Probabilistic Durability Assessment of Concrete Structures in Marine Environments:Reliability and Sensitivity Analysis

A probabilistic framework for durability assessment of concrete structures in marine environments was proposed in terms of reliability and sensitivity analysis, which takes into account the uncertainties under the environmental,material, structural and executional conditions. A time-dependent probabilistic model of chloride ingress was established first to consider the variations in various governing parameters, such as the chloride concentration,chloride diffusion coefficient, and age factor. Then the Nataf transformation was adopted to transform the nonnormal random variables from the original physical space into the independent standard Normal space. After that the durability limit state function and its gradient vector with respect to the original physical parameters were derived analytically, based on which the first-order reliability method was adopted to analyze the time-dependent reliability and parametric sensitivity of concrete structures in marine environments. The accuracy of the proposed method was verified by comparing with the second-order reliability method and the Monte Carlo simulation. Finally, the influences of environmental conditions, material properties, structural parameters and execution conditions on the time-dependent reliability of concrete structures in marine environments were also investigated. The proposed probabilistic framework can be implemented in the decision-making algorithm for the maintenance and repair of deteriorating concrete structures in marine environments.

Effect of Hydrophobic Modification on the Durability and Environmental Properties of Porous MgF_2 Antireflective Films

Conventional porous MgF2 antireflective films show poor environmental durability due to its hydrophilic nature.To improve the film environmental durability,hydrophobic porous MgF2 antireflective films are prepared by a methyl silicone-modified MgF2 sol.Effects of the methyl silicone proportions on the film properties are examined in order to control the wettability,peak transmittance,and environmental durability of the films.The modification of methyl silicone can increase the film hydrophobicity,thus decreases the adsorption of water,and improves the environmental durability.However,large amounts of methyl silicone could increase the film refractive index,resulting in the decrease in peak transmittance for films on BK7 glass.Films with 40% silicone show water contact angle of 110°,peak transmittance of 98.7%,and good environmental durability.The results of accelerated test show that the environmental durability of the porous MgF2 films modified with 40% methyl silicone is six times higher than that of the conventional films.

Full‑Color Tunable and Highly Fire‑Retardant Colored Carbon Fibers

Carbon fibers(CFs)are widely used in various cutting-edge fields,such as aerospace,military,automobiles,and sports,owing to their unique combination of excellent mechanical properties,good thermal stability,and lightweight.However,their inherent super-black appearance makes it difficult to satisfy the aesthetic/fashion requirements of the colorful world,and the flammability of CFs severely limits their practical utilization in high-temperature and other extreme environments.Herein,we fabricated full-color tunable colored CFs on a large-scale via atomic layer deposition,based on the monolayer film interference strategy.CFs exhibited brilliant colors and excellent environmental durability in extreme environments,such as intense ultraviolet(UV)irradiation,accelerated laundering,friction,high-temperature,and low-temperature treatments.Colored CFs also exhibited excellent fire-retardant performance that could withstand alcohol-lamp flame burning for 60 min.Our work provides insights into an innovative material/structural design that can help achieve rapid development of the CF industry and global carbon neutrality/sustainability.