| 摘要 |
PURPOSE:To increase usability and safety on works, by forming lasting steel stairs in the basement as a hanging structure from a prior working floor and moving down the stairs gradually in accordance with the advancement of excavation. CONSTITUTION:An opening 2 for a lasting steel stairs is opened in the floor plate 1 on the first floor on the ground and a bracket is temporarily installed on the upper edge of the opening 2. And the primary excavation is carried out on the first basement and leveling concrete is placed on the excavated bottom. Next, the first stratum 3a of the lasting steel stairs 3 is hung up by a lifter 5 and inserted in the opening 2 and the upper part of steel posts 31 is fixed to the bracket and hung down. And the underground frame construction works like the floor 7, posts, external walls, etc., of stairs 3 are carried out. And further, the same processes are repeated by turns to connect the second and third strata 3b, 3c to each other so as to construct the stairs 3. |
