いま、性能設計を考える: 国際化と災害激化を受けて

摘要

In Japan, a country frequently affected by earthquakes, the anti-seismic criteria have been repeatedly revised since the time it was first introduced by earthquake legislation after the Great Kanto earthquake occurred in 1923. In addition to earthquakes, other natural disasters including inundation damage due to storm surge in coastal areas, flood damage of rivers, roads and railways caused by heavy rains, and sediment damage have also frequently occurred in Japan. In such a harsh environment, in order to reasonably construct and maintain safe and secure infrastructure, starting with the transition of design method from conventional Specification Based Design to Performance Based Design ("PBD"), a variety of technical standards and categories of standards have been developed specifically, based on types of facilities like rivers, roads, railways, ports, and power transmission, or types of materials like soil, steet-concrete, while various research and development have been carried out and advanced technologies have been introduced. On the other hand, the transition to "PBD" has been accelerated since it is required by the WTO/TBT Agreement ratified in 1995 that international standards should be used as the basis of domestic standards. In order to comply with international standards, comprehensive design codes have been formulated based on the concept of "PBD" in Japan, and revisions of various domestic standards under these comprehensive design codes have been carried out. In this special issue, Performance Based Design is highlighted in order to clarify what is "PBD" which is the basic concept of comprehensive design codes, and what is expected by introducing "PBD".%地震国である日本では、1923年の関東大震災を受け初めて震度法による耐震基準が導入されて以来、繰返し基準の改定が行われてきた。そして1995年の兵庫県南部地震を契機とした見直し、さらに2011年3月11日の大地震を受けてさまざまな基準類のさらなる検討が進んでいる。また地震災害にとどまらず、近年では特に地球温暖化の影響を受け、沿岸域の高潮被害や、豪雨による河川、道路、鉄道等の浸水被害や土砂災害などの自然災害も頻発している。さらには、経年劣化による鋼·コンクリート構造物の維持管理も重要な課題になつている。 このようなわが国独自の厳しい環境の中で、安全·安心な社会資本を合理的に建設·維持していくことを目指して、従来の：仕樣規定型設計法から性能規定型設計法(いわゆる「性能設計」)への行が進んでいる。