Thermo-Mechanistic Multi-Scale Modeling of Structural Concrete at High Temperature

Accelerated Moisture Transport through Local Weakness of High-Strength Concrete Exposed to High Temperature

“…These values are formulated with respect to the specific surface area, which empirically derives from the hydration degree of cement computed by the multi-mineral heat generation model (Ishida and Maekawa 1999;Maekawa et al , 2008. In the upgraded model of high temperature (Iwama et al 2018(Iwama et al , 2019(Iwama et al , 2020b, the increased porosity that results from the released crystallized water is thought to be linked with the dehydration process of CSH solids. Consequently, the varying total porosity in concrete is expressed with the same statistical form as Eq.…”

“…It is assumed that the moisture transport in the local weakness is much faster than that in high-strength concrete. In this study, the liquid and vapor conductivity at the local weakness are simply expressed in the trial analysis as, , 1, 000 On the upgraded scheme (Iwama et al 2018(Iwama et al , 2019(Iwama et al , 2020b, the liquid and vapor conductivities calculated in the multi-scale platform (Ishida and Maekawa 1999;Maekawa et al , 2008 are utilized at high temperatures heating. The thermodynamic phase equilibrium of the idealized vapor gas (Ishida and Maekawa 1999;Maekawa et al , 2008 is expressed as,…”

“…Moreover, in this model (Ishida and Maekawa 1999;Maekawa et al , 2008, the vapor pressure drops when crack or large volume expansion happens. When the pressure drop is great after crack occurrence, one can judge that the cracked concrete piece may leave the structural concrete by explosive spalling (Iwama et al 2018(Iwama et al , 2019(Iwama et al , 2020b. Afterwards, the inside concrete volume is computationally exposed to the ambient states by progressively shifting the boundary condition (Iwama et al 2018(Iwama et al , 2019(Iwama et al , 2020b).…”

“…Thus, the discussion shall be carried forward to structural concrete under external loads. The authors selected the fire resistance of a long RC column with artificially arranged water pipes as the target for validating the multi-scale simulation system (Ishida and Maekawa 1999;Maekawa et al , 2008Iwama et al 2020b).…”

“…The multi-phase hygral simulation (Iwama et al 2019(Iwama et al , 2020b) takes into consideration the decrease in yield strength of reinforcing bars (CEC 1990;JSCE 2004;AIJ 2009) and the varying coefficient of thermal expansion (CEC 1990;JSCE 2004;AIJ 2009). Figure 8 shows the column deformation of the experiment and analysis (Iwama et al 2020b). Case II is the simulation with two water pipes with diameter of 1 mm that cross at the center of the column height.…”