Abstract
Concentrating on the structure with 40% stirrups fractured caused by ASR, the mechanism for stirrup damages is evaluated based on the investigation data that is obtained during the replacement. From observations of the alignment order for damaged stirrups, the distribution trend of damage is analyzed. Moreover, crack depths in 44 stirrups from the same corner section of the structure are observed in detail. Rather than caused by the shape and partial area of structure, it is considered that there are causal factors to induce the different damages in stirrup itself. One influential factor is speculated as the different initial crack depths in stirrups owing to the crush of ribs during the bending operations. Besides, in order to evaluate the effect on stirrups, the distribution and the directionality of cracks are discussed in the cross section cut along the perpendicular to the bridge beam axis. Therefore, from the estimation of deformation behavior in the cross section, the expansion feature influencing the region inner the stirrup is learned. As a consequence, it is considered that the bent part of stirrup has the opening deformation owing to the effect of ASR expansion, which further yields the results that stirrups with initial crack or defect are fractured randomly.
