锈蚀和疲劳耦合下RC梁损伤演变分析和承载力评定

Damage Evolution Analysis and Bearing Capacity Evaluation of RC Beams Under the Coupling of Corrosion and Fatigue

为了对钢筋混凝土(RC)梁的承载力进行准确快速评估,考虑锈蚀和疲劳耦合作用,对RC梁的静刚度进行了敏感性分析,给出了静刚度简化计算方法。以一钢筋混凝土简支T梁为例,计算了锈蚀和疲劳耦合作用下其承载力和刚度的退化情况,对比了不同刚度计算方法的差异,研究了钢筋面积对开裂截面刚度的影响,明晰了刚度与承载力的内在关联,根据承载力损失系数与刚度损失系数之间的关系,给出了基于频率的承载力计算公式。研究结果表明:锈蚀和疲劳耦合作用会加速桥梁承载力和刚度的退化过程;锈蚀对承载力和刚度影响主要体现在钢筋面积减小方面,锈蚀导致的钢筋与混凝土间粘结性能的降低对刚度影响不大;传统刚度计算公式中参数取值不易确定,会影响计算精度。本研究提出的刚度简化计算公式参数少、取值方便、计算结果较准确;对于开裂钢筋混凝土梁,承载力与刚度之间可以通过受拉钢筋面积相关联;承载力损失系数与动刚度损失系数有良好的相关性,可以采用文中给出的基于频率的承载力计算公式对薄弱截面位于跨中附近的开裂RC梁进行承载力评估。

In order to accurately and quickly evaluate the bearing capacity of reinforced concrete(RC) beams, considering the coupling effect of corrosion and fatigue, the sensitivity analysis of the static stiffness of RC beams was carried out, and the simplified calculation method of static stiffness was given. Taking a reinforced concrete simple supported T beam as an example, the degradation of bearing capacity and stiffness under the interaction of corrosion and fatigue was analyzed, and the difference of the stiffness calculation method was compared. The influence of the area of rebar on the stiffness of the cracking section was studied, and the internal relation between the stiffness and the bearing capacity was clarified. According to the relationship between the load loss coefficient and the stiffness loss coefficient, the calculation formula of the bearing capacity based on the frequency was given. The results show that the coupling effect of corrosion and fatigue will accelerate the degradation process of the bearing capacity and stiffness of the bridge, and the effect of corrosion on the bearing capacity and stiffness is mainly reflected in the reduction of the area of steel bars, the reduction of bond properties between steel bar and concrete caused by corrosion is less influenced by the stiffness. The parameter values of the traditional stiffness calculation formula are not easy to be determined. The simplified calculation method of stiffness calculation method proposed in this study is convenient to obtain the accurate results. For cracked reinforced concrete beams, the bearing capacity and stiffness can be related to the area of the tensile reinforcement, and the loss coefficient of bearing capacity is well correlated with the dynamic stiffness loss coefficient. The bearing capacity formula based on frequency can be used to evaluate the bearing capacity of the cracked RC beam when the weak cross section is located near the middle of span.