| 摘要 |
PROBLEM TO BE SOLVED: To provide a precast box culvert which can be immune to a high-level stress in the case of earthquake without making the weight excessive.SOLUTION: As means for reducing the weight of a box, a perforated slab is used for a reinforced-concrete slab constituting the box. Stress degree distribution in accordance with a flexure moment is triangular distribution which becomes maximum (minimum) on a surface of the slab. Therefore, by providing a circular void in the center of slab thickness, the weight of the reinforced-concrete slab can be reduced without impairing a resistance performance of the slab with respect to flexure. In a large-sized box, a degree of flexure stress becomes dominant, and a shear stress degree can be generally charged by a cross section excluding the void part. By making the void cylindrical, the risk of destroying the void part with a local compression force is reduced. Therefore, paper or a thin steel plate is used for a frame forming the void but by using a steel pipe capable of charging stress, a structure is made stronger. In the case of a sectional box, a jig for assembling members using a precast box culvert can be mounted. |
