[논문]Evaluation of Withdrawal Resistance of Screw-Type Fasteners Depending on Lead-Hole Size, Grain Direction, Screw Size, Screw Type and Species

LEE, Hyung Woo; JANG, Sang Sik; KANG, Chun-Won

doi:10.5658/wood.2021.49.2.181

Evaluation of Withdrawal Resistance of Screw-Type Fasteners Depending on Lead-Hole Size, Grain Direction, Screw Size, Screw Type and Species 원문보기

목재공학 = Journal of the Korean wood science and technology, v.49 no.2, 2021년, pp.181 - 190

LEE, Hyung Woo (Department of Bio-based Materials, College of Agriculture & Life Science, Chungnam National University) , JANG, Sang Sik (Department of Bio-based Materials, College of Agriculture & Life Science, Chungnam National University) , KANG, Chun-Won (Department of Housing Environmental Design, and Research Institute of Human Ecology, College of Human Ecology, Jeonbuk National University)

Abstract ▼ AI-Helper

Screw-type fasteners are widely used to make connections between wood members or between wood and steel connectors because they can tolerate the applied loads by withdrawal or shearing. In this study, we evaluated the withdrawal resistances of the screw-type fasteners and analyzed the effects of the lead-hole size, relative grain direction (tangential, radial, and cross-sections) of the wood member, screw diameter, screw type, and species. Two wood species, including domestic larch and imported spruce, and three screw-type fasteners, including domestic lag screws (diameters of 9.46, 7.79, and 6.27 mm), domestic tapping screw (diameter, 6.3 mm), and imported Sherpa screw (diameter, 8.0 mm) were used. To assess the effect of lead-hole size, the lead holes with diameters corresponding to 68.7%, 70.8%, and 74.0% of the shank diameter of the lag screw were predrilled. The lead hole corresponding to 74% of the shank diameter was selected for this study because the smaller lead holes required higher rotational force for installation, which may cause damage in the screw neck, although there was no significant difference in the withdrawal resistance depending on the lead-hole sizes applied in this study. The lag screws installed on the tangential and radial surfaces showed similar withdrawal resistances to each other, which were greater than those installed on the cross-sectional surface. As the lag screw diameter increased from 6.27 mm to 9.46 mm, the withdrawal resistance also increased proportionally. The withdrawal resistance of the tapping screw having a diameter of 6.3 mm was almost 1.6 times higher than that of the lag screw having a similar diameter of 6.27 mm, while that of Sherpa screw having a diameter of 8.0 mm was around 1.4 times higher than that of the lag screw having a similar diameter of 7.79 mm.

주제어

표/그림 (18)

그림 Fig. 1. Shape of the wood specimen (larch, spruce) used for the withdrawal tests.
그림 Fig. 2. Screw-type fasteners used in this study: lag screw (diameter = 7.79 mm), tapping screw, and Sherpa screw from the left.
표 Table 1. Dimension of the fasteners used in this study
그림 Fig. 3. Specification for the specimen symbol used in this study.
표 Table 2. Details of lead-hole size specimens
표 Table 3. Details of the lag screw specimens
표 Table 4. Details of tapping and Sherpa screw specimens
그림 Fig. 4. Schematic diagram (a) and the actual photo (b) of the testing arrangement used for the withdrawal resistance test of screw-type fasteners in accordance with KS F ISO 9087.
그림 Fig. 5. Load-displacement diagrams obtained from the withdrawal-resistance test for the lag screws showing the effects of the lead-hole size.
표 Table 5. Withdrawal resistance depending on the lead-hole size
표 Table 6. Withdrawal resistance of lag screws depending on the grain direction
그림 Fig. 6. Comparison of the test results for the lag screws installed on the side grain with those given in NDS (larch).
그림 Fig. 7. Comparison of the test results for the lag screws installed on the side grain with those given in NDS (spruce).
표 Table 7. Withdrawal resistances of lag screws
표 Table 8. Reference withdrawal value for the lag screws given in NDS (2018) (unit: N/mm)
그림 Fig. 8. Comparison of the test results for the lag screw (6.27mm diameter) installed in larch with those for the tapping screw (6.3mm diameter).
그림 Fig. 9. Comparison of the test results for the lag screw (7.79mm diameter) installed in larch with those for the Sherpa screw (8.0mm diameter).
표 Table 9. Result of withdrawal-resistance for tapping screw and Sherpa screw

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문제 정의

screw in the construction site. To overcome this problem by finding the way to install the lag screw easily, the effect of one lead-hole size on the withdrawal resistance of lag screw was studied in this study. And also the effect of species, grain direction, screw size, lead-hole size and screw type (lag screw, tapping screw, Sherpa screw) on the withdrawal resistance were studied, and the results of the tests were compared with the values calculated by using the equation given in NDS (2018) and KBC (2016).

제안 방법

In this study, the withdrawal resistances of the screw-type fasteners including domestic lag screws (diameters of 9.46 mm, 7.79 mm and 6.27 mm), domestic tapping screws (diameter 6.3 mm) and imported Sherpa screws (diameter 8.0 mm) were tested to evaluate the effects of lead-hole size, grain direction, species of main member and screw diameter. Sawn and dried lumber of domestic larch and imported spruce were used as main members and the withdrawal tests were performed in accordance with KS F ISO 9087 for tangential, radial and longitudinal directions.
Tapping screw and Sherpa screw are usually installed without the pre-drilled lead-hole. The tapping and Sherpa screws were tested on larch, and the effect of the grain direction (S, C) was evaluated. Details of the specimens for the tapping and Sherpa screws are given in Table 4.
The withdrawal resistances in the grain direction of tangential and radial were higher than that in the longitudinal direction but similar to each other. Therefore, the withdrawal tests were performed in the direction of side grain, which is mixed of tangential and radial, and end grain (longitudinal direction) without distinguishing between tangential and radial direction.
7 mm), which caused the breakage of the neck during the test for some specimens. To avoid the large rotational forces that might cause the breakage of the neck, the lead-hole size corresponding to 74% of the screw shank diameter was employed through the rest of the tests in this study. Even though the lead-hole size corresponding to 60~70% of the screw shank be recommended for the wood member having the specific gravity between 0.

대상 데이터

2. Screw-type fasteners used in this study: lag screw (diameter = 7.79 mm), tapping screw, and Sherpa screw from the left.
2 were used in this study. The diameter of the fasteners used in this study were 9.46 mm, 7.79 mm and 6.27 mm for the lag screw, 6.3 mm for the tapping screw, and 8.0 mm for Sherpa screw. The total length of the fasteners were 130.
Three types of fasteners (lag screw, tapping screw and Sherpa screw) as shown in Fig. 2 were used in this study. The diameter of the fasteners used in this study were 9.

이론/모형

0 mm) were tested to evaluate the effects of lead-hole size, grain direction, species of main member and screw diameter. Sawn and dried lumber of domestic larch and imported spruce were used as main members and the withdrawal tests were performed in accordance with KS F ISO 9087 for tangential, radial and longitudinal directions.
The withdrawal-resistance tests were performed in accordance with KS F ISO 9087. To measure the withdrawal resistance of the screw-type fasteners under pulling load, the testing arrangement as shown in Fig.

성능/효과

For the whole tests, the number of replication was 10, and 5 percentile (5% lower exclusion limit) was calculated based on the assumption of normal distribution of the test results, and the allowable withdrawal load was calculated by dividing the 5 percentile by the safety factor of 2.0.
Through the withdrawal tests with the specimens having different lead-hole sizes, it was concluded that the lead-hole corresponding to 74% of the shank diameter of the lag screw was appropriate for this study because the smaller lead-holes required higher rotational force for installation which may cause damage in the screw neck even though there was no significant difference in the withdrawal resistance depending on the lead-hole sizes applied in this study. The withdrawal resistances in the grain direction of tangential and radial were higher than that in the longitudinal direction but similar to each other.

참고문헌 (11)

Ahn, K.S., Pang, S.J., Oh, J.K. 2021. Prediction of withdrawal resistance of single screw on Korean wood products. Journal of the Korean Wood Science and Technology 49(1): 93-102.

원문보기 상세보기
American Forest & Paper Association and American Wood Council. 2018. National Design Specification for Wood Construction (NDS).
Architectural Institute of Korea (AIK). 2016. Korean Building Code (KBC) and Commentary, Kimoondang, Seoul, Korea.
Cha, J.K. 2011. Predicting the withdrawal load of wood screws in domestic wood by screw diameter, depth of penetration and specific gravity of wood. Journal of the Korean Wood Science and Technology 39(3): 252-257.

원문보기 상세보기
Cha, J.K. 2012. Effect of the withdrawal strength of wood screws in domestic wood by shear strength with different growth ring orientation. Journal of the Korean Wood Science and Technology 40(6): 363-369.

원문보기 상세보기
Cha, J.K. 2016. The effect of diameter and prehole clearance for wooden dowel on the withdrawal loads of domestic wood. Journal of the Korean Wood Science and Technology 44(5): 736-742.

원문보기 상세보기
Korea Standard Association: Determination of nail and screw holding power under axial load application for wood. KS F ISO 9087, 2014.
Korea Standard Association: Determination of moisture content of wood. KS F 2199, 2016.
Korea Standard Association: Determination of density and specific gravity of wood. KS F 2198, 2016.
Kim, S.C. 1979. Studies on the static withdrawal resistance on nail in wood. Journal of the Korean Wood Science and Technology 7(1): 8-11.
Oh, S.C. 2013. Withdrawal and lateral resistance of nail joints composed of dimension lumber and OSB in light-frame wood construction. Journal of the Korean Wood Science and Technology 41(3): 211-220.

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