This paper presents a multi-scale and multi-chemo–physics platform to evaluate the lifecycle of structural concrete under environmental and mechanical impacts. Following the scheme from nanometer scale of cement hydrated with water molecule to meter scale of reinforced concrete (RC) members, the platform covers characteristic upscaling based on causality and behavioral response toward both environmental and mechanical impacts. During the process, multi-chemo–physics is incorporated to tackle the local equilibrium and global movement, where the associating impact is also considered with mesoscale cracks. With this platform, long-term structural performances are captured while the coupled durability issue is also investigated.

To perform the assessment of reinforced concrete infrastructures in service, a multi-scale simulation has been developed and improved with an integrated hygro-thermal-chemo-electrical-mechanistic approach. Various durability issues are successfully evaluated in terms of fatigue behaviours with damage induced by moisture motion through pores and cracks, temperature-related deterioration such as frost/fire damage, degradation by chemical reaction like alkali-silica reaction, and the macro-cell corrosion coupled with multi-ion equilibrium which is electro-chemical phenomenon. Moreover, the long-term performance evaluation influenced by the drying shrinkage is also successfully conducted. Furthermore, the multi-scale integrated approach is coupled with AI technique and data assimilation techniques. The crack locations and their widths are converted to space-averaged strains, which are built inside the cyber storage for the futural performance prediction. The hazard map of crack patterns on the surface of concrete deck is inversely derived from the artificial neural network, which is built according to the big dataset of the past maintenance records. Through both methods, the importance of using both-eye diagnosis is realized and proposed for lifetime assessment of structural concrete.

Structural reinforced concrete (RC) experiences cyclic loads during their service life, and in practice, the load amplitude can always change, which will lead to a mixed high and low‐cycle fatigue failure. This paper aims to investigate the fatigue behaviors of RC beams under different load levels and more importantly, their sequential effects. Based on the path‐dependent constitutive models, the structural degradation under different repeated loads are comprehensively investigated by numerical simulation of higher consistency with the reality. It is fairly indicated that a clear bi‐linear character may exist in the so‐called S‐N diagram, of which the high‐cycle fatigue failure is attributed to rupture of main reinforcement under tension, while the low‐cycle fatigue failure is controlled by the concrete failure in flexural compression zone. A simple design method to consider mixed low and high cycle fatigue is proposed to quantify this bi‐linear character. For the varying amplitude of cyclic loads, the high‐to‐low loading sequence may cause a shortened fatigue life. More interestingly, if a rather high heavy load (0.85 or 0.95 of the static capacity) is applied just once before ordinary fatigue loads (ex. 0.6), the deflection may significantly increase, while the stiffness and final fatigue life would be slightly reduced in view of nonlinear mechanics.