Acoustic emission for monitoring the damage progress on concrete-filled stainless-steel tubes (CFSST) under bending test

This study conducted bending tests on both square and circular concrete-filled stainless-steel tubes (CFSSTs) using Acoustic Emission (AE) technique. The research analyzed the mechanical properties, failure modes, and AE characteristics of CFSST under different steel tube thicknesses and concrete strength conditions. Among series and by tracking the AE wave features (rise time, AE counts and energy), three damage stages are depicted: initial cracking onset (Stage Ⅰ), cracks release and steel tube-concrete interfacial debonding on the tensile zone (Stage Ⅱ), and near failure cracks saturation and growth and steel tube-concrete interfacial debonding on the compression zone (Stage Ⅲ). Rise time and RA-average frequency distributions during testing pinpointed the damage onset and modes shift for different types of CFSST. Increasing the thickness of the steel tube effectively delays structural failure, with circular steel tubes demonstrating better suppression of tube buckling and debonding, ultimately exhibiting a predominant mode-I tensile failure mode. This study provides valuable guidance and experience for the effective health monitoring of CFSST structures.