鋼製透過型砂防堰堤の保有耐力照査に関する一考察

抄録

Recently, many large-scale debris flows have occurred due to the torrential rainfall under climate change, and the steel open dams have been occasionally damaged. To this end, this paper proposes a safety verification method on the load-carrying capacity of steel open dams against the large-scale debris flow (level Ⅱ load). In this method, the maximum load-carrying capacity of a steel open dam should be larger than the required load-carrying capacity of a steel open dam, which means the necessary resistance force of a steel open dam against level Ⅱ load and it is found by using the energy constant law. As the numerical examples, the maximum and required load-carrying capacities of three steel open dams with different structural shapes (i. e., truss type, frame type and mixed type) are investigated by performing an incremental elastic-plastic analysis (pushover analysis). As the computational results, it was turned out that the truss type has the largest strength, while the frame type has the largest ductility and the mixed type has the intermediate behavior. It was verified that all three steel open dams were satisfied with the safety criteria on the load-carrying capacity. It was also inspected if the energy constant law may be applied to the steel open dams under the level Ⅱ load or not, by comparing the response displacement obtained in the energy constant law with the displacement which is found by the pushover analysis at the same energy condition. Finally, the redundancy (reserved strength) of each steel open dam is examined and compared with the required load-carrying capacity of each steel open dam. It was recognized that the redundancy of frame type is the largest, next one is mixed type, and last one is truss type, which are the same tendency as the margin of required load-carrying capacity against the maximum one.