【作者】 黄羽立；

【导师】 叶列平；

【作者基本信息】 清华大学 ， 土木工程， 2005， 硕士

【摘要】 由于具有轻质高强、施工方便和耐腐蚀性强等特点,纤维增强复合材料(Fiber-Reinforced Polymer,简称FRP)在土木工程中得到越来越广泛的应用。其中一项重要的用途就是通过缠绕FRP提供的约束来加固修复钢筋混凝土柱,FRP约束钢筋混凝土柱的抗压强度和延性都得到很大的提高。 本文提出一个新的FRP约束混凝土分析模型,在模型中,核心混凝土、约束材料以及它们之间的相互作用都可以通过显式计算进行模拟。本分析模型采用了一个新的侧向应变公式,这个侧向应变公式是经过对未约束混凝土,主动约束混凝土以及FRP布约束混凝土的试验结果分析总结而提出的,因此更精确,适用性更广泛。和现有大量FRP布约束混凝土试验的比较,说明本模型的预测是准确的。对于预应力FRP约束混凝土,以及钢管约束混凝土的准确预测则说明了本模型对于其他特性材料约束的混凝土,也有相当广泛的适用性和可拓展性。与试验数据的比较结果还说明,本模型优于现有的分析模型。 本文搜集了常用商业有限元程序中的混凝土本构模型,对它们的构成要素进行了分类,这些要素包括剪切强度和损伤累积、剪切强化准则、塑性流相关程度和帽盖及其形状。通过各要素在单轴压缩、静水压缩、单轴应变压缩以及三轴压缩等基本应力路径下数值模拟中的异同,分析了这些要素的作用和影响:单轴压缩试验说明了剪切强化准则和塑性流关联程度的重要性;静水压缩和单轴应变压缩试验分别展示了帽盖和帽盖形状的影响;而三轴压缩试验则分析了模型中剪切强度和损伤累积与静水压力相关的必要性。最后,本文以FRP约束混凝土为例,指出一个本构模型要全面准确的模拟约束混凝土的受压性能,必须包含剪切和体积压缩两方面的弹塑性关系。按照这个指导方针,选择了合适的混凝土本构模型对FRP约束混凝土方柱进行有限元分析,与试验结果的比较说明,有限元分析结果在应力应变各量都与试验结果吻合良好。更多还原

【Abstract】 Fiber reinforced polymer (FRP) composites have found increasingly wide applications in civil engineering due to their high strength-to-weight ratio, high corrosion resistance and easy installation. One important application of FRP composites is as a confining material for concrete. FRP confinement can enhance both the compressive strength and the ultimate strain of concrete significantly.This paper presents a new analysis-oriented stress-strain model for FRP-confined concrete in which the responses of the concrete core and the FRP jacket as well as their interaction are explicitly considered. The key novel feature of the proposed model is a more accurate and more widely applicable lateral strain equation based on a careful interpretation of the lateral deformation characteristics of unconfined, actively confined and FRP-confined concrete. Through comparisons with independent test data, the proposed model is shown to be accurate not only for FRP-confined concrete but also for prestressed-FRP-confined concrete, and concrete confined with a steel tube, demonstrating the wide applicability of the model to concrete confined with different confining materials. The accuracy of the proposed model is also shown to be superior to existing analysis-oriented stress-strain models through comparisons with test data.This paper also presents an overview of commercially available constitutive models for concrete, highlighting their application to FRP-confined concrete. The components of these models are categorized as shear strength and damage accumulation, hardening rule, flow rule associativity and the type of cap. The influences of these components are addressed through their evaluation in numerical experiments including uniaxial stress compression, hydrostatic compression, uniaxial strain compression and triaxial compression. Uniaxial stress compression will show the significance of hardening-softening plasticity and appropriate flow rule associativity. Hydrostatic compression and uniaxial strain compression will show the influence of the cap and type of cap respectively. Triaxial compression test will shown the necessarily of pressure-dependent shear strength and damage accumulation. Highlighting their ap-plication to FRP-confined concrete, it is shown that representation of both pressure-dependent plastic deviatoric and plastic volumetric behaviors are necessary to model confined concrete comprehensively. According to this policy, an appropriate constitutive model is chosen to conduct a finite element analysis of FRP-confined rectangular column. Good agreements have been found in comparisons on stress and strain history.更多还原