SHEAR LOAD CARRYING MECHANISMS OF RC BEAMS WITHOUT STIRRUPS STRENGTHENED BY MULTIPLE HOLES

Abstract

 The static loading experiments and three-dimensional finite element (FE) analyses were conducted to make clear the effects of multiple holes which were introduced to recover structural performances of deteriorated reinforced concrete (RC) members in the shear load carrying mechanisms. The experiments and FE analyses were conducted by using the specimen and analytical model of sound RC beams without stirrups. The multiple holes were introduced in the beams by embedding polyvinyl chloride pipes at the time of specimen casting. As a result of experiment, increase in the loading capacities of the RC beams with multiple holes arrayed along a spline curve compared with the control beam was confirmed. To make clear the reasons, analyses based on theoretical decomposition method of arch mechanism and beam mechanism were applied to the experimental results. The results indicated that the loading capacities of the beams with the multiple holes increased by the predominance of arch mechanism with increase in the strength of beam mechanisms. As a result of FE analysis, it was made clear that predominance of the arch mechanism in case of beams with multiple holes arrayed along a spline curve was caused by expansion of the minimum principal stress distributing region. The results also indicated that the expansion was caused by the single hole which located at the boundary of the vertical stress contributed region, and that the crack inducing path coincided with the most effective crack path for the predominance of the arch mechanism due to the single hole.