FRP加固含缺陷钢结构的破坏力学分析

发布时间：2018-06-05 19:55

本文选题：碳纤维增强复合材料（CFRP） + 表面裂纹　；参考：《华南理工大学》2013年博士论文

【摘要】：纤维增强复合材料（FRP）的抗拉强度是钢的2-10倍，是一种被广泛应用的新型高性能材料。FRP加固钢结构技术，具有不产生次生应力和缺陷、耐久性好、施工方便、维护费用低等优点，备受工程界关注。然而，FRP加固含缺陷的钢结构中，除了构件加固前就存在的缺陷外，粘结层是最薄弱的部位，粘结层的破坏将导致FRP剥离，并最终造成整个加固结构的失效。为此，本研究针对FRP加固含缺陷钢结构的两个最薄弱部位：FRP与钢结构的粘结界面、以及缺陷体局部，分别以碳纤维板（CFRP板）与钢板试件的粘结界面、以及碳纤维薄板（CFL）加固钢板试件中的三维表面裂纹为研究对象，采用理论推导、数值分析与实验相结合的方法，对上述CFRP片材加固含缺陷钢结构的破坏机理进行力学分析。主要研究内容及结论如下： 1） CFRP与钢板的粘结界面应力计算公式的理论推导。建立了CFRP加固钢板的双剪模型，通过理论推导，给出了CFRP与钢板之间的界面剪应力和正应力、以及有效粘结长度等的计算公式，并讨论了界面剪应力的分布规律，探讨了剪应力与界面破坏机理的关联性。理论分析结果表明，钢板的几何尺寸、界面层的剪切模量和厚度、FRP片材和钢板的弹性模量、FRP片材的厚度等是界面粘结强度及影响加固效果的主要因素。 2）利用大型商用软件ANSYS，建立了CFRP板加固钢板的双剪有限元分析模型，模拟CFRP板加固钢板的双剪实验过程及其受力状态，重点探讨了实验过程中CFRP板与钢板之间的粘结界面的剪应力变化及分布情况，并将有限元的界面剪应力计算结果与本文提出的理论公式的计算结果进行了对比分析。计算结果表明，，界面剪应力的有限元计算结果与理论值基本吻合。这从一个侧面证明了本文提出的界面剪应力理论计算公式的有效性。 3） CFRP板加固钢板的双剪实验研究。采用ASTM D3166和ISO9644中推荐使用的Single Lap Joint型钢板与CFRP搭接接头，实施了CFRP板与钢板之间的粘结界面的双剪实验，测定了CFRP板与钢板之间的界面剪应力，分析了CFRP板与钢板粘结界面的应力分布、界面应力的传递特点，探讨了界面的粘结剪切破坏过程及破坏特征。研究结果表明， CFRP板与钢板之间的界面剪应力的实测结果与本文公式的理论计算值以及有限元计算结果都吻合得较好。这进一步验证了本文理论计算公式的有效性。 4） CFL加固受拉钢板中三维表面裂纹的应力强度因子的数值分析。首先，建立了三维半椭圆表面裂纹应力强度因子的有限元分析模型，探寻适合断裂力学分析的裂纹前缘网格划分的方法，优化模型及计算参数，并采用Newman-Raju公式验证了该数值方法的计算精度。然后，建立了受拉CFL加固含三维表面裂纹钢板的有限元分析模型，探讨了裂纹参数、加固方式和CFL参数对表面裂纹的应力强度因子的影响，提出了加固试件应力强度因子的半经验计算公式，探讨了拉伸载荷下CFL加固含缺陷钢结构的破坏机理。 5） CFL受弯加固钢板中三维表面裂纹的应力强度因子的数值分析。建立了受弯CFL加固含三维表面裂纹钢板的有限元分析模型，探讨了裂纹参数、加固方式和CFL参数对表面裂纹的应力强度因子的影响，提出了在弯曲载荷作用下加固试件应力强度因子的半经验计算公式，探讨了弯曲载荷下CFL加固含缺陷钢结构的破坏机理。研究结果表明，细长的浅裂纹是钢结构中最危险的缺陷，而采用FRP片材对含该类缺陷的钢结构进行加固是非常有效的先进技术。
[Abstract]:The tensile strength of fiber reinforced composite ( FRP ) is 2 - 10 times of that of steel . It is a widely used new type of high - performance material . The FRP - reinforced steel structure has the advantages of no secondary stress and defects , good durability , convenient construction and low maintenance cost .

1 ) The theoretical derivation of the calculation formula of bond interface stress between CFRP and steel plate is deduced . The calculation formula of interfacial shear stress and positive stress and effective bond length between CFRP and steel plate are deduced . The relationship between shear stress and interface failure mechanism is discussed . The theoretical analysis results show that the geometric dimension of the steel plate , the shear modulus and thickness of the interface layer , the elastic modulus of FRP sheet and steel plate , the thickness of FRP sheet and so on are the main factors influencing the bonding strength of the interface and the effect of reinforcement .

2 ) Based on ANSYS , a double shear finite element analysis model of CFRP sheet reinforced steel plate is established . The shear stress variation and distribution of the bond interface between CFRP plate and steel plate are simulated . The results show that the calculation results of the interface shear stress are in agreement with the theoretical formula . The results show that the calculation formula of interfacial shear stress is valid .

3 ) The double shear experiment of the CFRP plate strengthened steel plate was carried out . Using the single Lap joint type steel plate and the CFRP lap joint as recommended in ASTM D3 166 and ISO9644 , the interfacial shear stress between the CFRP plate and the steel plate was measured . The stress distribution of the interface between the CFRP plate and the steel plate was measured . The experimental results show that the measured results of the interface shear stress between the CFRP plate and the steel plate are in good agreement with the theoretical calculation value and the finite element calculation result of the formula .

4 ) The numerical analysis of the stress intensity factors of the three - dimensional surface crack in the tensile steel plate is analyzed . First , the finite element analysis model of the crack - stress intensity factor of the three - dimensional semi - elliptical surface is established , and the calculation precision of the numerical method is verified by using the Newman - Raju formula .

5 ) Numerical analysis of the stress intensity factors of three - dimensional surface cracks in a steel plate subjected to bending reinforcement is established . The finite element analysis model of the crack parameters , the reinforcement mode and the CFL parameters on the stress intensity factors of the surface crack is established . The failure mechanism of the CFL on the defective steel structure under the bending load is discussed . The results show that the slender shallow crack is the most dangerous defect in the steel structure , and the FRP sheet is used to reinforce the steel structure containing the defect .
【学位授予单位】：华南理工大学
【学位级别】：博士
【学位授予年份】：2013
【分类号】：TU391;O346.1

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