海工结构服役寿命预测细观数值模拟研究

Meso numerical Simulation of Service Life Prediction for Marine Structures

关键词:  服役寿命  氯离子扩散  数值模拟  钢筋锈蚀

Key words:  service life  chloride diffusion  numerical simulation  steel corrosion

摘要:

在现有二维混凝土随机骨料模型基础上，通过引入正态分布随机数来模拟混凝土界面过渡区厚度的非均匀性，并耦合氯离子扩散、钢筋锈蚀和混凝土损伤，建立了海工结构服役寿命预测细观数值模型.研究表明：由氯离子扩散引起的单根钢筋非均匀锈蚀导致混凝土保护层形成3条主裂缝，3条主裂缝之间夹角约为120°，出现这种现象的主要原因是界面过渡区加速了氯离子扩散，次要原因是界面过渡区的力学性能劣化；在相同钢筋锈蚀量条件下，非均匀锈蚀钢筋混凝土比均匀锈蚀钢筋混凝土的服役年限短，混凝土保护层开裂形态也不一样；数值模拟的氯离子含量分布、裂缝形态与试验数据较为吻合，验证了所建立的数值模型的可靠性.

Abstract:

Concrete is an anisotropic material composed of aggregate, mortar, and interface transition zone(ITZ). Assuming that the interface transition zone thickness follows a normal distribution, a two dimensional concrete random aggregate model is developed. On this basis, a mesoscopic numerical model for predicting the service life of marine structure is established by coupling chloride ion diffusion, steel corrosion and concrete damage. The numerical simulation of chloride ion content distribution and crack morphology are in good agreement with experimental data, and verifies the reliability of the numerical model. Numerical studies show that chloride ions cause non uniform corrosion of single steel bar, resulting in three main cracks in the protective layer. The angle between the three main cracks is about 120°. The thickness of the interface transition zone has a critical impact on the service life of the marine structures. The main factor leading to this phenomenon is that the interface transition zone accelerates the diffusion of chloride ions, and the secondary factor is the deterioration of the mechanical properties of the interface transition zone. Under the condition of the same amount of steel bar corrosion, the service life of reinforced concrete with non uniform corrosion is shorter than that with uniform corrosion, and the cracking pattern of the protective layer is also different.