Clear Specimens Research Articles

Mechanical Properties of Wooden Structural Members from a Historical Japanese Temple Under Renovation – and the Effects of Cross-Sectional Voids and Aging

ABSTRACT Using wooden structural members removed from a 500-year-old Japanese temple under renovation as specimens, the effects on the mechanical properties (dynamic Young’s modulus) brought about by cross-sectional voids such as mortises and insect holes, were examined. Then, in order to examine the effects of aging, small clear specimens were cut from the removed structural members (aged wood) and store-bought timbers (new wood), and their mechanical properties (dynamic Young’s modulus, tensile Young’s modulus and tensile strength) were compared. When all voids were eliminated from the removed aged wood, the dynamic Young’s modulus increased by a factor of 1.55. The results for the small clear specimens showed that the dynamic Young’s modulus and tensile Young’s modulus were similar for the aged and new wood, while the tensile strength of the aged wood was 42% lower on average than that of the new wood. Although eliminating cross-sectional voids in the removed aged wood improved mechanical performance, it was found that even in a void-free condition, the tensile strength of wood decreased significantly due to aging, suggesting that the use-environment should be considered when reusing removed timber.

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.

Timber Strength Grading as Necessary Basis for Structural Design in ex-YU Region

The aim of this paper is to contribute to the classification of structural timber in the ex-YU region into strength-class system through the application of experimentally obtained archive data in order to provide a realistic framework for most commonly used II grade (according to JUS) structural coniferous timber. The analysis of archive data was carried out on a sample of 150 specimens of structural size and based on the set of statistical requirements prescribed by EN standards, taking into account the change in disposition of loading in laboratory testing in the past and now. Statistical procedures prescribed by EN standards are given through calculation steps together with necessary adjustment factors that cover the size and number of specimens. The presented procedures given for structural-size specimens are also applicable to small clear specimens, so that a more comprehensive research and additional new examinations could be conducted with the available archive data simultaneously with the harmonization of the visual classification rules applied in the ex-YU region. The paper emphasises the direct dependence of the consistent application of the visual grading rules required by the relevant EN standard on strength-class system.

Effect of slope of grain on mechanical properties of some tropical wood species

ABSTRACT The aim of this work was to study the relationship between the mechanical properties of Cameroonian tropical woods and the slope of grain. The forests of the Cameroonian part of the Congo Basin abound in species that are highly solicited for structural applications. However, little information is available on the influence of the slope of a grain of these wood species. Clear wood specimens of ayous (Triplochiton scleroxylon), azobe (Lophira alata), fraké (Terminalia superbe), okan (Cylicodiscus gabunensis), padouk (Pterocarpus soyauxii), and sapelli (Entandrophragma cylindricum) were prepared. The specimens have a cross section of 20 × 30 mm and a length of 300 mm. These specimens were subjected to a four-point bending test and a double cantilever beam test. Modulus of elasticity (MOE), modulus of rupture (MOR), work at maximum load (WML) and fracture toughness (GIC) were determined. These mechanical properties were calculated for specimens with slopes of grain 0°,15°, 30°,45°,60°, 75° and 90°. The results showed that the slope of grain had significant effects on all the mechanical properties measured on clear wood specimens. MOE, MOR, WML, and GIC decreased with increasing grain slope. On the other hand, azobe and okan absorb much more of the energy that causes microcracking than the other species.

Within-tree variation regarding ultrasonic velocity, wood density and compressive strength of the eucalypt hybrid (Eucalyptus urophylla × E. pellita)

ABSTRACT A variation study of the ultrasonic velocity (Vu ), wood density (AD), and compressive strength (CS) within trees (longitudinal and radial) of the eucalypt hybrid uropellita (Eucalyptus urophylla × E. pellita) was carried out for the first time. Vu was measured in pith-to-bark strips collected from six stem height levels (0.5, 1.5, 2.5, 3.5, 4.5, and 5.5 m above the ground) in the longitudinal axis using air-coupled ultrasonic techniques, and AD and CS were measured for small clear specimens obtained from these strips. In general, Vu increased outwards from the pith with increasing stem height. The overall mean values of Vu , AD, and CS were 2872 m/s, 0.50 g/cm3, and 41.40 MPa, respectively. Within the stem, the radial position was highly significant (P < 0.001) for all traits, whereas the longitudinal variation was significant only for Vu but its contribution was small (approximately 9% of the total variation). Vu and AD had significant (P < 0.05) positive linear correlations with CS in both the radial position and combined radial positions. The best prediction of CS was obtained when Vu and AD were used together by calculating the dynamic modulus of elasticity (Ed ).

Acetylation- and ubiquitination-regulated SFMBT2 acts as a tumor suppressor in clear cell renal cell carcinoma

BackgroundClear cell renal cell carcinoma (RCC) is the most common kidney tumor. The analysis from medical database showed that Scm-like with four MBT domains protein 2 (SFMBT2) was decreased in advanced clear cell RCC cases, and its downregulation was associated with the poor prognosis. This study aims to investigate the role of SFMBT2 in clear cell RCC.MethodsThe expression of SFMBT2 in clear cell RCC specimens were determined by immunohistochemistry staining and western blot. The overexpression and knockdown of SFMBT2 was realized by infection of lentivirus loaded with SFMBT2 coding sequence or silencing fragment in 786-O and 769-P cells, and its effects on proliferation and metastasis were assessed by MTT, colony formation, flow cytometry, wound healing, transwell assay, xenograft and metastasis experiments in nude mice. The interaction of SFMBT2 with histone deacetylase 3 (HDAC3) and seven in absentia homolog 1 (SIAH1) was confirmed by co-immunoprecipitation.ResultsIn our study, SFMBT2 exhibited lower expression in clear cell RCC specimens with advanced stages than those with early stages. Overexpression of SFMBT2 inhibited the growth and metastasis of clear cell RCC cells, 786-O and 769-P, in vitro and in vivo, and its silencing displayed opposites effects. HDAC3 led to deacetylation of SFMBT2, and the HDAC3 inhibitor-induced acetylation prevented SFMBT2 from SIAH1-mediated ubiquitination modification and proteasome degradation. K687 in SFMBT2 protein molecule may be the key site for acetylation and ubiquitination.ConclusionsSFMBT2 exerted an anti-tumor role in clear cell RCC cells, and HDAC3-mediated deacetylation promoted SIAH1-controlled ubiquitination of SFMBT2. SFMBT2 may be considered as a novel clinical diagnostic marker and/or therapeutic target of clear cell RCC, and crosstalk between its post-translational modifications may provide novel insights for agent development.

Analyzing the effects of size and density on the ultimate compressive strength of structural laminated bamboo parallel to the grain

Considering the influence of natural flaws of raw materials and procedures, the size effect is an inherent characteristic that is critical when applying most construction materials. This study focuses primarily on the compressive properties of laminated bamboo, which has become increasingly popular in construction due to its durability and strength. Two specimen sizes (25 × 25 × 100 mm and 50 × 50 × 200 mm) and three densities (0.60, 0.67, and 0.69 g/cm3) were evaluated under uniaxial compression. As a result of this study, the size effect is examined in terms of failure mode, mechanical property, data distribution, and description model, as well as introducing the size effect model with density in an innovative manner. To investigate the effect of specimen size on compressive strength along the grain direction, data analyses were performed. These analyses included failure mechanism analysis, distribution testing, and descriptive model development. According to the results, the compressive strength decreases with increasing dimensions, averaging 62.29 MPa–56.93 MPa, with a decrease rate of 8.60 %, although the failure modes are seldom different. In accordance with the increase in density, the rate of strength reduction also increases, and shows an approximate linear relationship with density. With the change in size, the distribution of the data changes, resulting in a reduction of up to 13.34 % in the standard value. The weakness-link model is better suited for describing data than fracture energy models and fractal theory models, based on which reduction ratios are predicted. By adding density to the size effect model, a more accurate prediction model can be derived between size, density, and compressive strength. As a result of these investigations, we will gain a better understanding of the gap between small clear specimens and large members, as well as those key influences necessary to optimize the use of laminated bamboo in structural applications.

Mechanical properties of jabon (Neolamarckia cadamba (Roxb.) Bosser) wood 13 years old and its potential utilization as a structural material

Jabon (Neolamarckia cadamba (Roxb.) Bosser) is a type of fast-growing tree that is expected to meet the national demand for wood because it has fast-growing properties. This study’s objective was to examine the mechanical properties of 13 years old jabon wood based on its position in the stem. The preparation of mechanical properties test samples and their tests refer to the British Standard (BS) 373 Methods of testing small clear specimens of timber and the American Society for Testing and Materials (ASTM) D143 Standard test method for small clear specimens of timber. Based on the results of the study, the stem parts (bottom, middle, and top) had no significant effect on the mechanical properties of wood except for the compressive strength parallel to the grain and hardness. In general, the mechanical properties showed an increase from the bottom to the top of the stem and from the pith toward the bark, although there were some differences. The mechanical properties of jabon wood obtained from this study generally showed higher values than jabon wood used in other studies with younger ages, although in general, it did not change the category of jabon wood from strength class III-IV. However, its use as a structural material would be more profitable than using a younger age of jabon wood, as it is usually harvested so far.

Cross-Laminated Timber (CLT) in Compression Perpendicular to the Plane: Experimental Analysis on the Column below the Wall Load Configuration

This study investigates the load-bearing properties of cross-laminated timber (CLT) under compression perpendicular to the grain. Different series of CLT panels with varying layups, layer thicknesses, and overall depths were tested. Also, the compression perpendicular to the grain properties of CLT plate specimens is compared against clear wood and cubic CLT specimens. The results show a 30% reduction in modulus perpendicular to the grain for cubic samples compared to clear specimens. Increasing the number of layers from three to five leads to a 21% higher modulus, while increasing the overall depth from 105 to 175 mm results (with the same number of layers) in a 17% reduction. The overall depth significantly affects the CLT’s modulus and strength under compression perpendicular to the grain. The study also compares two analytical models for determining the transversal compression factor, kc,90. Although the models showed satisfactory results for thinner CLTs, their accuracy decreased with greater panel depth. These findings enhance the understanding of CLT panels for structural applications.

Wood Material Properties of Forest Fire-Damaged Norway Spruce and Scots Pine for Mechanical Wood Processing in Finland

Due to climate change, the risk of forest fires has increased in Europe, resulting in challenges in the allocation of salvaged wood. We studied the raw material potential for wood products of Norway spruce and Scots pine sawn log trees that remained standing after a large forest fire in Kalajoki, Finland, in July 2021. Eight burned trees, with four reference trees per species, were sampled as standard specimens, and measurements were analyzed with linear mixed models. The effects of fire on the modulus of elasticity and rupture, Brinell hardness, moisture gradient, and color were measured on clear wood specimens of sapwood and heartwood. The wood density, level of fire damage, and height location of a tree were used as additional predictors. The results show some changes in the sapwood material. Spruce wood underwent stronger changes after the fire than pine wood, probably due to spruce wood having a thinner bark and a longer crown. The moisture content decreased in spruce, and the color darkened in both spruce and pine. Changes in the mechanical properties were mostly negligible, but a small increase in the Brinell hardness in spruce and a small decrease in the modulus of rupture in pine were observed. Fresh salvaged wood can be a suitable material for middle-quality and lower-quality wood products. The spread of char and soot into wood and wood processing machinery still limits its usage, especially for spruce.

Manufacturing Process, Tensile-Compressive, and Impact Properties of Tungsten (W)-Particle-Reinforced SLA Methacrylate.

The interest in research and development for additive manufacturing (AM) processes has grown significantly over the last years and attracts both industry and academia alike. Among the available AM technologies, stereolithography (SLA) is one of the most discussed, researched, and employed. On the other hand, being based on thermoset resins, all the limitations of this typology of materials still apply, limiting the range of applications of this highly versatile process. To overcome these limitations, especially brittleness, this research analyzes the effects of Tungsten (W) micro-size (average size 1 μm) particles reinforcement on a methacrylate base material. First, the manufacturing process for creating the W-reinforced methacrylate material is presented and investigated to define the effect of pre- and post-processing operations on the quality of the pre-cured solution considering 4% and 10% wt. W particles concentrations. Afterward, tensile, compressive, and impact specimens were manufactured with both concentrations and compared with the experimental results from clear (unfilled) resin-based specimens used as the benchmark. The addition of tungsten particles showed a strong improvement in the impact strength of the methacrylate base material, quantified in 28% for the 4% and 55% for the 10% wt., respectively, although at the expense of a slight reduction in elastic and yield properties on average -12%. Furthermore, using Scanning Electron Microscope (SEM) analyses, the particle-matrix interaction was investigated, showing the interaction between the polymer matrix and the reinforcement and the mechanism by which the impact resistance is enhanced.

Experimental investigation on the influence of microwave technology on the treatability and mechanical properties of Portuguese southern blue gum wood

Despite presenting global relevance and satisfactory mechanical properties for structural applications, the Portuguese eucalyptus, southern blue gum (Eucalyptus globulus Labill.), faces difficulties with impregnation with preservative products due to its limited permeability (treatability), which limits its utilization. Microwave (MW) treatment of wood offers a promising avenue for overcoming this issue, but it may impact the mechanical properties. It was identified that there remain research gaps regarding the impacts of MW treatment on eucalyptus. Hence, it was aimed to identify the optimum MW parameters for southern blue gum wood to enhance its impregnability without compromising the mechanical properties. This will contribute to meeting the growing demand for wood for construction. Small clear wood specimens containing heartwood were separated into three groups: two underwent MW treatment, and one did not (control). The samples were impregnated with a preservative product and after submitted to mechanical testing. The MW treatment significantly enhanced the retention of the preservative product, which is remarkable given the impossibility of impregnating eucalyptus heartwood using conventional pressure methods. Although there were slight decreases in the mechanical properties of the MW-treated specimens, they were statistically equivalent to the control group. New insights into the mechanical bending behavior of MW-treated samples also arose. The mechanical properties of MW-treated eucalyptus samples surpassed those of other globally used wood species. Thus, MW treatment presented itself as an effective process for increasing eucalyptus impregnability, and it has the potential to augment southern blue gum's use as a raw sawn and engineered structural wood material worldwide.

Macroscopic material degradation model of Norway spruce clear wood for XFEM

The study aims at investigating the failure behavior of Norway spruce clear wood specimens using XFEM by modeling earlywood and latewood growth rings. The growth ring pattern in the specimens are determined using a photo-analytical processing program. For the simulations, 6 damage initiation mechanisms were considered and the subroutines were implemented in the finite element solver ABAQUS. A normal vector to the crack surface is calculated for each damage mode, taking into account the orientation of the maximum and minimum principal stresses. The XFEM model and the material properties are calibrated based on experiments, where the edge-notched specimens were subjected to 3-point bending, tensile and compression tests. The goal is to determine the ultimate load, locate structural weakpoints and obtaining a realistic crack propagation path by means of XFEM.

Experimental and numerical investigation of the laser shock-based paint stripping process on CFRP substrates

Various laser shock wave applications have been proposed for metals; the most popular is the laser shock peening. In composites, the use of the laser shock wave technology is still at an early stage. Laser shock paint stripping (LSPS) is a method where a laser-induced shock wave is used to remove a paint from a substrate. In this study, a combined experimental–numerical study was performed on the LSPS on Carbon Fiber Reinforced Polymers (CFRP) substrates. Two types of specimens were investigated: specimens with an epoxy structural primer covered by a polyurethane base and a clear coat and specimens with the above layers plus an epoxy exterior primer between the epoxy structural primer and the polyurethane layer. The specimens were shot using various laser intensities aiming to obtain the stripping threshold and the stripping percentage as functions of the laser intensity. The diameter of the stripped area was measured by a profilometer. An electron microscope was used to evaluate the stripping efficiency. In parallel, a numerical model was developed using the LS-DYNA explicit Finite Element (FE) software. For the modeling of the CFRP, a progressive damage model with strain rate parameters was used while for the epoxy an elastic–plastic-hydrodynamic material model combined with the Gruneisen equation of state. The interface between these two materials was modeled using cohesive zone elements of zero thickness, which follow a bi-linear traction-separation law. Calibration of the modeling of the shock wave propagation inside the composite material was achieved through the comparison of the back-face velocity profiles, measured by a velocity interferometer system for any reflector system. The results from the multiple tests conducted revealed the repeatability of the process and the significant effect of the laser intensity. On the other hand, the model managed to predict well the back face velocity–time profile but in most cases, it failed to predict the stripping pattern. This is mainly due to lack of crucial material properties and the assumptions made in the modeling of the applied pressure profile.

Microwave Treatments and Their Effects on Selected Properties of Portuguese Pinus pinaster Aiton. and Eucalyptus globulus Labill. Wood

The most widespread wood species in the Portuguese forest and the most widely utilized are maritime pine (Pinus pinaster) and eucalyptus (Eucalyptus globulus Labill). In the case of eucalyptus, except for the pulping sector, it might have limited usage due to drying issues and low permeability. Microwave (MW) treatment is a technology that has been used to improve wood species’ permeability. Therefore, the present paper aimed to evaluate the MW treatment of both Portuguese wood species and to investigate the effects of different MW treatments on wood’s density, water uptake capability, modulus of rupture (MOR), and modulus of elasticity (MOE). Using small clear wood specimens, two MW powers were used, 700 and 1200 W, and the samples were submitted to successive MW cycles of 2 min till they reached the required dryness. The results showed that each wood species had a different behavior during the MW drying in terms of drying rate, supply, and consumption of energy. In general, with the increase in MW power, the densities of both species decreased and the water uptake increased, as a possible indicator that a certain level of microstructural damage might have occurred. Regarding the mechanical properties of MW-treated maritime pine and eucalyptus wood specimens, under the harshest conditions (MW power of 1200 W), MOR and MOE were reduced compared with the wood sample without MW treatment.

Characteristics of Simalambuo (Lophopetalum sp.) wood from Nias Island, North Sumatra Province, Indonesia

Abstract. Iswanto AH, Amanda DW, Gea S, Susilowati A, Fatriasari W, Darwis A, Lubis MAR, Sucipto T, Syahidah, Subekti N, Hartono R, Sutiawan J, Hidayat W, Kim NH. 2023. Characteristics of Simalambuo (Lophopetalum sp.) wood from Nias Island, North Sumatra Province, Indonesia. Biodiversitas 24: 4193-4201. Simalambuo (Lophopetalum sp.) wood is commonly used for construction materials in Nias Island, North Sumatra Province especially in the aftermath of the devastating earthquake that affected the region. However, information regarding the fundamental characteristics of this wood has not been available. Therefore, this research aimed to evaluate the basic properties of Simalambuo wood, such as its physical, mechanical, chemical, and natural durability. The destructive method was used to determine the physical and mechanical parameters (i.e., specific gravity, moisture content, shrinkage, MOE, MOR, and hardness) using a small clear specimen sample under the BS 373 standard (1957). The chemical components of wood (i.e., holocellulose, cellulose, lignin, extractives) were analyzed using a variety of methods, including CRC Press methods, LAP NREL 003 standard, and TAPPI. Meanwhile, the SNI 7207-2014 standard was utilized to evaluate its resistance against subterranean termites. The results showed that Simalambuo wood has an average specific gravity of 0.42 and a T/R ratio of 1.78. Based on its specific gravity, the wood is classified within the strength class III-IV. It also exhibits a reduced cellulose and extractive content, along with a higher proportion of lignin. In terms of durability, it is classified as class IV, implying non-resistance to termites’ attack and necessitating wood preservation treatment for its practical application. The findings of this study suggest the application of this wood is recommended for light construction, furniture, and other functions, but not for heavy construction.

THE POTENTIAL OF PRODUCING HIGH ADDED VALUE STRUCTURAL TIMBER FROM LAMELLAE WASTE. CLASSIFICATION AND VISUAL GRADING

This study is the continuation of the first part (Horváth et al. 2023), in which density, bending strength and modulus of elasticity of 100 oak lamellae generated as small-sized production waste were investigated. In this part of the study series, the classification of our sample set is carried out according to the EN 338. A visual pre-grading is presented, to remove the worst specimens and achieve a better final result and a standardized visual grading is also shown. Our results are compared with literature values of clear specimens as well. Amount of 80% of the specimens were found to be suitable for further structural use. The total sample set is classified in strength class D35 (average density 712.6±72.5 kg/m3; average MoRadj 65.4±16.2 MPa; average MoEadj 13.4±3.1 GPa), while the visually pre-graded part with better average test results is classified in strength class D45. Industrial wood residues contain a sufficiently high proportion of elements for further processing, so that after sorting it can be used as raw material for glued-laminated load-bearing timber.

Effects of seismic strain rates on the perpendicular-to-grain compression behaviour of Dahurian larch, Mongolian pine and Chinese poplar: tests and stress-strain model

Abstract Wood is mainly subjected to transverse compression in many critical parts of Chinese traditional timber structures, e.g. the mortise-tenon and Dou-Gong joints. Seismic is one of the dynamic actions faced by these structures and will cause wood to suffer higher loading speeds than quasi-static loads. The investigation of the seismic strain rates (SSRs) effects of wood under perpendicular-to-grain compression (PTGc) is important. One hundred and forty-four radial small clear wood specimens were prepared using Dahurian larch, Mongolian pine and Chinese poplar. Monotonic and cyclic compression tests were conducted under three SSRs (10−3 s−1, 10−2 s−1, and 10−1 s−1) and the quasi-static strain rate (10−4 s−1). Failure modes, stress-strain curves, yield strengths, elastic moduli and the unloading/reloading moduli were analyzed. Results indicated that the PTGc properties were highly sensitive to SSRs under both the monotonic and cyclic compression. Strengths showed higher sensitivity to SSRs than elastic moduli. The SSRs effects of wood under cyclic compression have greater variability than the monotonic counterparts. The unloading/reloading moduli shows little SSR effects statistically. Comparisons were made between the existing PTG and the parallel-to-grain test results and a fitted general expression was obtained. Furthermore, an SSR-dependent stress-strain model was proposed and verified by tests.

A versatile study on neuron deformation of brain through photonic structure

The neuron connections in the central nervous system play an important role in the structure of the life organ. The neurons control the operational mechanism of an entire brain which sways the intact system of the body. An itty bitty variation of neurons in the brain creates a serious complication which may lead to the brain haemorrhage. The amount of the variation/deformation of neuron in brain determines the stage of the brain stroke. So an early computation of the deformation of neuron saves from brain haemorrhage. Keeping the importance of the neuron deformation in the brain, the present article employs one dimensional photonic structure to fetch the amount of deformation in the brain using infrared (IR) signal of 1310 nm (wavelength). The principle of measurement of the deformation relies on the light transmittance characteristics of three layers of photonic structure which contains the tissues of the brain. The output power emerging from one dimensional photonic structure indicates the status of the neuron deformation. The output result infers that the amount of deformation of the of neuron decreases linearly with the increasing of an output power. Same techniques are applied for both focusing clear and CLARITY specimen for the sake of validation. For example; the outcomes of the same specify that the output power decreases from 23.9923 µW to 0.0076 µW for deformation raging from 1.0 µm to 1.4 µm of the brain from CLARITY. Similarly, the output power decreases from 29.1294 µW to 0.27956 µW for deformation raging from 1.0 µm to 1.4 µm of the brain from focus clear method. To sum up, the outcomes of the current research confirms that the amount of the deformation in the brain can be identified by knowing the output power. In short, the present work proposes a photonic crystal based sensor through which one can fetch the amount deformation of the brain by knowing the amount of transmitted signal at the output end. For example; the neuron deformation which is ranging from 1.0 µm to 1.4 µm could be known instantly by applying 1310 nm to the proposed photonic structure.

Bending strength prediction and finite element analysis of larch structural beams

The material constants of wood required for finite element analysis (FEA) are usually calculated using small clear specimens. However, defects, such as knots and slope of grain affect the strength reduction in the full-size specimens. Consequently, an error occurs if only the material constant calculated from the small clear specimens is used to predict modulus of rupture (MOR). Therefore, in this study, the MOR reduction coefficient according to defect was obtained through the bending test of the full-size specimens and applied to the FEA, in addition to the material constant from the small clear specimens. The maximum bending moment section was measured for a 3-section four-point load, and defects in the outermost tension layer were measured for laminated timber and glulam. The result of the bending test confirmed that MOR also decreased as the size of the defect increased. Therefore, when predicting MOR, a strength reduction ratio according to visual grade was applied. The MOR predicted FEA was twice as large as the actual MOR before defect correction, but the prediction error after defect correction was greatly reduced to 8%, thus increasing the prediction accuracy.