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Moisture and cracks are the two scourges of structural concrete, and understanding the multi-scale interactions between the two is the key to determine long-term durability performances. This paper firstly deals with moisture migration/balance and its volume change with creep in in-service PC bridge viaducts that are experiencing excessive deflections by using a-3D integrated micro-material-structural modeling. It is found that moisture-migration related deflections driven by the capillary surface tension and disjoining pressures in micro pores account for 25 to 45% of the macroscopic deflections. This apparent kinematics can be approximated by adding the moisture-related time-dependent deflections to the mechanistic-induced creep by external loads. This paper then deals with shear capacity and post-peak ductility change caused by concrete self-desiccation with autogenous shrinkage, and water-crack interaction in cracked RC bridge decks under moving loads. It is found that the water presence on the upper deck parts, when subjected to high-speed traffics, can shorten the deck fatigue life by one-and-a-half order of life-span. This reduction in life is due to high water pressure developing over a large numbers of wheel passages as well as the reduced shear transfer along crack planes.