ECC加固钢筋混凝土结构受剪性能及精细化数值分析方法研究

The shortage of theoretical study and effective numerical simulation method are the bottle-neck problems in the application of ECC used for strengthening existing RC structure. In this project, shear stress transfer model of crack surface in strengthened RC structure was created through studying shear stress transfer capacity of crack surface, and fine numerical method for analyzing shear performance of strengthened RC structure was developed. After that, the shear failure mechanism of strengthened RC structure under static load and cyclic load was revealed using numerical simulation, theoretical and experimental studies, and the theory on shear performance of strengthened RC structure was also improved, which could promote the application of ECC used for strengthening RC structure. In the process of creating aforementioned shear stress transfer model, the shear lattice system was built for describing the shape of crack surface in strengthened RC structure based on measuring the roughness of crack surface; the contributions for shear stress transfer of crack surface in strengthened RC structure were also clarified, which were from contact stress in compression part of concrete structure and ECC strengtheing layer, and fiber bridging stress in tension part of ECC strengtheing layer. Moreover, the varied ductility of ECC strengtheing layer due to existing cracks in RC structure was quantified based on the established applicable numerical model, which was the prerequisite variable before studying the shear stress transfer capacity of crack surface in strengthened RC structure, since the shear stress transfer occurred in crack surface of ECC strengtheing layer after cracking .

针对ECC在加固钢筋混凝土结构应用中存在的理论研究不足、缺少有效数值分析方法等瓶颈问题，通过研究ECC加固钢筋混凝土结构裂缝面剪力传递能力，建立加固结构裂缝面剪应力传递模型，形成分析ECC加固钢筋混凝土结构受剪性能的精细化数值方法，并与理论推导及试验研究相结合，揭示静载及反复荷载作用下加固结构受剪破坏机理，完善加固结构受剪性能相关理论，推动ECC用于钢筋混凝土结构加固。研究基于实测的加固结构裂缝面凹凸程度，建立描述裂缝面形态的剪切格子体系；通过数值模拟与面内纯剪试验，阐明钢筋混凝土结构裂缝面压缩侧接触作用、ECC加固层裂缝面压缩侧接触作用及拉伸侧纤维架桥作用分别对加固结构裂缝面剪应力传递的贡献，进而建立前述加固结构裂缝面剪应力传递模型。此外，通过建立实用的数值模型，定量明确钢筋混凝土结构既有多条裂缝引起ECC加固层延性的变化，为前述加固结构裂缝面剪力传递能力研究提供前提条件。

混凝土结构在极端荷载或正常荷载作用下因延性或耐久性不足易受损。ECC具有高延性、高耐久性、可持续等优势，采用ECC可显著提高加固混凝土结构延性和耐久性。然而，ECC独特的高延性及多缝开裂等特征，使得ECC加固混凝土结构剪切破坏机理尤为复杂，且缺少有效分析方法。本项目在研究混凝土结构既有裂缝引起ECC加固层延性变化机理、ECC加固钢筋混凝土结构剪力传递机理基础上，形成用于分析ECC加固钢筋混凝土结构受剪性能的精细化数值方法。在此基础上，通过数值模拟、试验与理论手段，研究ECC加固钢筋混凝土结构受剪性能及破坏机理。钢筋增强ECC构件受弯性能试验研究表明ECC延性变化具有尺寸效应，且钢筋有助于提高ECC构件多缝开裂行为；ECC双侧面加固RC构件受剪性能试验研究表明，加固构件的抗剪承载力随着ECC加固层厚度的增加而显著增加，且抗剪承载力与加固层厚度呈线性增加趋势。研究提出用于定量分析ECC裂缝面张开后纤维架桥作用对剪应力转移贡献的ECC双面纯剪试验，得到ECC裂缝面分离前裂缝面剪应力转移受压缩侧接触作用与拉伸侧纤维架桥作用共同影响，但ECC裂缝面分离后裂缝面剪应力转移取决于拉伸侧纤维架桥作用。研究提出RC结构既有裂缝引起ECC加固层延性变化数值模型，可以准确反映不同厚度ECC加固层细小裂缝扩展模式及ECC加固层延性变化，进而提出ECC受弯加固RC构件简化数值分析方法，解析结果准确且与单元尺寸无关。研究提出ECC受剪加固混凝土结构数值分析方法，所包含的ECC裂缝面剪应力转移模型可分别定量考虑裂缝面基体接触作用及纤维架桥作用对ECC加固层受剪性能影响。本项目的完成有助于推动ECC用于钢筋混凝土结构加固。