CLT 床版を対象とした高剛性ビス接合部の開発
CLT床版相互のせん断接合において，従来利用されている平面的斜めビス接合は，接合面に直交する仮想平面に収まる形で，ビスを斜め打ちする方法であり，せん断力をビスの断面で受け，曲げ降伏によって耐力が決まる。そのため高い剛性・耐力を得ることが難しく，必要なビス本数が増えてしまうという課題があった。そこで，本研究ではこのような抵抗機構の改良を目的とし，接合面に直交する仮想平面に対しても角度をつけてビスを打ち込む，立体的斜めビス接合を開発した。この接合について，せん断実験およびFEM解析を行い，ビスの軸方向力としてせん断力を負担できるため，初期剛性が平面的斜めビス接合の約10倍となることを確認した。また，ビス打ち込み時に2方向に角度をつける必要があり，その施工精度の確保が課題となる。そこで，事前加工を考案し，打ち込み角度誤差を±5°の範囲に収めることが可能となった。
キーワード：CLT，床版，せん断，斜めビス，角度精度，FEM解析
＊１ 技術センター 都市基盤技術研究部 木・鋼研究室
＊２ 設計本部
＊３ 設計本部 構造設計第三部
Development of High Performance Screw Joints for CLT Deck Panels
In the shear connection of CLT deck panels, in-plane inclined screws are used conventionally to connect CLT panels so that the screws are driven into the CLT panels so they are positioned within an imaginary plane perpendicular to the joint surface. Bending capacity in such cases is determined by flexural yield because shear force is resisted by the cross sections of the screws. It is therefore difficult to obtain high stiffness and bearing capacity, inevitably necessitating the use of a relatively large number of screws. In this study, we developed a three-dimensional (out-of-plane) inclined screw fastening method, in which screws are driven at an angle to an imaginary plane perpendicular to the joint surface to improve the resistance mechanism. Shear experiments and FEM analyses performed on this connection confirmed that an initial stiffness about 10 times that of in-plane inclined screw joints can be achieved because the shear force can be resisted as an axial force acting on the screws. Since there is a need to inclined screws in two directions, it is necessary to ensure a certain level of construction accuracy. To solve this problem, we devised a pre-processing method so that driving angle error can be kept within ±5%
Keywords: CLT, deck panel, shear, inclined screw, angular accuracy, FEM analysis
*1 Wood/Steel Structure Research Section, Urban Engineering Research Department, Taisei Advanced Center of Technology
*2 Design Division
*3 Structural Engineering Department III, Design Division