• Journal of the Korean Wood Science and Technology
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• v.21 no.2
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• pp.15-22
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• 1993

This study was carried out to investigate the fracture criterion of glulam. The mixed mode fracture of glulam was investigated by means of single edge notched specimens with various crack inclination in the longitudinal-radial plane. While fracture of wood is not completely understood, the study on linear-elastic fracture mechanics is a rational and valuable tool for studying the strength behavior of glulam. The results are summarized as follows : 1. Glue line has no effect on fracture strength. 2. There is a definite interaction between fracture toughness $K_I$ and $K_{II}$ during the mixed mode fracture of glulam. Several criterions for mixed mode failure were compared. The criterion was expressed in the following form: $(\frac{K_I}{K_{IC}})^2+(\frac{K_{II}}{K_{IIC}})^2=1$ 3. As crack inclination increases, $K_{IC}$ value and $K_{IIC}$ value decreases. The equations relating crack angle to $K_{IC}$ and $K_{IIC}$, respectively, were obtained as follows; $K_{IC}$ = -77.42${\gamma}$+153.72 ($R^2$ = 0.78) $K_{IIC}$ = -9.17${\gamma}$+34.90 ($R^2$ = 0.48)

• International Journal of High-Rise Buildings
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• v.7 no.4
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• pp.299-311
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• 2018

As engineered timber such as Glulam is seeing increasing use in tall timber buildings, building codes are adapting to allow for this. In order for this material to be used confidently and safely in one of these applications, there is a need to understand the effects that fire can have on an engineered timber structural member. The post-fire resilience aspect of glulam is studied herein. Two sets of experiments are performed to consider the validity of zero strength guidance with respect to short duration fire exposure on thin glulam members. Small scale samples were heated in a cone calorimeter to different fire severities. These samples illustrated significant strength loss but high variability despite controlled quantification of char layers. Large scale samples were heated locally using a controlled fuel fire in shear and moment locations along the length of the beam respectively. Additionally, reduced cross section samples were created by mechanically carving a way an area of cross section equal to the area lost to char on the heated beams. All of the samples were then loaded to failure in four-point (laterally restrained) bending tests. The beams that have been burnt in the shear region were observed as having a reduction in strength of up to 34.5% from the control beams. These test samples displayed relatively little variability, apart from beams that displayed material defects. The suite of testing indicated that zero strength guidance may be under conservative and may require increasing from 7 mm up to as much as 23 mm.

• Journal of the Korean Wood Science and Technology
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• v.45 no.4
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• pp.409-418
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• 2017

This work attempted to manufacture glued-laminated timber (Glulam) bonded with melamine-urea-formaldehyde (MUF) resin adhesives at various melamine contents from 20% to 50% under high frequency (HF) heating for a very short time. Two preparation methods were employed to prepare MUF resin adhesives with different melamine contents: one-batch method of synthesizing MUF resins in a single batch, and two-batch method of mixing urea-formaldehyde (UF) resin with melamine-formaldehyde (MF) resin that had been synthesized separately. As the melamine content increased, the gelation time and peak temperature of MUF resins decreased. The adhesion performance of plywood showed that the one-batch MUF resin adhesive with 50% melamine content only satisfied the standard requirement of water resistance. Thus, the one-batch MUF resin adhesive with 50% melamine content was applied for bonding wood lamina from four softwood species such as Japanese larch, Korean red pine, Korean pine and Japanese cedar to manufacture Glulam under HF heating. All Glulam samples bonded with the one-batch MUF resin adhesives with 50% melamine content except those from Korean Red Pine satisfied the requirement in water soaking or boiling water delamination test as an exterior grade Glulam. The presence of rosin in Korean Red Pine was believed to be responsible for its poor adhesion. These results showed that the one-batch MUF resin adhesives with 50% melamine content provided acceptable water resistance with exterior grade Glulam manufactured under HF heating.

• Journal of the Korean Wood Science and Technology
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• v.44 no.1
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• pp.67-74
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• 2016

The yield shear strength of bolt connection in glass fiber reinforced glulam was predicted using a design-based equation, and was compared to the empirical yield shear strength. For the predicted equation, the mechanical properties of member (the elastic modulus, Poisson's ratio, shear modulus) was tested. The fracture toughness factor ($K_{ft}$) of glass fiber reinforced glulam was reflected to the revision of the design equation of bolted connection. The compressive strength properties to grain direction was influenced by annual ring angle and width of lamina. Compared with the revised yield shear strength of reinforced glulam, it was tended to be similar to the empirical yield shear strength on the diameter of bolt and the reinforcements. The revised yield shear strength from proposed formula of KBC was most appropriately matched in the bolt connection of the glass fiber reinforced glulam.

• Journal of the Korean Wood Science and Technology
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• v.41 no.1
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• pp.51-57
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• 2013

In order to know the shear performances of a bolted connection in reinforced glulam depending upon the combination of textile glass fiber, a tensile-type shear test was conducted. Textile glass fiber was used as a reinforcement, whose glass fiber arrangement was a plain weaving type or a diagonal cloth type. Reinforced glulam was made up of 5 plies and it was produced by inserting and laminating the plies between laminas depending upon a changed insert position and combination form of textile glass fiber. Tensile-type shear test specimens were a steel plate insert-type and joined at end-distance 7D with bolts whose diameter 12 or 16 mm. In textile glass fiber reinforced glulam, whose volume ratio was 1%, the yield shear strength of a 12 mm bolted connection increased by 10% when a test specimen had reinforced internal layers than when external layers were reinforced. As for textile glass fiber reinforced glulam, whose volume ratio was 2%, the yield shear strength of a 12 mm bolted connection increased significantly by about 22% compared to the bolted connection of non-reinforced glulam, and the yield shear strength of a 16 mm bolted connection was improved by about 20% compared to the bolted connection of non-reinforced glulam.

• Journal of the Korean Wood Science and Technology
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• v.36 no.4
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• pp.19-25
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• 2008

This study was carried out to investigate the bending strength properties of the unreinforced glulam beams and the GFRP laminated glulam beams according to the volume ratio of GFRP. The 7-layer glulam beams ($10cm(b){\times}14cm(h){\times}180cm(l)$) were manufactured, using Larch (Larix kaempferi Carr.) laminae ($2cm(h){\times}10cm(b){\times}360cm(l)$), which were dried to the moisture content of 8% and specific gravity of 0.54. GPRP of 0.1 and 0.3 cm was reinforced between the outmost layer of bottom and next layer. When the glulam beams were reinforced with GFRP at the volume ratio of 0.7% and 2.1%, respectively, the bending strength was increased by 12% and 28%, respectively, in the reinforced beams than in control glulam beams. Also, the GFRP reinforced layer of the glulam beams with GFRP laminations blocked the progression of rupture, and the unbroken part held about 90% of the bending strength. In the results of glue joints test, the block shear strength is higher than $7.1N/mm^2$, the standard of KS F3021, and in the result of delamination, the adhesive strength is good as the water soaking and boiling delamination was less than 5%.

• Journal of the Korean Wood Science and Technology
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• v.28 no.1
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• pp.8-17
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• 2000

Structural glued laminated timbers were manufactured from Japanese larch(Larix leptolepis) lumber. The effect of various factors, such as finger joint, strength of lamination, on the strength properties of glulam was investigated. When only MOE of lamina was used as input variable for the estimation of strength properties of glulam, the deviations between actual and simulated results were increased with the number of lamination, because the effects of variance of lamina properties on the strength estimation of glulam were cumulated with the number of lamination. Therefore, to estimate the MOR of glulam more careful approach was needed. Besides, both MOE and MOR of lamination were used as input variable to compare the effect of input variable. In the case of finger jointed lamination was located in tension zone, MOE of glulam was some effected, because of the variation of MOE of lamination and the deficiency of information for knot. In the case of finger jointed lamination wasn't located in tension zone, more exact estimation was possible than the case of finger jointed lamination was located in tension zone. From the results, it was concluded that more exact estimation of strength properties of glulam could be obtained by considering effects of both finger joint and knot.

• Journal of the Korean Wood Science and Technology
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• v.37 no.1
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• pp.48-55
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• 2009

In the glulam beam deflection it is necessary to check the reliability of theory formula, because of wood anisotropy and wood qualities (knot, slop of grain). In this experiment, when bending stress occurred on glulam, practice deflection of glulam measuring with AICON DPA-Pro 3D system were compared with prediction deflection calculated as substituting MOE through non-destructive testing and static MOE through bending test in differential equation of deflection curve. MOE using ultrasonic wave tester of laminae, MOE using natural frequencies of longitudinal vibrations ($E_{cu}$, $E_{cf}$), MOE using ultrasonic wave tester of glulam ($E_{gu}$) and MOE using natural frequencies of longitudinal vibrations ($E_{gf}$) were substituted in this experiment. When practice deflection measured by 3D system was compared with prediction deflection calculated with differential equation of deflection curve, within proportional limit the ratio of practice deflection and prediction deflection was similar as 1.12 and 1.14, respectively. Deflection using ultrasonic wave tester was 0.89 and 0.95, Deflection using natural frequencies of longitudinal vibrations was 1.07 and 1.10. The results showed that prediction deflection calculated by substituting using non-destructive MOE of glulam having anisotropy in differential equation of deflection curve was agreed well with practice deflection.

• Journal of the Korean Wood Science and Technology
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• v.31 no.5
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• pp.65-71
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• 2003

In this paper, bending capacities of glulams with different configurations of cross-section were evaluated. These configurations included horizontal(BH), vertical(BVN), vertical with vertical plywood (BVV) and vertical combination of lamination with horizontal plywood(BVH). Full-scale bending tests were performed to investigate the effect of different section configurations on bending strength(MOR) and stiffness(MOE) of glulam. Compared with type BH, MOR of glulam with type BVN configuration was improved about 23%, which was considered to be caused by defect dispersion effect, while MOE of glulams with these two types of configurations were similar. Because MOE of plywood is generally smaller than that of solid wood laminar, MOE of type BVH glulam decreased about 15%, but in the case of type BVV glulam, MOR was improved without any reduction of MOE. The reason of this result could be undersood in the view of shear-reinforcement effect, which was verified from analysis of fracture mode. From the results of this study, it was concluded that bending capacity of glulam could be improved by proper section design, such as laminar arrangement and shear reinforcement.

• Journal of the Korean Wood Science and Technology
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• v.38 no.5
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• pp.399-404
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• 2010

A new green home designed to save money while at the same time saving the environment with some of the finest green features available in the market. Composite column composed of structural steel and structural glued laminated timber is avery Eco-friendly building products for design building because that use recycled or second hand. For compare to compressive strength of structural glued laminated timber (glulam), structural steel, and composite column (steel-glulam), tested compressive strength of each specimen. 1) structural glued laminated timber : Theoretical compressive strength is 151.6 kN similar to elastic limits. 2) structural steel (H type) : Theoretical compressive strength is 148.2 kN little under the elastic limits. 3) structural steel (D type) : Theoretical compressive strength is 147.3 kN upper than the elastic limits. 4) composite column : Actual elastic limits are about 600 kN. Result in, composite column improve compressive strength of Structural steel column and provide structural stability of the building.