Multi-scale based Simulation of Shear Critical Reinforced Concrete Beams Subjected to Drying

Abstract

The impact of drying at both material and structural levels is discussed based on the multi-scale thermo-mechanistic modeling. The effects of hygral states at nano to micro scales on the macro scale mechanics are focused on. It is quantitatively confirmed that the moisture state-dependent tensile strength and crack-dependent moisture diffusivity models play a key role in tackling with the responses of reinforced concrete (RC) members subjected to combined hygromechanical actions. Full 3D thermo-mechanics simulation of shear critical RC beams with effective depths, which ranges from 250mm to 1000mm, is carried out from the onset of casting. It is found that the impact of drying increases with the increasing effective depth at the constant beam width. Overall, it is emphasized that linkage of material science and structural mechanics is indispensable for holistic understanding of RC members under coupled mechanical loading and drying. The multi-scale analytical scheme is proved to be applicable for the performance assessment of RC members at ultimate states as well.

Mechanism of Long-Term Excessive Deformation and Delayed Shear Failure of Underground RC Box Culverts

“…This is called as Pickett effect (Pickett 1942;Bazant 2001). This nonlinearity is consistently simulated in considering moisture transport and the constitutive model for cement paste of meso-scale (Asamoto et al 2006) before and after cracking (Maekawa et al 2008;Yoneda et al 2014Yoneda et al , 2015. The coupling of sustained stresses and drying was also found to cause an excessive deflection of long-span PC box sectional viadcuts of about 10 years after construction (Bazant et al 2010;Ohno et al 2012).…”

“…The integrated modelling used in this study has been already verified regarding the reduced shear capacity of drying RC members (Gebreyouhannes et al 2014). Then, this drying effect of structural concrete is implicitly taken into account in the shear failure simulation as shown in Fig.…”

“…The multi-scale integrated analysis (Maekawa et al 2008, Yoneda et al 2014, Gebreyouhannes et al 2014 used in this study brings about the delayed shear failure computationally as shown in Fig. 28.…”

“…At the same time, differential shrinkage of concrete is associated with long-term deformation and shear failure (Yoneda et al 2013), because the inside space of box culverts is rather dry but their outer surface is surrounded by wet soil fundation and/or underground water. Since the out-ofplane shear failure is a problem in danger, the diagonal shear crack propagation, which is possibly associated with drying shrinkage of concrtete, shall be simulated (Gebreyouhannes et al 2014) as well. Furthermore, the nonlinear soil-structure interaction is to be consiered for investigating the mecahnism of damages Moshirabadi et al 2015).…”

“…8. Figure 9 shows the FE discretization and the mix proportion and the material properties were used for input information of the integrated thermodynamics (Maekawa et al 2008, Maekawa andIshida 2002) As the moisture migration is in one-way and wetting/drying is defined on the upper and lower faces of the section, comparatively smaller size of elements is specified and the mean sizes of the elements placed around the core of the section are about twice the average size of coarse aggregates in consideration of moisture migration analysis and local moisture exchange between aggregates and surrounding cement paste phases (Yoneda et al 2014). Here, the cement hydration just after the mixing and associated micro-structure formation was computed in time and space, and the timedependent deformation of cement hydrates were simulated with the moisture states kept in the formed micropores.…”