【作者】 车轶；

【导师】 宋玉普；

【作者基本信息】 大连理工大学 ， 结构工程， 2002， 博士

【摘要】 拱坝的孔口附近区域在坝体自重、库水压力、孔内水压、温度和徐变等多种作用影响下会产生较大的拉应力，从而导致孔边混凝土开裂，对大坝的整体安全性造成影响，因此须进行配筋。传统的配筋方法是采用弹性理论计算孔口周围的应力分布，用应力图形法进行孔口的配筋计算。这种方法不能反映混凝土和钢筋两种材料的非线性性质以及混凝土开裂后引起的应力重分布，并且不能有效地控制孔口的开裂，按照此方法计算的配筋量往往偏大。本文采用试验研究与计算分析相结合的研究方法，结合小湾工程，对拱坝底孔在不同工况下的应力分布、混凝土开裂、裂缝扩展和孔口破坏规律，以及配筋方式、数量对其影响进行了研究，并利用有限元方法对采用钢纤维混凝土提高孔口的抗裂性能和限裂性能进行有益的探讨，为安全可靠、经济合理地设计拱坝孔口提供理论依据。本文的主要工作有： 1)通过17块带圆孔钢筋混凝土板的试验，研究在荷载作用下孔口周围混凝土和钢筋的应力应变分布和孔口开裂、破坏规律，以及不同的配筋方式和数量对孔口混凝土裂缝的产生、发展及孔口破坏的影响，为验证有限元分析模型及非线性分析程序的可靠性提供试验依据，并为建立新的孔口配筋设计方法提供基本试验资料。 2)采用非线性有限元方法对试验模型进行分析，通过试验结果与数值分析结果的比较，验证有限元模型及分析程序的可靠性，并利用数值分析手段进一步研究孔口的开裂、裂缝扩展规律。 3)基于钢筋混凝土间的粘结应力分布函数，推导了开裂后的钢筋混凝土轴拉构件的应力应变关系，建立了开裂分析模型，并通过引入钢筋混凝土构件开裂强度表达式，考虑了混凝土应力在构件纵、横两个方向不均匀分布对钢筋混凝土构件开裂的影响。将该一维模型进一步推广至二维钢筋混凝土有限元模型中，并利用该模型对试验模型进行了数值分析。该模型不仅有效地反映了配筋率、裂缝间距以及钢筋和混凝土材料特性等因素对钢筋混凝土开裂后性能的影响，并且很容易在现有的有限元程序中实现。 4)对小湾拱坝的1~#底孔进行了三维非线性分析，研究了孔口在坝体自重、库水压力、孔内水压力和库水温度影响等作用下的孔口应力分布、混凝土开裂、裂缝发展规律以及配筋对孔口开裂和裂缝扩展的影响。由于孔口与大坝体型相差悬殊，在分析中采用了子模型法。利用该方法不仅大大节省了计算时间，而且降低了网格剖分的难度。 5)对1~#底孔在最不利工况下的不同断面，考虑不同的配筋情况，进行了二维非线性分析。根据模型试验和二维、三维非线性分析结果，提出了新的拱坝孔口结构配筋公式。其形式基本与线弹性配筋公式保持一致，沿用线弹性方法进行计算，通过配筋的调整系数来考虑钢筋和混凝土非线性性质影响。 6)根据已有的钢纤维混凝土基本理论和试验研究成果，建立了钢纤维混凝土(SFRC)的有限元模型，对小湾拱坝的1~#底孔断面进行了非线性分析，研究了 大连理工大学博士学位论文 采用不同厚度的钢纤维混凝上增强层和不同掺量的钢纤维对孔口抗裂、限裂性 能的影响。更多还原

【Abstract】 Deadweight of dam, hydraulic pressure, temperature and concrete creep can result in high local tensile stress near the orifice in arch dams, which lead to concrete cracking. It can affect the safety of the arch dam, so steel bars are needed near the orifice.By traditional method of design, the elastic theory is adopted to calculate stress distribution, and the amount of reinforcing bars for the orifice is determined according to the diagram of tensile stress. By this means, nonlinear properties of concrete and steel bars, as well as stress redistribution near the orifice caused by concrete cracking, are not taken into account. Furthermore, concrete cracking could not be well controlled by reinforcing bars. It is shown that the amount of steel bars is overestimated.In this thesis, stress distribution, concrete cracking and its propagating, and failure mechanism of the orifice of the Xiao Wan Arch Dam, as well as the influence of reinforcing bars are studied by both experimental tests and nonlinear analysis. Also, the improvement of the performance of the orifice in cracking control by using steel fiber reinforced concrete is studied. These works are useful for the design of the orifice in arch dams. The details are as following:1) Through the experiments of seventeen reinforced concrete plates with round openings, stress distributions of concrete and steel bars, concrete cracking, failure mechanism, and the influence of reinforcing bars with different amount and layouts on cracking and failure mechanism of the specimens are studied. The experimental study provides data not only for the validation of FEA model and nonlinear FEM program, but also for the research on new methodology of design for orifices.2) Nonlinear finite element analysis on the specimens is performed. The FE model and the FE program are validated by experimental results. The mechanism of concrete cracking and crack propagating is also studied by using finite element method.3) Based on the bond stress distribution function at the concrete-steel interface, a stress-strain relationship for cracked reinforced concrete tensile members is derived, and thereby an analytical model is proposed. By introducing a crack strength expression, the influence of non-uniform distribution of concrete stress in transverse and longitudinal directions in a reinforced concrete tensile member on concrete cracking is taken into account. A two-dimensional model, which is derived from the one for tensile members, is applied to the analysis of the experimental specimens. It is shown that the proposed model can not only take the ratio of reinforcement, the material properties of reinforcement and concrete and the crack spacing into account, but also be easily incorporated in finite element programs.4) Three-dimensional nonlinear analysis of the bottom outlet of the Xiao Wan Arch Dam is presented using sub-model techniques. The structural characteristics and failure mechanism of the bottom outlet, under loading of concrete deadweight, hydraulic pressure, internal water pressure and temperature are studied. It is shown that the meshing of the structure becomes easy and the computing time is reduced by using sub-modeling method.Ill5) Two-dimensional analysis on different sections of the orifice with reinforcing bars in variety of amount and layouts is carried out. A new formula for the calculation of reinforcing bars of the orifice is proposed, based on experimental and two and three dimensional analysis. The proposed formula is in accordance with the old one, and the affect of nonlinear material properties of concrete and steel bars is considered by an adjusting coefficient.6) Based on theoretical and experimental research on material characters of steel fibered reinforced concrete, a finite element model for nonlinear analysis of steel fiber reinforced (SFRC) structures is presented. Two-dimensional analysis on various sections of the orifice in the Xiao Wan Arch Dam is carried out. The influence of SFR更多还原