【作者】 杨小兵；

【导师】 侯建国；

【作者基本信息】 武汉大学 ， 结构工程， 2004， 硕士

【摘要】 收缩和徐变是混凝土材料本身固有的时变特性，正确的估计和预测收缩徐变对大型预应力混凝土桥梁(尤其是城市轻轨高架桥梁中的预应力混凝土箱梁)的反拱和挠度及长期变形的影响，是我国当前城市轨道交通建设工程设计与施工中急待研究解决的问题。国内对混凝土收缩徐变预测模型虽然已经开展过一些研究，但限于当时的技术水平和条件，所建立的混凝土收缩徐变预测模型过于粗略，难以适应我国现代混凝土结构和大型预应力混凝土结构的发展要求，急需改进。 本文根据已收集到的国内外混凝土收缩徐变研究的文献资料和最新研究进展情况，详细讨论了混凝土收缩徐变的物理机理和影响因素，为建立较为合理的混凝土收缩徐变预测模型奠定了坚实的理论基础；比较研究了建科院(1986)模型、CEB-FIP系列模型、ACI 209系列模型、BS系列模型、B-P系列模型、GZ(1993)模型和GL 2000模型等国内外常用的混凝土收缩徐变预测模型的理论基础、考虑的因素及与试验数据符合的程度，基本上摸清楚了各种模型的特点和存在的不足；在此基础上，参考国内混凝土收缩徐变试验研究的主要成果——建科院(1986)模型，提出了混凝土收缩徐变预测的建议模型；按照能量原理和有限元的基本理论，推导了同时考虑混凝土收缩和徐变的有限元计算的基本方程，编制了相应的预应力混凝土桥梁收缩徐变分析程序CAPB(Creep Analysis Programme for Bridge of Prestressed Concrete)，分别采用本文建议的混凝土收缩徐变预测模型和桥梁规范JTJ 023-85采纳的CEB-FIP(1978)模型，对武汉市轻轨一号线一期工程中的预应力箱梁的收缩徐变变形进行了计算，并将计算结果与原型观测结果进行了比较。文章最后对所作的工作进行了总结，并就今后值得进一步研究的问题和研究方向进行了展望。 本文研究的主要成果有： (1) 通过对混凝土收缩徐变机理和影响因素的分析，认为构件体表比主要是对混凝土收缩和徐变的发展进程产生较大影响，其对混凝土收缩和徐变的影响程度与时间有关，在建立混凝土收缩徐变预测模型时，应将其放在时间函数中考虑；混凝土的抗压强度虽然与混凝土的收缩徐变没有直接的关系，但间接反映了混凝土水灰比和水泥用量对混凝土收缩和徐变的影响。鉴于当前实际工程中的混凝土强度等级有较大提高，建议在混凝土的收缩徐变预测模型中考虑混凝土强度等级的影响。 (2) 对国外几种典型的混凝土收缩徐变预测模型的对比研究发现，在ACI 209R(1992)模型、CEB-FIP(1990)模型、RILEM B3(1995)模型和GL2000模型这四种国外较新的预测模型中，整体上与试验数据符合最好的是GL 2000模型，其次是RILEMB3(1995)模型和eEB一FIP(1990)模型，ACI 209R(1992)模型表现最差。因此，在缺乏试验资料，需要引用国外模型对混凝土结构和预应力混凝土结构进行收缩徐变计算时，推荐采用GL 2000模型和RILEM B3(1995)模型。 (3)通过对混凝土收缩徐变的产生机理和影响因素及国内外预测模型的综合研究，提出了混凝土收缩徐变预测的建议模型。理论分析和国内实测资料验证表明，建议模型的物理概念清楚，公式形式简单，实用方便，考虑的因素比建科院(1986)模型及桥梁规范JTJ 023一85采用的CEB一FIP(1 978)模型全面，对混凝土收缩徐变的预测精度较高。 (4)推导了同时考虑混凝土收缩和徐变的有限元计算的基本方程，采用本文建议的混凝土收缩徐变预测模型，用FORTRAN语言编制了预应力混凝土桥梁收缩徐变分析的电算程序CAPB，程序使用方便，运行快速稳定，计算结果可靠。 (5)采用本文编制的程序CAPB，对武汉市轻轨一号线一期工程中的预应力箱梁的收缩徐变变形进行了计算，得到了预应力箱梁在不同时刻的变形数据。并与原型观测结果及采用桥梁规范JTJ 023一85采纳的cEB一FIP( 1 978)模型的计算结果进行了比较，结果表明，采用本文建议的预测模型的计算结果与实测结果吻合程度更好一些。从计算结果可知，箱梁施加预应力后3个月左右的变形已基本趋于稳定，与箱梁的原型观测结果一致，从理论上证实了设计单位关于箱梁的变形在预应力施加后3个月左右即趋于稳定可以铺轨施工的推测，为保证轻轨一号线一期工程于2002年11月按期进入铺轨施工提供了科学依据和重要参考。 上述研究成果不仅为大型预应力混凝土桥梁的收缩徐变预测提供了一个方便实用的工具，而且对于推动我国混凝土收缩徐变研究的进一步开展也具有重要的理论意义和实用价值，可供我国预应力混凝土桥梁等相关设计规范今后修订时参考。更多还原

【Abstract】 The shrinkage and creep are the inherent time-dependent characteristics of concrete materials. It is urgent to accurately estimate and predict the influence of concrete shrinkage and creep on the deflections of large-scale prestressed concrete bridges (especially the prestressed box-sectional beams in light rail trestle projects). The research on prediction model of concrete shrinkage and creep has been paid less attention at home, and the current model can’t meet the requirement of modern concrete and prestressed concrete structures. The introduction about the finite element method considering shrinkage and creep of concrete is mostly sketchy, and the factors taken into account are not comprehensive, which goes against widely applications of the method. The reasonable construction time for tracklaying after completing the civil work of the Wuhan Light Rail Trestle Project has to be confirmed. Those problems urgently need to be resolved through some special research work.The mechanisims and influential factors, as well as the newly research findings, are firstly expatiated before the factors that should be involved in a reasonable prediction model are clarified. Then the the main characteristics and disadvantages of the current prediction models at home and abroad are clear understood, after the detailed comparison and commentary on the theoretical principle, factors considered and the fitting precision to the test data of those models are carried out. Based on the foregoing research and the ASRI (1986) model, which sumarried the main results of the domestic experimental research, a prOpositional prediction model for the shrinkage and creep of concrete is developed by the author. In addition, the basic equation of the age-adjusted finite element method considering shrinkage and creep of concrete in the same time is derivated by means of the energy principle before the calculation procedures of the FEM are presented. Finally, the according computer programme CAPB is compiled, to calculate the creep displacements of some partial prestressed box beams of the Line one in the first stage of the Wuhan Light Rail Trestle Project adopting the propositional model and CEB-FIP (1978) model respectively, and the calculation results are compared with the prototype observed data.Through the foregoing research work, the major findings are as follows:(1) By analyzing the mechanisims and influential factors of concrete shrinkage and creep, it is deemed that the member volumn-surface ratio have a significant impact on the developing process rather than the ultimate value of that. The compression strength of concrete have no direct relation to shrinkage and creep, but it can reflect the influences ofwater-cement ratio and cement content on shrinkage and creep, and it should be take into account in the predition model with the enhancement of concrete compression strength of current structures.(2) Comparison research indicate the GL 2000 model performs best for predicting shrinkage and creep, followed by RILEM B3 (1995) model, CEB-FIP (1990)model and ACI 209R (1992) model, among the four neoteric prediction models. So the GL 2000 model RILEM B3 (1995) model are firstly recommended in case of lack of test data and the overseas models have to be chosen.(3) Based on the comprehensive research on the mechanisims, influential factors and prediction models of concrete shrinkage and creep, a prepositional prediction model for the shrinkage and creep of concrete is developed by the author. The prepositional prediction model reveals explicit concept, considers more factors and has a better prediction precision than the ASRI (1986) model or the CEB-FIP(1978)model adopted by the design code JTJ 023-85.(4) The basic equation of the age-adjusted finite element method considering shrinkage and creep of concrete in the same time is derivated by means of the energy principle, and the shrinkage and creep analysis computer programme CAPB for prestressed concrete bridges, which involves the author’s prepositional prediction model, is co更多还原