FRP拉索静力及蠕变性能的多尺度预测

合理而高效的纤维增强复合材料(FRP)拉索性能预测方法可有效解决拉索足尺试验难度大、耗时长等问题。为此,以剪切滞后模型的理念为基础,提出以浸胶纱为基本单元的FRP浸胶纱-单筋-拉索多尺度短期静力与长期蠕变预测模型。相比将纤维单丝作为基本单元的一般模型,该模型具有较高的计算效率,尤其适用于大尺寸FRP拉索的足尺建模分析。以37根4 mm直径单筋的玄武岩纤维增强复合材料(BFRP)拉索作为算例,详细阐述了该模型的建立方法和求解流程,并对静力和蠕变模拟结果进行了分析。其中,模型着重考虑了浸胶纱单元拉伸强度和树脂单元剪切强度的双参数威布尔随机分布、树脂屈服后的界面残余剪应力、浸胶纱单元蠕变断裂寿命模型和树脂基体的长期松弛效应。结果表明:BFRP单筋和拉索静力极限承载力的预测值与试验结果误差均在4%以内,而采用单元平均强度直接换算得到的结果较单筋和拉索预测值分别偏高18.3%和11.3%。在此基础上,模型进一步揭示了由FRP浸胶纱、单筋到拉索的多尺度强度退化规律和拉索内部的短长期损伤演化机理,可为后续拉索性能优化和设计提供支撑。在高应力水平下,较弱单元的提前破坏将直接导致拉索整体过早的失效,进而显著削减整体蠕变寿命;而在低应力水平下,拉索整体的蠕变断裂寿命趋近于浸胶纱单元自身的蠕变寿命。

Static and Creep Simulation of Fiber Reinforced Polymer (FRP) Cable: A Multiscale Study

A full-scale test of large-tonnage FRP cable is a challengeable and time-consuming issue. Thus, an effective predicting model for FRP cable can be very helpful. In this study, based on the shear-lag concept, we proposed a multiscale model from impregnated fiber bundle (IFB), single tendon to entire cable scale. Compared to traditional models made of filament elements, this model has high computing efficacy and is suitable for full-scale modeling of FRP cable. A model of 37-tendon FRP cable is then established with a tendon diameter of 4 mm. The modeling methodology and solving method are demonstrated. The simulated static and creep results are then discussed. In this model, four aspects are carefully considered, including statistical Weibull distribution of element strengths, residual interfacial shear stress, creep lifetime model of IFB elements, and shear relaxation of resin matrix. The predicted results of tensile strength were in well agreement with experimental ones with relative error lower than 4%. If only considered average strength of elements, however, the ultimate capacities of tendon and cable were overestimated by 18.3% and 11.3%, respectively. Then, the multiscale strength pattern of FRP cable were revealed, as well as short- and long- term failure mechanisms. Under high level of creep stress, the premature rupture of weak elements can significantly accelerate the overall failure and reduce the creep lifetime. With low stress level, on the other hand, the overall creep lifetime of FRP cable tended to be identical to that of IFB elements.