基于分形理论的CFRP布增强混凝土梁抗弯性能研究

STUDY ON THE FLEXURAL BEHAVIOR OF THE CFRP-REINFORCED CONCRETE BEAM WITH FRACTAL THEORY

在实验室模拟酸雨腐蚀环境,完成了普通混凝土梁与CFRP布增强混凝土梁的抗弯试验,得到了各级荷载作用下构件表面裂缝的分布与演化过程,验证了受腐蚀CFRP布增强混凝土梁表面裂缝分布的分形特征。基于分形理论分析了受腐蚀混凝土梁在弯曲荷载作用下的开裂及破坏过程,详细讨论了梁表面裂缝的分形维数与其抗弯性能参数(损伤深度、混凝土强度、一阶频率、极限承载力、跨中挠度、位移延性系数)之间的关系。研究表明裂缝分形维数随着损伤深度的增加而减小,CFRP布增强混凝土梁的分形维数大于普通混凝土梁,其分形维数变化率与构件承载力变化率之间存在线性关系;因此梁表面裂缝分布的分形特征可作为CFRP布增强混凝土受弯构件损伤程度的衡量指标的观点,可为今后对"在役混凝土结构承载力和寿命预测的研究"提供参考。

In this study, various artificial acid rain environments were simulated in the laboratory. The reinforced concrete beams and CFRP-reinforced concrete beams were tested after being exposed to artificial acid environments for certain periods. Three-point bending tests were performed to investigate surface crack initiation/propagation of concrete beams. The results indicate that fractal theory can be used to describe the crack of CFRP-reinforced concrete beams. Relationship between fractal dimension and mechanics performance parameters of concrete beams(i.e., damage depth, concrete strength, frequency, ultimate carrying capacity, ultimate deflection, displacement ductility factor) was discussed. It is illustrated that crack fractal dimension decreased with the increase of damage depth. It is found that fractal dimension of CFRP-reinforced concrete beams was larger than that of reinforced concrete beams exposed to the same acid environment. The linear relationship was found between fractal dimension and ultimate carrying capacity of CFRP-reinforced concrete beams. Therefore, the fractal dimension of surface crack could be used to estimate the damage degree of CFRP-reinforced concrete flexural member. These results can provide an effective reference for the evaluation of carrying capacity and service life of the in-service concrete structures.