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The fatigue behavior of RC beams subjected to moving loads is experimentally investigated. Analytical scrutiny is made on the shear fatigue behavior of RC beams subjected to moving loads based on strain path and time dependent fatigue constitutive models rooted in the multi-scale fixed four-way crack modeling of concrete. Moving load is found to cause dramatic reduction in fatigue life of RC beams as compared to that of the fixed pulsating load both in the experiment and analysis. The mechanism for the reduced fatigue life under moving loads in RC beams is discussed in contrast to that of RC slabs. A simplified relation for the prediction of fatigue life under moving load is proposed for practical use on the basis of standard shear fatigue design equation of JSCE code, used for fixed fatigue loading. The effect of randomness in the position of loading is examined and its implication for the reliability of current fatigue life assessment method of RC members is put forward. The applicability of the multi-scale computational platform is verified for the fatigue investigation of RC beams subjected to moving loads.

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This paper investigates the causes of excessive long-term deflection of PC bridge viaducts by using 3D integrated material-structural analyses to take into account the coupled chemo-physics at various scales from the molecular size of water to the structural members. The excessive deflection observed at site is found to be rooted in the deformation of cement paste stemming from both externally applied loads and internal stresses driven by capillary surface tension and disjoining pressures in micro-pores. Not only the former but also the later effect is focused in the serviceability control of PC viaducts. It is found that the nonlinear, long-term deflection of the bridge viaduct can be approximately separated into the components of deflections provoked by external mechanistic and internal thermodynamic actions, even though each component is nonlinearly associated with the thermodynamic states of moisture in micro-pores of cement hydrates.