| In Japan、 many rock-sheds have been constructed over highways along mountains and coastal lines with cliff to protect humans and transportation net works from falling rocks. So far、 these structures have been designed by statically acting maximum impact force evaluated by means of Hertz contact theory and on the basis of the allowable stress design concept. However、 it is well known that these structures have much safety margin with respect the design value of the impact energy. Then、 if it is possible to design those following the performance-based design concept、 downsizing of the cross section of the structures may be achieved and also construction cost can be decreased. From this point of view、 in order to accumulate basic knowledge for establishing performance-based impact resistant design procedure of the reinforced concrete (RC) rockfall protection galleries、 consecutive falling-weight impact test of a 1/2 scale model of the actual galleries covered with a 90 cm depth sand cushion was conducted、 in which a 10 ton weight was used to input the impact energy. In this test、 impact response behavior of the gallery model from elastic to plastic region was investigated by increasing the falling height of the weight from 1 m up to 25 m. From this study、 the following results were obtained: 1) maximum impact force can be better evaluated by means of Hertz contact theory with Lame’s constant of λ = 1、000 kN/m2 and considering an amplification factor due to aspect ratio of the falling weight to the depth of sand cushion; and 2) the roof slab reaches the ultimate state in the flexural failure mode. |
