【作者】 钮鹏；

【导师】 杨刚；

【作者基本信息】 大连海事大学 ， 道路与铁道工程， 2011， 博士

【摘要】 现代建筑提倡使用绿色建筑材料,钢结构材料得以广泛利用。钢结构中大多存在压弯构件,此类构件的破坏形式有强度破坏或者失稳破坏,而后者一直备受人们关注。研究失稳破坏问题大多采用数值方法。对于截面相对比较简单,受力情况又不十分复杂的构件,则可以寻求解析方法求解。本文将基于计算压弯构件弹塑性失稳的解析求解思想,推导在轴压和弯矩共同作用下翼缘外表面粘贴碳纤维的H型钢构件和方矩形(空心)截面钢构件及表面全部粘贴碳纤维的圆形截面钢管构件增强前后绕强轴失稳时的极限荷载计算公式,同时给出了有限元数值分析结果。求解中分别对两端简支压弯钢构件失稳时截面受压侧屈服和受压受拉侧均屈服的两种情况进行了讨论。对于H型钢构件和方矩形(空心)截面钢构件来说,又可进一步分别考虑屈服区出现在翼缘和腹板内的情形。而对于圆形截面钢管构件来说,由于管壁较薄,不再考虑塑性区沿壁厚的变化。给出了翼缘外表面粘贴碳纤维且具有初始几何缺陷的压弯H型钢的极限承载力表达式。分析比较了碳纤维对具有初始几何缺陷的钢构件和完善构件增强效果。当两端给定不同弯矩值时,增强后具有初始缺陷的钢构件与未增强的完善构件极限承载力进行对比,获得碳纤维增强效果的结论。理论求解残余应力在稳定问题中的影响相对比较困难,故本文利用有限元软件模拟分析了两端简支具有初始残余应力压弯H型钢构件的失稳问题。详尽讨论了碳纤维增强前后H型钢构件在给定残余应力模式下,极限承载力随两端弯矩改变的变化规律,特别提出了复合材料在端弯矩较大时的增强作用。通过给出具有不同长细比压弯H型钢构件失稳时的极限承载力,截面弹性核高度等参数,得到与钢结构设计规范一致的弯矩与极限承载力相关曲线。做出相应的增强后压弯H型钢构件的极限承载力与弯矩相关曲线,并得到实用的极限承载力实用公式。分别列举其它截面尺寸增强前后H型钢构件极限承载力与弯矩相关曲线来验证简化公式的正确性,并为工程设计提供参考。对碳纤维增强前后就两端在不同弯矩作用下存在冲击荷载、循环荷载的H型钢构件进行了非线性动力屈曲分析,分别给出了增强前后钢构件的冲击后的极限屈曲荷载和循环水平极限荷载值,最后讨论了边界条件,碳纤维厚度和弹性模量对存在动力荷载作用下H型钢构件的影响。更多还原

【Abstract】 Modern buildings advocate taking advantage of the green building materials, so the steel structural is used extensively. The failure modes of many members subjected to axial compressive forces and bending moments in steel structure are intensity or stability damage, the latter of which is the most interesting question concerned by people. Generally these problems are solved by some numerical methods. To deal with the above-mentioned problem, the analytical method will be sought when the section of component and force bearing status are both simple.Based on analytical ideas of computing elastic-plastic buckling of member under the axial compressive loads and bending moments, the analytical expressions of calculating the ultimate load of buckling about neutral axis with maximum moments of inertia for the H-shaped, the square/rectangular hollow section steel member with/without flange outsides wrapped by the carbon fibre and circular steel tube without/with outsides wrapped by the carbon fibre are derived in this paper. Furthermore, the results of the finite element are provided.In the calculating, the two situations of buckling in the compression side and in the both compression and tension sides of the steel member with pinned-pinned ends is discussed. Furthermore, the situation of yield region varying in the flanges or webs is considered respectively for the H-shaped, the square/rectangular hollow section steel member. For the thinness wall of the circular steel tube, the change of the plastic region along the wall thickness is no longer considered.Subsequently the analytical expressions of calculating the ultimate load of buckling about neutral axis with maximum moments of inertia for the H-shaped steel member with the initial geometrical defects whose flange outsides wrapped by the carbon fibre, subjected the axial compressive loads and bending moments, are formulated. The reinforcing effect of the member with the initial geometric defects and the perfect member by the carbon fibre is investigated. Given the both ends the different bending moments, the comparison study of the ultimate load of the member wrapped by the carbon fibre with initial geometrical defects and perfect member is presented. It is difficult to get the analytical solution of stability problem with the effect of the initial residual stress. By using the finite element method to solve the buckling of the H-shaped steel member with the pined-pined ends and with the initial residual stress, the discipline of the bending moments change with the ultimate load is discussed. Specially, the reinforced effect of the composite material with the larger bending moments is presented.By giving some parameters such as the ultimate load and the thickness of the elastic core, the curves of the bending moments versus the ultimate loads for buckling of the H-shaped steel member with the different slenderness ratios are in good agreement with the results obtained by the steel structural design codes. Then, the corresponding relationship curves of the bending moments versus the ultimate loads for the H-shaped steel member wrapped by carbon fibre are presented, and practical simplified formula of the ultimate load is obtained. To prove the simplified formula accuracy and provide the reference for the engineering design, the relationship curves of the bending moments versus the ultimate loads for the H-shaped steel member wrapped by carbon fibre before and after with the different sections size are enumerated respectively.Under the different ends bending moments, the nonlinear dynamic buckling analysis of the H-shaped steel member reinforced by the carbon fibre before and after, subjected by impact load and cyclic load, is given. Then, the ultimate load of the member under impact load and the cyclic horizontal ultimate load under cyclic load are obtained respectively. Finally, the effects of the boundary condition, the thickness of the carbon fibre and the Elastic modulus on the H-shaped steel member under dynamic load is discussed.更多还原