Microcracks in concrete can coalesce into larger cracks that further propagate under repetitive load cycles. Complex process of crack formation and growth are essentially involved in the failure mechanism of concrete. Understanding the crack formation and propagation is one of the core issues in fatigue damage evaluation of concrete materials and components. In this regard, a numerical model was formulated to simulate the thorough failure process, ranging from microcracks growth, crack coalescence, macrocrack formation and propagation, to the final rupture. This model is applied to simulate the fatigue rupture of three-point bending concrete beams at different stress levels. Numerical results are qualitatively consistent with the experimental observations published in literature. Furthermore, in the framework of damage mechanics, one damage variable is defined to reflect stiffness reduction caused by fatigue loading. S-N curve is subsequently computed and the macroscopic damage evolution of concrete beams are achieved. By employing the combined approaches of fracture mechanics and damage mechanics, made possible is the damage evolution of concrete beam as well as the microscopic multiple fatigue crack simulation. The proposed approach has the potential to be applied to the fatigue life assessment of materials and components at various scales in engineering practice.

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The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/adem.202100709.

The mechanical analysis of a novel plywood formwork structure with steel frame was studied with finite element method systematically. By optimizing the parameters of the section shape, node position and the number of formwork heel, a kind of the optimization design scheme was presented. Less building construction materials and better mechanical property was accomplished by the scheme. By contrasting the optimization results with experimental results, the design method is valuable.

Taking a project’s integrated logistics dry port as an example, the advantages and disadvantages of several commonly used refrigerants and their systems are compared and analyzed from safety, environmental protection and energy saving. The technical principles of the NH3 / CO2 refrigerant cooling system are briefly described, and the introduction is also introduced. The refrigeration system selection, equipment configuration and automatic control system scheme of the project refrigerator were provided, which can provide a reference for the selection of the refrigeration scheme of the cold chain project in the future.

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