSBpanel occurred ductile failure but other joints occurred brittle failure. Moreover, theultimate bearing capacity and the elastic stiffness of the joints under perpendicular load were higher than that ofthe joints under parallel load. The use of PSB panel and screw increased theultimate bearing capacity of the joints. Furthermore, based on Johansen yield theory and experimental results, the reliability analysis was carried out through first-order reliability methods. The results showed that the SPF-nail joints, the PSB-nail joints, and PSB-screw joints achieved the reliability requirements.