スギ材の密度及びヤング率の違いが木質構造柱脚接合部性能に及ぼす影響

摘要

在来軸組構法の木造住宅において，地震力や風rn圧力などの水平荷重に対する主な耐力要素は，筋rnかいや面材等を施した耐力壁である。そのため，rn木造住宅の耐震性能を向上させるためには，耐力rn壁性能の確保が重要である。一般に，耐力壁に水rn平荷重が作用した際，柱，梁，桁，土台等の接合rn部に応力が集中する。%The objective of this study is to clarify the effects of wood quality on strength performance of column base joint in timbers structure. Density (p) and dynamic Young's modulus (E_(fr)) were measured for kiln-dried sugi (Cryptomeria japonica D. Don) timbers. After measuring the p and E_(fr), they were graded into 3 groups by p (Dl: 0.34 to 0.38 g/cm~3, D2: 0.43 to 0.44 g/cm~3, and D3: 0.48 to 0.54 g/cm~3) and 4 groups by E_(fr) (El: 4.30 to 6.10 GPa, E2: 7.40 to 8.00 GPa, E3: 8.54 to 9.50 GPa, and E4: 9.51 to 11.70 GPa) . Column base joint specimens were prepared by using sugi timbers from each group. Nail joints with steel side plates (V-plate: VP) or fastening attachment (hole down attachment) between columns and sills. Strength performance of column base joint specimen, such as maximum load (P_m), yield resistance (P_y), initial stiffness (K), energy (E), and ultimate resistance (P_u), was evaluated by vertical pull-up test. When the VP was used for joint between column and sill, strength performance, increased with increase in p of sugi timbers, except for K. On the other hand, significant difference in strength performance was not recognized in the specimens used hole down attachment in p graded timbers. In addition, all values obtained in the present study were higher than those for allowable stress design. When the column base joint specimens were prepared by using E_(fr) graded timbers, no significant differences in strength performance of column base joints were found among the E_(fr) graded groups. These results obtained here indicate that strength performance of column base joint is not largely affected by the wood quality of timbers, such as p and E_(fr).