| 摘要 |
PURPOSE:To prevent a crack from occurring at a corner part, by a method wherein crack-preventing structure is provided at the corner parts of a square opening part on a base material and stress concentration is avoided. CONSTITUTION:An opening part 4 on a base material 2 for a wall panel 1 is composed of wooden pieces 5, 6 for reinforcing the peripheral part thereof and corner parts 7 each are formed at the four corners. Cutouts 8 cut out in square shape each are formed at the corner parts 7. The cutout 8 is formed so as to protrude outward from a square angle part 71, and the square angle part 71 is formed in edgeless shape. In this way, the strength of the corner part 7 of the opening part 4 is improved and a crack is prevented from occurring at the corner part 7. |
