Evaluation Of Stirrup Fractures Due To Experimental Simulations Of ASR

In recent years, due to the Alkali-Silica Reaction (ASR) expansion, the bending part of stirrups is frequently fractured. It is reported that due to the expansion, cracks along with deformations are produced in the actual structures. Among them, opening deformation in corner can promote the initial cracks in stirrups progressing, which can lead stirrups to fracture. So far, opening deformations of stirrups, which have been estimated indirectly based on the deformations of external concrete, have not ever been verified directly. So it is important to find the relationship between characteristics of external deformation and stirrup fracture; besides, to investigate the stirrup deformation directly is also significant.In order to simulate the effect from inner ASR expansion on external degradations and fracture of stirrups with restrained concrete, the expansive mortar is cast in the square hollow surrounded by the ordinary concrete as the frame. Experiments using 6 specimens have been carried out. The parameters are stirrup ratio and size of frame concrete for checking the different restrictive conditions; casting area of expansive mortar for studying effects from different expansion amount; further, rebar types for investigating the influence on stirrup damages.During experiments, the surficial cracks and deformation conditions have been measured to presume the inner stirrups movements; besides, the initial cracks in different types of stirrups have been observed, furthermore, the progressing cracks also have been evaluated after inner expansion.Then, give detailed classifications of external degradations and evaluation of stirrup movement. The further study objective is to evaluate characteristics and mechanisms of external deformations and to investigate the movement of stirrup directly. The crack and deformation conditions induced by the inner expansion are studied and classified. Besides, their possible generating mechanisms are discussed. At last, to investigate the stirrup movement induced by the external deformation directly, states of stirrup are recorded and measured before and after the expansion. The angular degree for bending part of stirrup is evaluated. As a result, by using the combination of evaluation for external degradation and stirrup movement, reason for stirrup fracture is estimated.