柳杉與定向粒片板釘接側向拉伸疲勞行為

The Fatigue Behaviors of Lateral Resistance of Nail Joint between Japanese Cedar and Orineted Strand Board

蘇文清(Wen-Chin Su) ； 王怡仁(Yiren Wang)

《林產工業》 18卷3期 (1999/09) Pp. 279-285

https://doi.org/10.6561/FPI.1999.18(3).8

摘要

鐵釘由於能提供木結構中接合部位適當的強度和挺性，再配合以氣動釘槍的使用，故能快速施工，所以被廣泛的運用於木結構中。本研究利用省產柳杉造林木為主元件而以定向粒片板為側元件施以單一釘接觀測其側向拉伸在靜態與動態的行為。所用釘尺寸有N38和N50兩種，柳杉實木橫斷面為38×89 mm，而定向粒片板有9 mm和12 mm兩種，長均為210 mm。施力方向又依定向粒片板的方向分為平行木理（A）和垂直木理（E）。實驗方式為先將各組合施以靜態載重至破壞，記錄其破壞載重，然後再針對N38的接合施以拉伸疲勞試驗，拉仲疲勞試驗的載重基準為平均靜態破壞載重的60%和70%，載重形式為以載重基準為波峰，零載重為波谷且頻率為3Hz的正弦波。在靜態方面，接合的破壞載重、破壞時的滑動量、及剛性在相同的厚度和方向時，均以N50的接合大於N38的接合。定向粒片板方向的影響在N38接合時較無一致的結果，但在N50的接合則合發現平行木理和垂直木理會出現較明顯的差異，除破壞載重和破壞時的滑動量外，其餘性質均可觀察到平行木理的載重值和剛性值會高於垂直木理的情形。由N50的接合亦可觀察到在足夠釘入深度時側元件板厚的影響不顯著。以N38接合的拉伸疲勞試驗結果顯示在70%載重基準時E12、A12、E9及A9到破壞的疲勞次數分別為69804、89465、54612和56271，而在60%載重基準時則為１87437、127089、100萬及68451。其中E9有80%在到達100萬次後仍未破壞，顯示其疲勞限度載重應在載重基準60%以下。另斷釘處常發生在主元件的柳杉亦顯示木材的側向拉伸中釘子不能假設為懸臂樑的受力情形。

關鍵字

釘 ； 側向拉伸 ； 拉伸疲勞試驗 ； 柳杉 ； 定向粒片板

並列摘要

Nails have been used extensively in wood structure due to their sufficient joint strength and stiffness. In this study, two by four inch domestic Japanese cedar (Cryptomeria japonica) lumber is used as the main member and oriented strand board (OSB) is used as side member jointed by a single box nail to test the static and dynamic behavior in lateral resistance. Two sizes of nail (N38 and N50) are used. Two thickness of OSB of 9 and 12 mm are tested. Two loading direction were considered in parallel and perpendicular to the long axis of OSB. All joints are statically loaded to failure to record their maximum load and other characteristics. The dynamic test was carried out in the joints which were connected by N38 box nail. The load levels are 60% and 70% of the average static maxi-mun load. The load function is a non-reversed 3 Hz sinusodial wave with the load level as its peak value. The fatigue test was carried out until failure occ urred or test cycles reached one million. The maximum static load, slip at failure and stiffness of N50 were always larger than those of N38 under the same side member and orientation. The influence of thickness and orientation of the side member in the N38 joints showed no consistent results. However, the stiffinesses and the loads at 2mm and .381 mm slip of N50 nail joints showed significant larger values of the parallel case than those of the perpendicular case. The cycles to failure for the joint of N38 at 70% load level for E12, A12, E9 and A9 are 69804, 89465, 54612 and 56271, respectively. While at load level of 60%, the cycles to failure are 187437,127089,1 million and 68451. The case of E9 jointed by N38 nail has 2 out of 10 failed before 1 million cycles indicating that the fatigue limit might be under 60% load level. The average static maxi mum load of not -failed joints after 1 million cycles remain almost the same. The breaking points measured from the nail top are always longer than the width of side member indicating that the loading condition of nail under lateral withdrawal could not be assumed to be a cantilever beam.

並列關鍵字

Box nail ； Lateral resistance ； Fatigue test ； Japanese cedar ； Oriented strand board