Concrete has become the most used material on Earth over the 200 years following the invention of modern cement. The design concept has undergone a transition from the allowable-stress design method, limit-state design method, to the performancebased design method, in response to the evolution of materials, sophistication of experimental facilities, and advancement of computation skills. From the issues on resources and energy depletion, global warming, and resilience etc., it is necessary to create a new design framework taking into consideration the required performance beyond the conventional concept, in order to construct infrastructure and buildings in a more rational way.In other words, we should construct a design system that sets the continued existence of the diverse and rich global environment as its most important criterion of value. In this paper, we review the design and technology system developed in the past and discuss it based on the above-mentioned new viewpoint, while constructing and presenting a new design system for concrete structures, focusing mainly on the concept of sustainability, which is regarded as the most important factor in achieving conservation of Earth's rich resources as well as sound socio-economic activities of humankind in the future, and we examine its feasibility.

The authors developed the butterfly web bridge structure, an "innovative" bridge technology, to tackle the issues on lifespan extension, durability enhancement, high seismic resistance by reducing the weight and member size, and shortening of construction term. This bridge structure is characterized by the use of butterfly-shaped prefabricated prestressed high-strength, concrete panels for the webs. The butterfly web bridge seems to have a great advantage. However, the major issue is how to evaluate the advantage afforded by the "innovative" bridge technology that completely differs from conventional techniques. "Sustainability thoughts" is a solid foundation for such evaluation. The purpose of this paper is to quantify the performance of the butterfly web bridge from the standpoint of sustainability that consists of social, economic, and environmental aspects, thereby objectively evaluating the advantage of this "innovative" bridge technology. From the sustainability evaluation, it is concluded that the butterfly web bridge developed to meet a wide variety of complicated requirements is superior than conventional structures from the social, economic, and environmental aspects and also an innovative structure with high sustainability can be created through a comprehensive development approach involving design/execution methods in consideration of all sustainability elements. K E Y W O R D Sbutterfly web bridge, CO 2 , construction term, innovative technology, prestressed concrete, sustainability evaluation

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The World Commission on Environment and Development of the United Nations defined “sustainable development” for the first time in 1987, indicating the necessity for considering development that fulfils the needs of both present and future generations. However, the current situation of the sharp growth in the population and resources/energy consumption that adversely affects the global climate has been adding significance to the concept of sustainable development. From this background, the authors proposed a sustainability design system. This design method includes systems to clearly set the performance requirements to be considered with respect to social, economic, and environmental aspects, calculate the attained performance, and verify if the performance requirements are met. This paper describes the application feasibility of the sustainability design through the above procedures using an existing prestressed concrete viaduct. Additionally, comprehensive evaluation is carried out regarding the relationship between the elements of sustainability in comparison with the general method to clarify the effectiveness of sustainability design. It is concluded that sustainability design system has great potential of its applicability to concrete structures and promoting technical innovation based on setting of high‐performance requirements.