地铁工程钢筋混凝土梁疲劳损伤演化和寿命预测模型研究

Investigation on Prediction Models of Damage Evolution and Fatigue Lifetime for Reinforced Concrete Beams of Metros

针对地铁工程钢筋混凝土结构服役期间疲劳现象和腐蚀问题,以应力水平(0.6、0.7、0.8)、杂散电流强度(10、20、30、40 V)和氯离子浓度(2.5%、3.5%、5%、10%)为主要变化参数,使用荷载控制对预腐蚀开裂后钢筋混凝土梁进行了腐蚀-四点弯曲疲劳试验模拟,并获得了杂散电流、氯离子和疲劳荷载作用下试验梁跨中挠度变化规律。试验结果表明:各个试验梁的挠度发展过程大致相似,均大致呈现出三阶段的“S”形特征。基于试验梁跨中挠度演化规律,建立了杂散电流、氯离子和疲劳荷载共同作用下钢筋混凝土试验梁挠度演化半经验解析模型,模型参数与材料属性、腐蚀环境和荷载等试验条件有关,并由试验确定。在此基础上进一步提出了模拟地铁服役环境下钢筋混凝土梁疲劳寿命预测模型和损伤演化模型,从而可以避免进行大量的疲劳试验。借用该模型预测杂散电流、氯离子和疲劳荷载共同作用下试验梁的疲劳寿命,并与试验结果进行对比分析,发现预测值与试验结果吻合良好,进一步证实了方法的可行性和有效性。

In this study,to address the fatigue and corrosion problems of reinforced concrete structures of metros during service life,the cyclic load level(0.6,0.7,and 0.8),stray current intensity(10,20,30,and 40 V)and chloride ion concentration(2.5%,3.5%,5%,and 10%)were used as the main variable parameters to examine the mechanical behaviour of reinforced concrete structures of metros in a four-point bending corrosion-fatigue test under load control.The mid-span deflection variation law of the test beam under various combinations of stray current,chloride ion concentration,and fatigue loading was obtained.The test results show that the progressive processes of deflection of each test beam are similar and feature three stages of an S-shape during the entire test.According to the test results for mid-span translational deflection of the test beam,a semi empirical analytical model for the deflection evolution of reinforced concrete beams under co-action of stray current,chloride ions and fatigue loading was proposed.Furthermore,the undetermined model parameters were related to the material properties and corrosion environment,and load conditions and could be regressed by means of experimental results.Based on this model,the fatigue life and the damage-evolution prediction models of reinforced concrete beams were further developed,and thus,the large number of fatigue tests that would otherwise be required was reduced.The present models were used to predict the service life and damage accumulation of metro reinforced concrete beams in a corrosive environment and under fatigue loading.A comparison of the predicted values with the test results indicates a good agreement between the two,thus verifying the feasibility and effectiveness of the proposed method.