• Journal of the Korean Wood Science and Technology
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• v.41 no.2
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• pp.158-163
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• 2013

Cross laminated timber (CLT) has been an rising issue as a promising building material replacing steel-concrete in mid story rise construction. But, there was no specific standard for CLT because it had been developed in industrial section. Recently, new draft for requirements of CLT was proposed by EN which suggested to evaluate the performance of adhesive in CLT by the same method as glulam. But, it has been reported that shear performance of cross laminated timber is governed by rolling shear. Therefore, block shear tests were carried out to compare parallel to grain laminating and cross laminating using commercial one component PUR (Poly urethane resin). The result showed that the current glulam standard for evaluating bonding performance is not appropriate for CLT. Beacause shear strength of cross laminating decreased to 1/3 of parallel to grain laminating and this strength was representing shear performance of wood itself not the bond. However, cross laminating showed no significant effect on wood failure. Thus, wood failure can be used as a requirement of CLT bonding. Based on the results, cross laminating effect should be included when evaluating adhesive performance of CLT correctly and should be considered as an important factor.

• Journal of the Korean Wood Science and Technology
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• v.47 no.1
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• pp.40-50
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• 2019

The aim of this study was to investigate the effects of density, temperature, size, and grain direction on measurement of moisture contents (MC) of wood materials non-destructively. The MC of different sizes of solid wood, glulam, and CLT from larch (larix kaempferi, $560kg/m^3$) and pine (pinus koraiensis, $430kg/m^3$) were measured using the dielectric type and resistance type meters. The specimens were conditioned in the environmental chamber to be equilibrium moisture content (EMC) of 12 % and 19 %. When density setting in dielectric type meter was increased from $400kg/m^3$ to $600kg/m^3$, the MCs of specimen (S-L-100-E) were decreased from 13.4 % to 11.3 %. However, when wood group (WG) setting in resistance type meter was changed from WG1 to WG4, the measured MCs were increased from 9.2 % to 12.3 %. When temperature setting in resistance type meters was changed from 0 to $35^{\circ}C$, the MC was decreased from 17.0 % to 13.0 %. The MCs measured by dielectric type meter for larger specimens (S-L-100-E_11.3 %, G-L-240-E_11.7 % and C-L-120-E_12.8 %) were higher than those of small size specimens (S-L-30-E_8.7 %, G-L-150-E_10.3 %, and C-L-90-E_9.7 %). The MCs measured by resistance type meter for larger specimens (G-L-240-E_11.6 % and C-L-120-E_13.3 %) were also higher than those of small size specimens (G-L-150-E_10.4 %, and C-L-90-E_11.8 %). The resistance type meter was not affected by the grain direction but the dielectric type meter were affected by the grain direction. The MC measured by resistance type meter for G-L-120-E perpendicular to grain direction was 11.5 % and the measured MC parallel to grain direction was 11.3 %. The MC measured by dielectric type meter parallel to grain direction (12.1 %) was higher than that measured perpendicular to grain direction (10.7 %).

• Journal of the Korea Furniture Society
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• v.24 no.4
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• pp.426-432
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• 2013

Fire resistance and impact sound insulation tests were performed for a floor assembly, of which stiffness was reinforced by shortening the span of floor joists by installing glulam beam additionally in the middle or one thirds of the original span, and which an additional ceiling component was installed apart from floor structure. By applying the isolated ceiling, timber framed floor showed 1 hour of fire resistance even in case that dead load was increased by considering cement mortar layer for radiant floor heating. Insulation performance against light and heavy impact sound was improved significantly by applying the sound absorbing layer of big mass and high elasticity in addition to the stiffness improvement and isolated ceiling.

• Journal of the Korean Wood Science and Technology
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• v.48 no.6
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• pp.791-806
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• 2020

In this study, a block shear strength test was conducted to compare and analyze the strength and failure mode on the glued laminated timber, CLT, and Ply-lam CLT, which are mainly used for the construction of wood construction as engineering wood. Through this, the Ply-lam CLT manufacturing conditions for optimum production, such as the type of lamina, plywood, adhesive, and layer composition, were investigated. The results are as follow. Through block shear strength test, it showed high strength in the order of glued laminated timber, Ply-lam CLT and CLT. In particular, the shear strength of Ply-lam CLT, which is made of a composite structure of larch plywood and larch lamina, passed 7.1 N/㎟, which is a Korean industrial standards for block shear strength of structural glued laminated timber. In addition, in this study, there was no different in shear strength according to the adhesive type used for glulam, CLT, and Ply-lam CLT adhesion. However, in the case of Ply-lam CLT, the difference in shear strength of Ply-lam CLT was shown according to the type of lamina and plywood. The results showed high strength in the order of Larix kaempferi > Mixed light hardwood ≒ Pinus densiflora, sieb, et, Zucc plywood. The optimal configuration of Ply-lam CLT is when larch plywood and larch lamina are used, and it is decided that the adhesive can be used by selecting PRF and PUR according to the application. The results of block shear strength failure mode by type of wood based materials were analyzed. The failure mode showed shear parallel-to-grain for glulam, rolling shear for CLT, and shear parallel-to-grain and rolling for ply-lam CLT. This is closely related to shear strength results and is decided to indicate higher shear strength in Ply-lam CLT than in CLT due to rolling shear.

• Journal of the Korean Wood Science and Technology
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• v.44 no.1
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• pp.40-47
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• 2016

Instead of metal connector generally used on the structural glued laminated timber rahmen joints, the GFRP reinforced laminated plates combining veneer and GFRP (Glass Fiber Reinforced Plastic) and bonded type GFRP rod were used as the connectors. As a result of moment resistance performance evaluation on the joint part applied with these connectors, the yield moment of specimen using the GFRP reinforced laminated plates and GFRP rod pin was measured 4 % lower in comparison to the specimen (Type-1) using the metal connectors, but the initial rotational stiffness was measured 29% higher. Also, the yield moment and rotational stiffness of the specimen using the GFRP-reinforced laminated plates and wood (Eucalyptus marginata) pin showed were measured 11% and 56% higher in comparison to the Type-1 specimen, showing the best performance. It was also confirmed through the failure shape and perfect elasto-plasticity analysis that it showed ductility behavior, not brittle fracture, from the shear resisting force by the pin and the bonding strength increased and the unification of member was carried out. On the other hand, in case of the specimen bonded with GFRP rod, it was impossible to measure the bonding performance or it was measured very low due to poor bonding.

• Journal of the Korean Wood Science and Technology
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• v.43 no.4
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• pp.463-469
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• 2015

In this study, to improve bending strength performance of Korean white pine, we made the curved composite glulam that was reinforced with glass fiber materials and larch lamina. Five types of Korean white pine curved glulams were made depending on whether they had been reinforced or not and how they had been reinforced. Type-A, reference specimen, was produced only with Korean white pine lamina, and Type-B was with larch lamina in the same thickness. Type-C was made by inserting a glass fiber cloth of textile shape between the each layer. Type-D was reinforced with two glass fiber cloths, which were placed inside and outside of the outermost lamina. Type-E was reinforced with GFRP sheet in the same way as Type-D. As a result of this bending strength test, the modulus of rupture (MOR) of Type-B, Type-C and Type-E were increased by 29%, 6%, and 48% in comparison with Type-A. However, MOR of Type-D was decreased by 2% in comparison with Type-A. In the failure modes, Type-A, Type-B and Type-C were totally fractured at the maximum load. However, load values of Type-D and Type-E decreased slowly because of reinforcement of fracture suppression, and the GFRP sheet (Type-E) had better reinforcing effect on compressive stress and tensile stress than the glass fiber cloth (Type-D).

• Journal of the Korean Wood Science and Technology
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• v.42 no.3
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• pp.282-289
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• 2014

After being laminated with a combination of glass fiber reinforced plastic and plywood, the GFRP laminated plate was densificated for 1 hour at $150^{\circ}C$ with pressure of $1.96N/mm^2$. A partial reinforced beam was produced by attaching the 5 GFRP laminated plates to the joint of glulam and the column. In addition, the column to beam joint was produced by using reinforced laminated wooden pin which was made of GFRP sheet and plywood, fiber glass reinforced cylindrical-LVL column. The joint was made of round log, glulam and drift pin as the reference specimen, and its moment resistance was evaluated. As a result, the strength performance of specimens with partial reinforced beams were 1.8 times stronger than the reference specimen on average. Furthermore, rupture was neither occurred on partial reinforced beam nor column. Toughness and stiffness of joints were also fine. The GFRP sheet reinforced laminated plate showed better reinforcement effect than GFRP textile reinforced one. GFRP sheet was inserted into each layer of laminate, and it showed good condition in rotation-angle and strength, therefore it is the most appropriate to reinforce the part of the beam.

• Journal of the Korean Wood Science and Technology
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• v.33 no.1 s.129
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• pp.7-16
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• 2005

This study was carried out to evaluate the structural property of double shear bolted connections in Korean Larch. For the main member, sawn lumber and Glulam were used in which thickness of lumber is 39 mm, 89 mm, 139 mm, 189 mm and Glulam 80 mm, 140 mm, 170 mm. For the side member, sawn lumber and steel plate were used in which thickness of lumber is the same of the main member and steel plate is 6mm. And connections were jointed by M12, M16, M20 bolts which were usually used for wood constructions in Korea. Directions of loading to connections were perpendicular and parallel to grain of main and side member. First, through the dowel bearing test, the dowel bearing strength was evaluated and through the bolt bending tests, the bolt bending strength was evaluated. And then experiments for the connection were performed. Obtained results from experiments were compared with calculated values by EYM and analyzed. Strength of double shear bolted connections in Korean Larch was similar or higher than calculated value by EYM. Especially when the side member was made by the sawn lumber, it was similar to the calculated value. In failure mode, the mode was effected by the knot and the dry defect. In the thin main member, it was shown mode I and as the thickness of the main member was thicker, it was changed into mode III.

• Journal of the Korean Wood Science and Technology
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• v.43 no.5
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• pp.682-690
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• 2015

The bonding performance of two types of wood adhesives, namely phenol-resorcinol-formaldehyde (PRF) resin and melamine-urea-formaldehyde (MUF) resin for glued laminated timber manufactured by high frequency (HF) heating was evaluated. The HF heating system consists of HF oscillator with dielectric heating system for curing adhesives, and hydraulic press system for clamping glued laminated timber. The designed frequency and output power of the HF system was as 5 MHz and 60 kW, respectively. To verify dielectric heating mechanism under HF oscillation, the heat loss factors of laminae and adhesives were measured. The results show that it is possible to selectively heat adhesives for their curing due to the remarkably higher loss factor of the adhesives than those of wood laminae. The temperature of adhesive in the bonding line reached up to the set temperature within a few seconds by high frequency oscillating, which advanced the curing of adhesive afterwards. The bonding performance, such as shear strength of bonding line, water soaking delamination, and boiling water soaking delamination of PRF resin met the requirement of Korean Standard (KS), however the MUF resin did not meet the KS requirement of boiling water soaking delamination. These results indicate that the HF heating system is successful to manufacture glued laminated timbers with PRF resins to meet the bonding requirements.

• Journal of the Korean Wood Science and Technology
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• v.36 no.4
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• pp.66-76
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• 2008

Recently, demands for the structural uses with domestic Japanese larch and SPF(spruce-pine-fir) lumber from North America have been increased. Shear properties of nailed joints that are the most simple and optimum fastening method in wooden constructions, especially in light frame construction. For the nailed joints, in North America and Japan, a number of basic and practical studies have been performed. The shear behaviors for the double nailed joint with variations of member and its direction, were examined. Shear properties of the shear specimens with SPF stud showed more remarkable variation than larch glulam and larch stud. Furthermore, the relationships between slip modulus and strength are not coincided in every case.