ECC-混凝土叠合梁弯曲试验及裂缝发展的分形表征  

Fractal Characterization of Flexural Performance and Crack Propagation of ECC-Concrete Composite Girder

作　　者：赵卫平[1] 王磊 项荣军 李昕鑫 刘英健 ZHAO Weiping;WANG Lei;XIANG Rongjun;LI Xinxin;LIU Yingjian(School of Mechanics and Civil Engineering,China University of Mining and Technology(Beijing),Beijing 100083,China;China Architecture Publishing&Media Co.,Ltd.,Beijing 100044,China;China Railway 16th Bureau Group Road&Bridge Engineering Co.,Ltd.,Beijing 101500,China)

机构地区：[1]中国矿业大学(北京)力学与建筑工程学院,北京100083 [2]中国建筑出版传媒有限公司,北京100044 [3]中铁十六局集团路桥工程有限公司,北京101500

出　　处：《桥梁建设》2024年第4期37-45,共9页Bridge Construction

基　　金：国家自然科学基金联合基金重点项目(U22A20244)。

摘　　要：为明确ECC(工程纤维增强型水泥基复合材料)-混凝土叠合梁抗弯性能及影响参数,并定性表征裂缝发展情况,设计、制作11根不同材料强度等级、配筋率、ECC层厚度、PVA纤维体积掺量的ECC-混凝土叠合梁及3根不同混凝土强度等级的混凝土梁进行四点弯曲试验,研究承载力、延性及裂缝发展等情况,并基于分形理论及数字图像处理技术,采用分形维数对不同影响参数下的叠合梁裂缝发展规律进行表征。结果表明:ECC-混凝土叠合梁较相同材料强度和配筋率的混凝土梁极限承载力和抗裂性能明显更优;材料强度等级提高,模型梁承载力及延性均提高;适筋范围内,配筋率越小模型梁延性越好;ECC层厚度对模型梁的承载力及延性影响不大;PVA纤维体积掺量为2.0%时,裂缝整体分布更均衡。计算分形维数得到的叠合梁表面裂缝分布具有自相似性;加载过程中叠合梁的分形维数小于混凝土梁,与试验结果相符,梁表面裂缝分形维数在一定范围内随着材料强度等级、配筋率、ECC层厚度、PVA纤维体积掺量的增加而降低,分形理论结合数字图像技术求得的裂缝分形维数可作为叠合梁裂缝分布及受弯损伤程度的定性表征指标。This study focuses on the flexural performance and influential parameters of the ECC(Engineering Cementitious Composites)and concrete composite girder,as well as the way to qualitatively characterize the crack propagation conditions.11 ECC-concrete composite girder specimens(composite specimens for short)with different parameters of material strength grade,reinforcement ratio,ECC layer thickness,PVA fiber volume as well as 3 concrete girder specimens(concrete specimens for short)with different concrete strength grade,were prepared for four-point flexural test,to study the load bearing behaviors,ductility and crack propagation.Based on the fractal theory and image processing technology,the fractal dimension was employed to characterize the crack propagation under different values of parameters.It is shown that the composite specimens exhibit better ultimate load bearing capacity and cracking resistant ability than the concrete specimens with same material strength and amount of reinforcement.Higher material strength leads to higher load bearing capacity and ductility of the specimens.When the volume fraction of PVA fibers is 2.0%,the overall distribution of cracks is more uniform.The surface cracks in composite specimens calculated by fractal dimension reveal self-similarity.During the loading process,the fractal dimension of composite specimens is smaller than that of ordinary concrete specimens,which is consistent with the experimental results.The fractal dimension of surface cracks decreases within a certain range with the increase of material strength grade,reinforcement ratio,ECC layer thickness,and PVA fiber volume fraction.The fractal dimension of cracks obtained by combined utilization of fractal theory and digital image technology can serve as a qualitative characterization index for crack distribution and the degree of bending damage of composite specimens.

关 键 词：ECC-混凝土叠合梁 PVA纤维体积掺量 承载力 延性 裂缝发展 分形维数 弯曲试验 

分 类 号：U448.216[建筑科学—桥梁与隧道工程]