Analytical model for local bulging failure of mini-BRBs with circular restraint tubes

Abstract This paper proposes an analytical model for predicting local bulging failure of mini-BRBs with circular restraining tubes. The mini-BRB consists of a quasi-triangular core bar and an external circular restraining tube, and bulging of the tube can occur due to thrust of the inner core bar buckling in high-order mode. To analyze the mechanism of bulging, 4 specimens were designed with restraining tubes of different thicknesses, and strain gauges were attached to external surfaces of tubes to record strain distribution and development during the bulging process. An analytical model was established to obtain the lateral thrust versus bulging depth relationship, and a criterion was proposed to define the bulging resistance of circular tube. Numerical analysis was conducted and the results of which were employed to modify theoretical bulging resistance. Finally, based on experiment results, a performance-based design criterion with a safety factor considering the estimated maximum lateral thrust and the bulging resistance of tube was proposed to prevent premature local bulging failure.