A Simplified Two-Step Approach for the Seismic Retrofitting Design of Existing Structures Towards a Resiliency Enhancement

Abstract

The resilience of a community to come across the natural hazard events is gaining popularity in planning and decision-making strategies. To utmost importance in seismic zones, is the safety and operability of structurally vulnerable existing structures, representing a high portion of the built stock. Manifested low resilience has shown many flaws in planning, managing, retrofitting the damaged structures, which in many cases takes years being completed. The scope of the research is to exploit numerical simulation strategies towards a resiliency enhancement by means of optimized retrofitting solutions. At present, the seismic design is based on elastic analysis. A simplified two-step procedure for the seismic retrofitting design is here proposed, by utilizing the capabilities of FE codes to perform advanced nonlinear analyses. In the first step, it is estimated the structural performance of the structure, whilst the vulnerable elements to be strengthened are indicated. A Retrofitting strategy is selected and implemented into the model, and in the second step, the structure is reanalyzed with the same strategy. Based on the obtained responses, each strengthening element is designed adequately to the required limit state. This strategy is computationally burdening; however, the progress in the numerical analyses makes possible its implementation, and the achieved accuracy is nonpareil. The proposed method is illustrated with a masonry church, severely damaged by the Emilia Romagna (Italy) Earthquake in 2012. The retrofitting strategies adopted for strengthening options, are the surface mounted: (a) FRP sheets; (b) GFRP bars and TRCM. Throughout the investigated case study, it is demonstrated that the vulnerable structures exhibit very low resilient features and the best strategy to enhance their resilience is by means of anterior measures.