A direct path-integral scheme with fatigue constitutive models for concrete tension, compression and rough crack shear is used to predict the life-cycle of RC slabs. The three-dimensional fatigue analysis successfully predicts the characteristic mode of failure under moving loads as well as in the case of fixed-point pulsation in shear. Importantly, drastically shortened fatigue life under traveling wheel-type loads is mechanically demonstrated by implementing a constitutive model of cracked concrete using a direct path-integral method of fatigue damage simulation. A sensitivity study is carried out to clarify the influence of shear transfer decay and compression fatigue on RC slab performance. The effect of boundary conditions on fatigue life is also investigated.

Three-Dimensional Fatigue Simulation of RC Slabs under Traveling Wheel-Type Loads

Multi-scale simulation of freeze-thaw damage to RC column and its restoring force characteristics

Purpose – The paper aims to propose a rate‐dependent model of structural concrete in combination with the kinematics of condensed water.Design/methodology/approach – First, the paper proposes the coupling model of water versus cracked concrete with a mathematical completeness of equilibrium and deformational compatibility. The proposed model deals with anisotropy of structural performance and of permeability, which is a particular issue of concrete caused by cracks. The governing equation for saturated concrete in this study is based on Biot's theory that deals with particle assembly as a two‐phase composite. Second, the paper shows the possible reduction of the fatigue life of real‐scale bridge RC decks owing to the water residing in structural cracks under moving wheel‐type loading.Findings – The paper shows that the existence of water possibly has an influence on the rate‐dependency of structural performance. The comparison of transition of pore pressure and principal strain indicates that damage to th...

Rate‐dependent model of structural concrete incorporating kinematics of ambient water subjected to high‐cycle loads

This paper aims to upgrade the poro-mechanical scheme to simulate concrete volume change and damages which are strongly coupled with both alkali silica reaction (ASR) and freeze-thaw cycles (FTC). The interaction of two impacts are modeled by considering ASR gel intrusion and ice formation in micro pores and crack gaps, gel movement and unfrozen water suction into entrained air, gel and water migration through cracks as well as equilibrium and mass conservation of both concrete skeleton and mixed pore substances. For the assessment how the proposed numerical scheme works, sequence of events on ASR and FTC is focused on. It shows that ASR can reduce the FTC expansion for nonair-entrained (non-AE) case, but increase the frost damage for air-entrained (AE) concrete. Similarly, the FTC damaged concrete will have a smaller ASR expansion for non-AE case, but a greater expansion when AE admixture agent is dosed. The simulated behaviors also agree well with past experiments of combined ASR and FTC. Finally, the analysis on short-term strength shows that the ASR damaged concrete has a higher residual compressive strength and ductility rather than FTC damaged one due to viscous ASR gel which stand for broken symmetry of damage fields.

https://www.jstage.jst.go.jp/article/jact/15/7/15_346/_pdf

Strong Coupling of Freeze-Thaw Cycles and Alkali Silica Reaction - Multi-scale Poro-mechanical Approach to Concrete Damages -

Simulation of spatially non-uniform frost damage in RC beams under various exposure and confining conditions

Transient nonlinear analysis is proposed as a way of predicting the long-term deformation of cracked reinforced concrete and a mechanistic creep constitutive model for post-cracking tension-stiffness is presented. The effect of drying shrinkage is integrated into the predictive scheme using the thermo-hydro physics of porous media, and a simple equivalent method of analysis is discussed for the practical performance assessment of structural concrete. Careful verification of the model is carried out with respect to the creep deflection of RC beams and slabs subjected to multi-axial flexure. Three-dimensional fiber and plate & shell elements are used for the space discretization of the analysis domain.

Yutaka Itoyama

Papers

Time-Dependent Space-Averaged Constitutive Modeling of Cracked Reinforced Concrete Subjected to Shrinkage and Sustained Loads