【作者】 刘睿；

【导师】 张敏； 周水兴；

【作者基本信息】 重庆交通大学 ， 结构工程， 2011， 硕士

【摘要】 随着山区高速公路和城市道路的不断建设,变截面桥墩和异型桥墩因其受力合理、节省材料等优点在现代桥梁工程中广泛应用。现行《公路钢筋混凝土及预应力混凝土桥涵设计规范》中仅给出等截面桥墩的计算长度系数,未给出计算变截面桥墩计算长度系数的通用公式。虽然可以采用有限元法较为精确地计算变截面墩的承载力,但计算要求高、适用性差,效率低。本文以假想固结点和换算惯性矩计算理论为基础,引入了传递矩阵法及能量原理中的瑞利-里兹法等算法,运用力学平衡原理,开展了以下研究工作:①计入桩基影响的墩身实际长度的研究。开展桥墩计算长度的理论计算,确定构件的实际长度是关键。为反映墩身受桩与地基土的影响,针对工程上常用的摩擦桩、端承桩和嵌岩桩,引入假想固结点计算原理,以桩顶水平位移和转角为控制量,运用m法计算受地基土影响的桩顶水平位移和转角与不考虑土层影响的假想固结点法计算的结果一致为目标,并且引入桩身材料系数作为假象固结点法的附加参数,开展假想固结点计算公式的推导。计入了地基土之间复杂的相互作用对墩身的稳定、承载力和抗推刚度的影响,重新界定了墩身构件实际长度的取值;②变截面桥墩等效于等截面桥墩的换算惯性矩的研究。墩身惯性矩是桥墩计算长度理论计算的重要参数。本文参考了稳定理论中计算长度的计算方法,将变截面墩等效为等截面墩,并使两者临界荷载相等为条件,引入用瑞利-里兹法和传递矩阵法分别对渐变截面和阶形变截面桥墩的换算惯性矩开展了公式的推导工作。并对变截面桥墩的换算惯性矩的计算公式进行合理简化,使其满足工程计算公式的简便性的特点,同时提高其计算精度,扩大了公式适用范围;③墩顶约束刚度计算公式的推导。墩顶约束是影响构件计算长度计算精度的重要条件。结合本文推导的假想固结点和换算惯性矩公式,将变截面桥墩等效成欧拉柱对墩顶约束刚度的中间参数——墩顶抗推刚度的计算公式进行简化。并通过实际工程数据对抗推刚度公式的计算结果进行验证。④结合以上研究的内容,借鉴结构稳定理论中求解欧拉柱计算长度系数的微分方程针对变截面墩的计算长度系数进行计算,并针对相关实体工程项目用ANSYS建立有限元模型,所有公式的计算结果进行验证。更多还原

【Abstract】 With the development of highway in mountainous area and city road, variable cross-section Pier is widely applied in the modern bridge engineering for its reasonable mechanical property and low cost in material. The coefficient of effective length of the uniform cross section pier is proposed referring to the standard of“Code for Design of Highway Reinforced Concrete and Prestressed Concrete Bridges and Culverts”. But the general formula of coefficient of effective length of the variable cross-section Pier is not put forward in this standard. The bearing capacity of variable cross-section Pier can be calculated exactly by the method of FEM, which is lack of applicability and efficiency. Basing on the theories of virtual rigid joint and conversion inertia moment, mechanical balanced principle is applied in this paper to research the following works by energy method and transfer-matrix method.①The length of pier body considering the influence of pile foundation is investigated. It is important to calculate the effective length of pier and ensure the length of the component. The pier body is effected by pile and foundation soil. According to the point bearing pile, friction pile and driven pile, virtual rigid joint method is proposed. M-method is used to calculate the horizontal displacement and rotation on the top pile.②The conversion inertia moment of the uniform cross section pier which is equivalent to the variable cross-section Pier is investigated. The inertia moment of pier shaft is the important parameter in the calculation of effective length. The variable cross-section pier is equivalent to the uniform cross section pier in the condition of the same critical load referring to the method of effective length upon stability theory. The formula of conversion inertia moment of variable cross-section is deduced and simplified by Rayleigh-Ritz method and transfer-matrix method to improve its applicability and precision.③The formula of constraint stiffness of the top pile is investigated. The precision of effective length is effected by the constraints of top pile. According to the formula of virtual rigid joint and conversion inertia moment, the formula of anti-pushing rigidity is simplified through equivalent Euler column. The solution of the formula of anti-pushing rigidity is proved comparing with the data of real engineering. ④Combining the investigated content, the coefficient of effective length of the variable cross-section pier is calculated by the differential equation of Euler column in stability theory .Solid model established by the general FEM software of ANSYS is calculated and compared with all the solution of formula.更多还原