Tomonori SEKI
Influence of Drying Shrinkage on Time-dependent Change of Bending Crack Width in Reinforced Concrete
Takumi SHIMOMURA
¡¡The purpose of this study is to improve precision of predicting the long-term crack width in reinforced concrete. In particular, this study focuses the influence of drying shrinkage on time-dependent change of crack width.
¡¡First of all, drying shrinkage test of uniaxial RC specimens which modeled concrete between cracks carried out to investigate deformation behavior in concrete between cracks by drying shrinkage. As a result, the influence of local deformation near crack edge is offset by restraint of reinforcement, and so averaged surface strain of concrete between cracks equal free shrinkage. Within the limits of these experimental results, surface strain under restraint of reinforcement is adequately calculated from free shrinkage considering uniaxial elastic restraint. In addition, drying shrinkage in actual environmental conditions is smaller than one in a constant temperature and humidity room, because of effect of rain and sunshine.
¡¡The influence of shrinkage of concrete between cracks on time-dependent change of crack width is examined by sustained loading test of RC beams having different magnitude of shrinkage. As a result, in case that shrinkage of concrete is greater, it much affects increasing of crack width. In contrast, increasing strain in reinforcement little affects it. Therefore, the influence of drying shrinkage in crack width estimates due to consider shrinkage of concrete between cracks. Moreover, Stress in tension reinforcement for crack width calculation is necessary to determine by taking tension stiffening effect and initial stress induced by shrinkage before loading into account.
¡¡Consequently, calculation formula is proposed for bending crack width. The proposed calculation formula is based on experimental results that authors carried out. It is verified that the proposed calculation formula for bending crack width in reinforced concrete could successfully estimate the various experimental results done by authors and other researchers
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