纵筋锈蚀无腹筋混凝土梁抗剪性能细观数值研究

Corrosion effects of longitudinal reinforcement on shear behavior of concrete beams without web reinforcement

以钢筋混凝土梁为研究对象,考虑钢筋非均匀锈蚀膨胀效应,建立三维钢筋混凝土梁剪切破坏分析的数值分析模型.通过多阶段分析方法(钢筋锈蚀阶段,构件性能退化阶段)探索锈蚀对结构力学行为的影响.钢筋的非均匀锈蚀膨胀以施加非均匀径向位移的方式模拟,获得保护层的破坏状态,并以此“最终状态”作为之后混凝土梁静载试验的“初始条件”输入,进而模拟构件的力学行为.在验证了多阶段数值模型合理性的基础上,分析了纵筋锈蚀、剪跨比对无腹筋混凝土梁抗剪性能的影响规律.结果表明,纵筋锈蚀使混凝土梁产生明显的纵向裂缝.纵筋锈蚀率增大,保护层开裂区域增加,梁的抗剪承载力下降严重.另外,剪跨比对梁的抗剪承载力产生影响,剪跨比对未锈蚀梁的影响明显大于对锈蚀梁的影响程度.最后,基于模拟结果对相关设计规范中的抗剪承载力计算公式进行了讨论,发展建立了考虑锈蚀影响的无腹筋混凝土梁抗剪承载力计算方法.

Rebar corrosion is the principal factor affecting the service performance of reinforced concrete(RC)structures.Corrosion reduces the effective area of rebars as well as performance,and weakens the pin bolt effect of rebar on concrete.In addition,when the rebar is severely rusted,the concrete cover breaks,and the bond behavior between reinforcement and concrete deteriorates,affecting the mechanical properties of RC structures.In this study,a three-dimensional numerical model for shear analysis incorporating the nonuniform corrosion of reinforcement was established using an RC beam as the research object.The effects of corrosion on the mechanical behavior of the RC beam were explored via a multistage analysis method(namely,corrosion-induced expansion stage and structural deterioration stage).To model and simulate the expansion of the corrosion products,nonuniform radial displacement was applied to the concrete surrounding the rebar.The cracking process and the damage patterns of concrete resulting from corrosion were obtained.Then,taking the corrosion state as the initial condition,the static load was applied to analyze the mechanical behavior of the RC beam.After verifying the rationality of the multistage numerical model,the effect of the corrosion of tensile reinforcement and the shear-span ratio on the shear behavior of concrete beams without web reinforcement was analyzed.The modeling analysis results show that the corrosion of longitudinal reinforcement causes obvious longitudinal corrosion fractures in the concrete beam.Moreover,with the development of corrosion,the cracking area of the protective layer increases,reducing the shear capacity of the beam significantly.Furthermore,the shear-span ratio has a larger effect on the shear capacity of noncorroded beams than that of corroded beams.Finally,based on the simulation results,the calculation formulas of shear capacity in relevant design codes were discussed,and a methodology for predicting the shear capacity of RC beams without web reinforcement was proposed.