an efficient numerical method to define failure surface for concrete structural members repaired by steel jacket

In seismic retrofitting of existing old buildings or reforming theearthquake harmed building sometimes it becomes necessary to improve the seismic performance of concrete sections against future earthquakes byapplying steel cover Thus, prediction the factual behavior of steel covered concretes against lateral loadsis important and needs implementation of nonlinear analysis and considering materials nonlinear behavior To perform nonlinear analysis having access to details of section’s failure surface is essential. The failure surface of a cross section can be defined as the locus of points that correspond to ultimate strength. In this article a quick and efficient numerical method based on fibre method concepts is presented to determine failure surfaces for steel covered concretes Moment-curvature diagrams, bending moment axial force interaction curves and biaxial bending axial force failure surfaces are defined by method. The predicted results show high correlation with experimental results.