A Study on the Block Shear Strength according to the Layer Composition of and Adhesive Type of Ply-Lam CLT(Ply-Lam CLT의 층재 구성 및 접착제 종류에 따른 블록전단강도에 관한 연구)

( Gyu Woong Choi ),( Seung Min Yang ),( Hyun Jae Lee ),( Jun Ho Kim ),( Kwang Hyeon Choi ),( Seog Goo Kang ) 한국목재공학회 2020 목재공학 Vol.48 No.6

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/mm², 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.

국산재 합판을 코어재로 사용한 교차집성재(CLT) 적용 목조주택의 냉·난방에너지 요구량 분석

장성진,위승환,이종기,이화영,조현미,김수민 한국생활환경학회 2017 한국생활환경학회지 Vol.24 No.6

Cross-laminated timber (CLT) is a structural timber developed for low-grade timber utilization. This studyanalyzed the thermal properties of Ply-lam CLT using Korean plywood as a core material of CLT and analyzed thecooling and heating energy demands of wooden house with Ply-lam CLT. The thermal conductivity of Ply-lam CLTwas measured by TCi thermal conductivity measurement equipment. The overall thermal conductivity of the five-layerPly-lam CLT was calculated using KS M ISO 6946. The cooling and heating energy demands of the wooden houseswith Ply-lam CLT were analyzed using Passive House Planning Package (PHPP), a building energy analysis programbased on ISO 13790. The thermal conductivity of Ply-lam CLT was lower than that of existing CLT consisting offive-layered larch. In addition, it was confirmed that the heat insulating performance of CLT can be further improvedaccording to the application site and thickness of the plywood board. The CLT applied wall reduces the cooling andheating energy demands because of reduce the thermal bridge and infiltration in the wall. Finally, considering both theamount of cooling and heating energy demand reduction and the wall thickness increase, it is considered that the wallwith the passive house level (0.15 W/m2K) applied the Ply-lam CLT board is most suitable among 7 wall cases.

Communicative Language Teaching and Second Language Acquisition : Are They Bedfellows?

김한길 한국사회언어학회 2022 사회언어학 Vol.30 No.2

The advent of CLT in the 1980s led to the CLT-SLA debate which continued unabated for the last forty years. This paper asks, Does the now dominant Communicative Language Teaching (CLT) promote Second Language Acquisition (SLA)? In addressing this question, the paper first reviews and explains the social academic history of CLT; different versions of CLT (strong, weak); how CLT operates; its relationship to SLA, such as perceptions of SLA that have contributed to the development of CLT pedagogy (communicative competence, input, output, interaction hypothesis); and techniques used in CLT. Next, it deliberates on the most controversial issues of the CLT-SLA debate, including language forms, corrective feedback, teachers' perceptions of and approaches to CLT, and classroom conditions, followed by a discussion of the ease/difficulty of implementing CLT. It concludes with a discussion of how teachers can best practice CLT in their classrooms.

Effects of combinations of lamina grade and thickness, and span-to-depth ratios on bending properties of cross-laminated timber (CLT) floor

Pang, Sung-Jun,Jeong, Gi Young Elsevier 2019 Construction and Building Materials Vol.222 No.-

<P><B>Abstract</B></P> <P>The aim of this study was to investigate effects of wood species, thickness and lamina combinations, and span-to-depth ratio ( <SUB> R sd </SUB> ) on bending strength and stiffness of cross-laminated timber (CLT) floor element. CLTs with three different thickness (90 mm, 120 mm, and 150 mm) were manufactured using two species, larch and pine. <SUB> R sd </SUB> was 12:1 for shear specimens and 24:1 for bending specimens. Four-point bending test was carried out in accordance with prEN 16351. The higher density species (larch) CLT showed higher load resistance with larger span length. The load resistances of larch CLT was 1.2 times higher than pine CLT. The maximum span length of larch CLT was 1.1 times longer than pine CLT. As the thickness of CLT was increased, load resistance and span length were also increased. When the thickness of CLT was increased from 90 mm to 150 mm, load resistances was increased by approximately 308% for larch and 310% for pine, and span length was increased by approximately 90% for larch and 89% for pine.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Ultimate and serviceability limit state design of CLT were evaluated. </LI> <LI> Effect of lamina combination on moment and deflection properties of CLT were analyzed. </LI> <LI> Bending properties were characterized by gamma, shear analogy, and isotropic models. </LI> <LI> Span limit by deflection of CLT made from different lamina combination was analyzed. </LI> <LI> Failure and bending properties of CLT associated with different spans were found. </LI> </UL> </P>

합판을 코어로 활용한 CLT의 단열성능개선에 관한 연구

김경중,양승민,김준호,최규웅,강석구 한국가구학회 2018 한국가구학회지 Vol.29 No.4

By using the thermal conductivity and temperature gradient for each type of structural wood materials using larches, this study calculated the heat conduction (Qc). Through this, the potential insulation improvement of structural material was verified. Furthermore, by fabricating a cross-laminated timber (CLT) using conventional insulators such as gypsum board and sound-absorbing board, the insulation performance improvement effect was investigated based on the heat conduction, and the optimal ratio of cross lamination was derived. In the result of measuring the temperature gradient of upper and lower parts of structural wood materials, the plywood-core CLT showed about 10°C higher temperature gradient than the laminated wood and CLT under a same condition. This means that the plywood-core CLT has better efficiency of using energy than other wood materials. Through this, it is determined that effect of economic efficiency improvement can be expected with respect to heating and cooling if plywood-core CLT is used as a wall. Six types of plywood-core CLT with high-insulation property, in which the gypsum and sound-absorbing insulators were cross-laminated in a certain ratio, showed lower heat conduction than the laminated wood, CLT, and plywood-core CLT. Particularly, the gypsum board-inserted plywood-core CLT (27.6% gypsum) showed the lowest heat conduction of about 0.6 W. This result was 35.8% lower thanthat of larch-laminated wood, 36.4% lower than that of CLT, and about 40% lower than that of plywood-core CLT. Through these results, it is determined that the insulator-inserted wood material can be used as a substitute for conventional walls of internal insulation structure.

A Study on Floor Impact Sound Insulation Performance of Cross-Laminated Timber (CLT): Focused on Joint Types, Species and Thicknesses

하연수,이효진,이상준,신진애,송다빈 한국목재공학회 2023 목재공학 Vol.51 No.5

In this study, the floor impact sound insulation performance of Korean domestic Cross-Laminated Timber (CLT) slabs was evaluated according to their joint types, species and thicknesses in laboratory experiments. The sound insulation performance of the CLT has not been investigated before, thus, this study was conducted to quantify basic data on floor impact sound insulation performance of CLT slabs. 5-ply and 150 mm thick CLT panels made of 2 species, Larix kaempferi and Pinus densiflora, were used for the study. The CLT panels were assembled by 3 types of inter-panel joints to form floor slabs: spline, butt and half-lap. And the 150 mm thick Larix CLT slabs were stacked to the thicknesses of 300 mm and 450 mm. The heavy-weight floor impact sound insulation performance of the 150 mm CLT slabs were evaluated to be 70 dB for the Larix slabs and 71.6 dB for the Pinus slabs, and the light-weight floor impact sound insulation performance, 78.3 dB and 79.6 dB, respectively. No significant difference in the sound insulation performance was found between the slabs of the 2 species or among the 3 types of joints. The reduction of 1 dB in the heavy-weight floor impact sound and 1.6 dB in the light-weight floor impact sound per 30 mm increase in thickness were confirmed through the experiments. This study can be viewed as the basic research for the evaluation of floor impact sound insulation performance of CLT.

강재 전단 연결재가 사용된 CLT-콘크리트 합성바닥판의 휨성능 평가

박금성(Park, Keum-Sung),오근영(Oh, Keunyeong) 대한건축학회 2021 대한건축학회논문집 Vol.37 No.10

The purpose of this study was to evaluate the flexural performance of CLT-concrete composite floors that used steel shear connectors for applying a light modular system. The proposed steel shear connectors are inverted U-shaped and T-shaped, and were installed in the notches of the CLT floor. As experimental variables, the shear connector types, the number and thickness of CLT layers were considered, and the flexural performance of six composite floor specimens was evaluated. As a result, the maximum loads of all specimens were determined by rolling shear fractures and the specimens using the inverted U-shaped shear connector showed excellent flexural performance. However, the composite effect between CLT and concrete was found to be insignificant, and it is considered that it is necessary to improve the shape of steel shear connector later.

공동체적 지역재생을 위한 CLT모델 도입 검토-토지임대부 주택분양제도와의 비교를 중심으로-

조제희 ( Cho Jae-hee ),이승훈 ( Lee Seung-hoon ) 건국대학교 법학연구소 2015 일감부동산법학 Vol.11 No.-

부동산 소유에 따른 부의 불균형 문제를 시정하고 서민을 위한 저렴한 주택을 공급하기 위하여 지난 2009년 제정된 `토지임대부 분양주택 공급촉진을 위한 특별조치법`(토지임대분양주택법)은 공공이 소유한 토지 위에 건설된 주택을 토지분이 제해진 가격으로 공급함으로써 토지공개념의 이념을 일정부분 제도화하려는 시도로 평가할 수 있다. 그러나 현재까지 이 제도에 기초한 주택 분양의 사례는 많지 않고 그 효과의 지속 여부도 불확실하다. 이 연구에서는 미국과 영국에서 토지공개념에 기반하여 저소득계층에게 저렴한 주택을 공급하는 방안인 공동체토지신탁(CLT)의 모델을 참고하여 현행 토지임대부 주택분양제도의 개선·보완책을 찾고자 한다. CLT는 공동체가 소유한 토지에 건설된 주택을 분양하고 분양자에게 토지를 임대한다는 점에서 토지임대부 주택분양제도와 유사한 원리를 채택하고 있다. 그러나 현행 토지임대부 주택분양제도는 토지의 소유 및 분양 사업이 공공 주도의 하향식으로 전개되고 있으며, 분양 이후 지속적으로 주택가격을 안정시킬 수 있는 제도적 방안이 미흡한 반면에, CLT는 지역주민과 시민사회단체의 전문가집단, 지방자치단체 등이 의사결정에 참여하는 공동체적 거버넌스를 갖춘 영구적인 사업조직으로서 분양 이후에도 공동체 원리에 기반한 자율적 규제를 통하여 주택 가격의 안정과 주택의 관리·개선에 성과를 내고 있다. 이러한 점에 착안하여 본 연구에서는 토지임대부 주택분양제도에 대하여 다음과 같은 제도적 보완을 제안한다. 첫째, 사업 목적의 측면에서 단순히 초기 분양가격을 낮추기 위한 기술적 방안으로서의 공공토지소유에 머무르지 말고 토지의 공동체적 향유를 위한 협력의 개념을 도입하여야 한다. 둘째, 사업 주체의 측면에서 공공부문 외에 지역공동체 사업조직을 제도적으로 인정하여야 한다. 영국과 미국의 입법례에서 보듯이 법률에 CLT와 같은 공동체 사업조직을 명문화하고 권한과 책임을 부여하는 방식을 고려하여야 한다. 셋째, 사업 대상과 수요자의 측면에서 저소득층의 주거 안정이라는 명확한 목표 하에 저소득층 밀집지역에 대한 주거복지 사업으로서 접근하여야 한다. 넷째, 분양 이후의 관리·운영에 유의하여야 한다. 지속적인 가격 안정을 위해서 토지임대라는 조건 외에도 해외 CLT의 사례와 같은 환매 조건부 가격 규제 방식이 필요하며 토지 및 주택의 이용·관리·개선에 공동체가 적극적으로 참여할 수 있는 방안을 마련하여야 한다. This study attempts to find a way to improve and/or complement the Community Land Trust model which is widely recognized in the US and the UK as a way to provide affordable housing to the low income based on the concept of land as common property. Under the current law, in the land-leased housing system, land and house supply is managed by the administration unilaterally and lacks a systematic approach in stabilizing the house price and maintaining it at a fair level after the sale of the houses, whereas the CLT model, as a governance involves the local community, professionals and local government in the decision-making process, seems to achieve price stabilization and efficient management and/or improvement even after the sale of the houses. This study proposes the following suggestions for the improvement of the current land-leased housing system based on the above. First, as to the purpose of the project, the system must not stay as a technical measure to lower the initial house prices but further adopt the concept of cooperation towards communal sharing of the benefits arising from land use. Second, as to the operating forces involved, local community organization as well as the public administration must be systematically acknowledged. Third, under the clear purpose of housing stabilization for the low income families, the project must be approached as housing welfare project for the areas where low income families are concentrated. Fourth, emphasis must be given to the management of the land and houses after the sale. For permanent price stabilization, adopting repurchase condition is required, and a way to promote active involvement of the local communities in utilization, management, and improvement of land and houses must be provided.

Second language teacher education: Enhancing teacher training and professional development for CLT

이보영 한국초등영어교육학회 2016 초등영어교육 Vol.22 No.3

Communicative language teaching (CLT) has been developed for decades as the most reliable solution for English language learners to become communicatively competent. However, there have been numerous studies that show that many teachers in an English as a foreign language (EFL) context expressed frustration about not having an accurate understanding of CLT or how to conduct it effectively with fewer opportunities for students to be engaged in meaningful communication. In contrast to studies about the limitations and problems of CLT in Korean education environments, this study revealed that most Korean elementary school English teachers have a fairly accurate understanding of the method, which is sufficient for managing classes using CLT. This study is conducted using quantitative study methodology to investigate teacher perceptions and beliefs in CLT and see how they have been affected by their own CLT learning experiences provided in teacher training programs (TTP). To this end, this study discusses the characteristics of such programs by surveying 94 participants and then interviewing the teachers chosen. It is suggested that diverse venues for the teachers to establish networks should be offered to better implement CLT. Also, long-term and consistent TTPs need to be further developed.

Pre-Service Teachers’ Perspectives on CLT in Korea and Its Practices

조영교 현대영미어문학회 2018 현대영미어문학 Vol.36 No.2

This study examined the features of CLT-orientations and methods for English teaching in Korea and the perceptions of pre-service English language teachers. A total of 24 students participated in a survey where 31 items in open-ended and Likert scale were used to examine the participants’ teaching goals, perceptions on CLT principles and methods and assessment of CLT practices in Korean school settings. The findings show that promotion of CLT at the national level has been consistent over the decades wherein communicative competence has been promulgated as its primary goal. Despite the policy ideal of promoting English competence at all school levels, CLT in its full implementation still seems to be a distal reality for classroom teaching in Korea. Pre-service teachers’ own views on the biggest attribution of such failure were given to the exam-dominant classroom culture that requires sacrifice of communicative goals. Lack of retraining in CLT methods and resources was another line of teacher discourse that accounted for the unstable status quo of CLT in Korea.