Experimental and analytical study of retrofitting encased composite columns with different techniques

Encased composite columns (ECCs) may need retrofitting because of increased loading demands, changes to design standards, and design deficiencies during their service life. This adaptation is cost-effective and sustainable, eliminating the need for complete demolition and reconstruction, making it a viable solution. This study examines external retrofitting techniques for improving the performance of ECC columns. The techniques include corrugated sheets, flat steel sheets, spiral steel sheets, spiral steel stirrups, steel welded wire mesh, steel angles, and steel straps. Eight encased composite columns were fabricated and tested concentrically. The results were confirmed via nonlinear finite element analysis (ABAQUS 20). The best, simplest, and least expensive technique for retrofitting was the use of four steel angels and spiral steel stirrups 8 mm in diameter, which resulted in an increase in the load capacity of 56.9%. The results revealed that corrugated sheets increased the control ultimate load capacity by.60% and 58%, whereas steel welded wire mesh increased the load-carrying capacity by 47%. The use of spiral flat steel sheets and flat steel sheets resulted in increases of 48% and 44% in the control ultimate capacity, respectively. A comparison of the experimental and finite element analysis results revealed satisfactory agreement, allowing further theoretical studies using ABAQUS software. These results will extend parametric studies by using finite elements to conduct more studies on retrofitting composite columns.