【作者】 李庆华；

【导师】 徐世烺；

【作者基本信息】 大连理工大学 ， 结构工程， 2009， 博士

【摘要】 南水北调工程重要输水建筑物如长距离输水隧洞、大型输水渡槽的安全性对整个输水工程的安全运行至关重要。从结构设计选材方面应做到确保满足南水北调重大工程结构抗裂防震要求,最大限度降低甚至免去维护和加固费用,从根本上保证重大基础设施的安全运行。结合国家自然科学基金重点项目(50438010)和南水北调工程重大关键技术研究及应用项目(JGZXJJ2006-13),本论文以超高韧性水泥基复合材料(UHTCC)这一新型绿色结构材料为基础,开展了向新材料结构方向迈进的探索性工作,旨在建立配筋超高韧性水泥基复合材料受弯构件计算新理论,提出一种具有防裂抗震和优异耐久性能的新材料复合结构。为实现此目的,主要开展了如下研究工作:1.针对水工混凝土大跨薄壳结构的开裂问题、腐蚀环境下的钢筋混凝土结构维修和加固问题,结合纤维编织网与UHTCC二者的优势,开展了非金属筋(碳纤维编织网)增强超高韧性水泥基复合材料的力学性能试验研究。通过11组碳纤维编织网增强UHTCC(CTRUHTCC)薄板四点弯曲试验(试件尺寸400 mm×100 mm×10 mm)和拔出试验(试件尺寸140mm×60mm×10mm)研究,分析了基体水胶比、纤维编织网表面处理方法、基体PVA纤维掺量对CTRUHTCC裂缝开展形态、承载能力和粘结性能的影响,发现采用环氧树脂浸渍碳纤维编织网之后进行表面粘砂是改善碳纤维编织网与基体之间粘结性能的实用方法。2.利用UHTCC材料显著的非线性变形能力、出色的力学特性和与钢筋的变形协调性以及优异的裂缝控制能力,针对UHTCC在抗震限裂要求严格的大跨度结构或结构变形关键部位使用时遇到的构件设计问题,开展了钢筋增强超高韧性水泥基复合材料受弯构件即RUHTCC长梁的弯曲性能研究。基于材料的力学本构模型和平截面假定,建立了配筋UHTCC受弯构件的计算模型,对加载至最终破坏各阶段内力变化进行了详细的分析,给出了加载至破坏整个过程的弯矩-曲率关系的确定方法,以及延性指标和跨中挠度的计算公式。提出了相关配筋计算公式以供工程使用参考。3.进行了3组共12根不同配筋率的无腹筋大跨度RUHTCC梁(试件尺寸2450 mm×120 mm×80 mm)四点弯曲试验研究,验证了本文所提出的配筋UHTCC受弯构件计算模型的合理性。通过与3根普通钢筋混凝土梁的对比发现,RUHTCC梁破坏模式更具韧性特征,UHTCC材料能够明显的延缓钢筋的屈服,提高结构或构件的承载力,降低构件对截面尺寸和配筋率的要求,从而减轻结构自重,降低工程造价。使用电阻应变片法和裂缝观测仪观察了梁的起裂和裂缝扩展,发现RUHTCC梁具有卓越的裂缝控制能力,在正常使用状态下,裂缝宽度可以保持在0.05mm以内。4.提出了RUHTCC的简化计算方法以便于实际工程设计使用;确定了RUHTCC的界限配筋率和最小配筋率的取值以及变形和截面曲率延性系数的计算方法,发现当UHTCC拉伸应变能力较高时无需最小配筋率的限定;分析了截面几何尺寸、材料性能参数和纵筋配筋率对RUHTCC受弯梁的承载力、变形和延性的影响。5.根据功能梯度这一概念,利用UHTCC优秀的裂缝控制能力,使用UHTCC材料代替部分混凝土作为钢筋保护层制备了控裂功能梯度复合梁(UHTCC-FGC),以提高钢筋混凝土结构的耐久性。对整个加载过程中复合梁的内力变化和裂缝开展进行了探讨,给出了加载至破坏整个过程的弯矩-曲率关系的确定方法,以及跨中挠度、截面延性指标的计算公式。6.通过4组共16根不同厚度UHTCC保护层的UHTCC-FGC梁(试件尺寸2450mm×120 mm×80 mm)四点弯曲试验结果验证了理论计算公式的正确性。对UHTCC-FGC梁的承载力-变形关系曲线和裂缝开展形态进行了分析讨论,并与3根钢筋混凝土对比梁进行了比较。应用应力叠加的方法以及耐久性方面考虑,得到了UHTCC-FGC梁中UHTCC保护层的最佳厚度确定方法。更多还原

【Abstract】 Security of critical conveyance structures,such as long-distance water conveyance tunnels and large-scale aqueduct structures is vital to the normal operation of South-to-North Water Transfer project.Structural design and material selection are so important that the requirements of crack resistance and earthquake protection should be satisfied from these two aspects,to reduce or even eliminate maintenance and repair expense,and guarantee the safe operation of foundational establishment.On the basis of ultra high toughness cementitious composite(UHTCC),a new kind of green structural material,exploratory research work on new material structures is carried out in the present research,to establish calculation theory of reinforced UHTCC flexural members and propose an aseismatic,crack-reesistant and durable new material composite structures.And this research is part of the Key Program of the National Natural Science Foundation of China(No.50438010) and the Research and Application Programs of Key Technologies for Major Constructions in the South-North Water Transfer Project Construction in China(JGZXJJ2006-13).In orter to perform the aim mentioned above,the details are as follows:1.Combining both advantages of carbon textile and UHTCC,research on thin UHTCC components reinforced with carbon textile(CTRUHTCC) is carried out.It takes a fire-new choice of structural materials for crack-resistance of large-span shell structures in hydraulic engineering and can be used in maintenance and strengthening of reinforced concrete structures under exposed environment.Compared with textile reinforced mortar,influences of the surface treatment of carbon textile,water-binder ratio,volume content of polyvinyl alcohol(PVA) fiber on crack resistance,load bearing capacity and bond property of the tested composite have been investigated through four-point bending experiments and pull-out tests. Eleven series of specimens are used for the both experiments.The specimen dimensions are 400 mm×100 mm×10 mm for four-point bending test,and 140mm×60mm×10mm for pull-out test.The proposed approach for surface treatment of carbon textile by spreading sands on the surface of carbon roving impregnated with an epoxy resin is found to be a practical method that obviously improves bond properties between textile and UHTCC matrix. 2.By making use of prominent non-linear deformation capacity,excellent mechanical performances,compatible deformation ability with steel reinforcement and outstanding crack-resistance of UHTCC,investigations on flexural behavior of reinforced UHTCC (RUHTCC) long flexural members are carried out.Based on mechanical constitutive models of materials and plane section assumption,theoretical calculation model of RUHTCC flexural members is established and detailed analysis on development of internal forces during the whole bending process is also presented.Moreover,determination of moment-curvature relation and theoretical formulae of deflection and curvature are given in the present research.3.Three series of RUHTCC long beams without web reinforcement are tested through a four-point bending experiment to verify theoretical formulae of RUHTCC flexural members proposed in the present research.It is discovered that for RUHTCC beams,plane-section assumption is tenable.Totally,there are twelve RUHTCC beams with three different reinforcement ratios and three ordinary reinforced concrete beams as reference specimens in the test,and the dimensions of them are 2450 mm×120 mm×80 mm.Compared with reference specimens,yielding of reinforcement can be delayed in RUHTCC beams,and the failure pattern of RUHTCC specimens represents a ductile response,ensuring the safety and reliability of structures in seismic protection.UHTCC can continue undertaking tension load after cracking due to the strain-hardening feature,therefore,load bearing capacity and ductility of structures or components can be improved and steel products can be saved. Electric resistance strain gauges and a crack width measurement instrument with a 40×lens are used to monitor the propagation of crack and development of crack width.It is found that crack width in RUHTCC beams is limited to 0.05mm under service load conditions and can be considered without negative influence on durability.4.Simplified calculation method of RUHTCC flexural member is proposed for convenience.The critical reinforcement ratio,the minimum reinforcement ratio,deflection and curvature ductility index are also deduced.It is found that there is no need to limit the minimum reinforcement ratio when the tension strain capacity of UHTCC is high enough. Influence factors of flexural capacity and ductility,including geometric dimensions,material parameters and reinforcement ratio,have been investigated in the present research on the basis of theoretical equations.5.Investigations on bending behavior of functionally-graded composite beam crack controlled by UHTCC(UHTCC-FGC) are carried out to improve durability of reinforced concrete structures.Based on the concept of functionally graded concrete,UHTCC with excellent crack-controlling ability is strategically substituted for part of the concrete,which surrounds the main longitudinal reinforcement in a reinforced concrete member.The thesis discusses the development of internal force and crack propagation during loading process,and presents analysis of moment-curvature relationship from loading to damage and calculation of mid-span deflection and ductility index.6.Theoretical formulae are validated through experimental results of sixteen UHTCC-FGC beams with four different thicknesses of UHTCC layer.The dimensions of specimens are 2450 mm×120 mm×80 mm.Moment-curvature relation and crack pattern of UHTCC-FGC beams are discussed in comparison with three ordinary reinforced concrete beams.In addition to improving bearing capacity,the results indicate that UHTCC-FGC beams have been found to be very effective in preventing corrosion-induced damage,At last, the optimal thickness of UHTCC layer in UHTCC-FGC beams has been confirmed through stress superposition and in consideration of durability.更多还原