Seismic Fragility Analysis of Multistory Masonry Structures Strengthened by Engineered Cementitious Composites (ECCs)

Strengthening multistory masonry structures with engineered cementitious composites (ECCs) overlay is a new strengthening method that can save construction time and achieve minimal disturbance. To investigate the effectiveness of various ECC overlay layout strategies, this manuscript studies the seismic fragility of ECC‐strengthened masonry structures with different strengthening methods. An equivalent framework model based on OpenSees for ECC‐strengthened masonry structures was first established and validated through shake‐table tests. Then, 25 ground motions were selected for incremental dynamic analysis of the ECC‐strengthened masonry structures, and the seismic fragility curves were obtained. Finally, the effects of ECC overlay thickness ( t ECC ), ECC overlay configuration strategy, and ECC overlay length ratio ( R l ) were analyzed. The interstory drift ratio (IDR) was employed to assess the structural performance levels. The numerical results of the equivalent framework model show close agreement with experimental results, demonstrating the validity of the modeling methodology. ECC‐strengthening method can significantly improve the seismic performance of masonry structures, reducing the collapse probability from 30.6% to 2.2 × 10 −5 at Maximum Considered Earthquake. As t ECC increases, the number of strengthening walls increases, and R l increases, the IDRs and the fragility of the structures decrease, with significant impacts. A strengthening scheme with ECC overlay thickness of 20–40 mm, exterior walls strengthening, and ECC overlay length ratio of 1.0 was suggested in practical engineering.