Yuya Takahashi

Development of 3.95 MeV X-band linac-driven x-ray combined neutron source

The existing non-destructive inspection method employed for concrete structures uses high energy X-rays to detect internal flaws in concrete structures and iron reinforcing rods. In addition to this conventional method, the authors are developing an innovative inspection system that uses a mobile compact linac-driven neutron source that utilizes neutron backscattering, to measure the moisture distribution in concrete structures and estimate the corrosion probability distribution of iron reinforcing rods.

Crack-gel interaction on the static and fatigue failure of ASR-damaged RC slabs

The research target of this study is degradation of punching shear strength due to Alkali Silica Reaction (ASR) in Reinforced Concrete (RC) slab members. At first, punching shear strength of ASR slabs was examined experimentally. The deformations of slab specimens due to ASR strongly depended on bar arrangements. Static punching shear strength also depended on bar arrangements. In addition to the static experiments, the fixed-point cyclic loadings were carried out in both dry and wet conditions. The punching shear fatigue strength of ASR-damaged specimen was reduced according to the degradation of the static punching shear capacity, but the further strength reduction was not observed even in case of the wet condition unlike normal reinforced concrete slabs. As the next step, the authors conducted the multi-scale chemo-hygral simulation with ASR-gel generations and migrations. The poromechanics-based multi-phase modeling succeeded to simulate the structural performance of ASR-damaged slabs.

Computational Fatigue Life Assessment of Corroded Reinforced Concrete Beams

Remaining performance of corroded reinforced concrete beams is numerically evaluated by means of poro-mechanics approach. Corrosion substance is treated as the combined phases of liquid and solid gels. The static loading experiment of corroded reinforced concrete beams is fairly simulated by the multi-directional fixed crack model combined with corrosion gel migration. Further, fatigue life of corroded reinforced concrete beams is studied numerically. Even if static shear strength is not reduced so much, remaining fatigue life could be shortened significantly due to the cyclic degradation of cracked cover concrete around expanded steel bars.