Residual design life-based evaluation of structural retrofitting on high-rise reinforced concrete buildings

The deteriorating structural performance of aging high-rise reinforced concrete (RC) buildings has brought increasing attention to the necessity of retrofitting in developed regions. In this context, the present paper introduces a novel approach by reversing the conventional service life-based structural design procedure. The proposed approach establishes a residual design life evaluation framework, enabling a comprehensive assessment of the performances of existing RC buildings both before and after retrofitting. This assessment framework takes into account various load scenarios, including wind and earthquake forces, etc., and yields an intuitive index based on design codes, termed "residual design life", which serves as valuable information for decision-makers. To exemplify the framework's application, a case study involving a high-rise RC building is presented. Initially, the influence of the adopted design codes on the residual life of the aging building is investigated. Subsequently, three commonly employed structural-level retrofit methods, namely steel bracing, RC wall addition, and exoskeleton, are examined. The findings reveal that the residual design life of the existing building decreases as the adopted design code transitions from an outdated version to the current one. However, the implementation of structural-level retrofit interventions proves highly effective in enhancing the building's residual life, particularly when failure is primarily governed by column capacities and storey drift. Nonetheless, it should be noted that certain structural-level interventions may increase the load on adjacent beams, potentially leading to a negative impact on the building's residual life when the condition of the beams becomes the predominant factor. Furthermore, the obtained residual life of the retrofitted building could be used to assist in conducting life-cycle analysis and further investigations and contribute to the understanding regarding structural performance and safety in the built environment.