Semi-Integral Architecture: A Strategic Perspective on Sustainable Maintenance and Repair Innovation in Social Infrastructure

Abstract: In Japan, maintaining and repairing aging infrastructure has become urgent. Beyond substantial costs, the country faces a compound challenge: a shortage of engineers driven by an aging and declining population. This paper advances a strategic perspective, grounded in product architecture, for reconciling technological innovation and sustainability. Although product architecture is commonly classified as modular (high independence) or integral (high interdependence), this dichotomy fits poorly with infrastructure—such as bridges—designed for long-term service under ongoing maintenance and repair. To address this gap, we previously proposed Semi-Integral Architecture, a sustainable design concept that combines the interdependence of integral systems with the independence of modular systems, enabling partial modification and addition of components while maintaining overall system functionality. We also proposed two innovation models that capture technological change in maintenance and repair technologies: the Partial Innovation Model and the Additional Innovation Model. This study integrates these concepts and examines them through analyses of bridge improvement cases on Japan’s urban expressways. The results indicate that the Semi-Integral type serves as the structural basis for both models, confirm that the two models are used in combination, and identify the existence of spatial-constraint-induced radical innovation, whereby stringent spatial constraints trigger radical innovation. The findings further suggest that the Semi-Integral type aligns closely with Open Innovation (OI)–type collaboration and that this process provides an effective foundation for Human-Centered Design (HCD).

Keywords: Infrastructure, Product Architecture, Semi-Integral Architecture, Innovation Model, Circular Economy, Open Innovation, Human-Centered Design

DOI: 10.54941/ahfe1007000

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