【作者】 戴鹏；

【导师】 周绪红；

【作者基本信息】 长安大学 ， 桥梁与隧道工程， 2007， 博士

【摘要】 本文回顾了曲线预应力混凝土(Prestressed Concrete,PC)箱梁桥的理论研究现状和工程应用概况,在此基础上,针对相关病害特征和研究工作的不足,主要对曲线PC箱梁桥支座反力和极限承载力展开了研究工作。本文主要完成了以下几个方面的工作:(1)采用曲线PC箱梁室内模型,对支座设置及支座反力进行了参数试验研究。首次进行了预应力对支座反力影响的专项模型试验研究。根据试验结果总结了调整抗扭支座和中支座位置来改善支座反力分配的方法;总结了预应力作用对曲线PC箱梁产生的外扭转不利效应,得到了预应力引起的支座反力变化的基本规律。(2)采用室内试验模型,对曲线PC连续箱梁的承载力进行了试验研究。根据试验结果得到了对称竖向荷载作用下,试验模型的非线性力学特点和变形规律,总结了曲线PC箱梁的受力控制截面,混凝土裂缝的分布和发展以及整体结构的破坏形态,为这种结构的设计和应用提供了详实的试验资料和依据。(3)根据曲线PC箱梁的空间受力特点,确定了有效预应力的计算方法和参数取值,提出了预应力效应的模拟方式,采用基于实体单元的组合有限元法,提出了适合于曲线PC箱梁桥支座反力精细分析的数值模型。该模型能模拟预应力钢束实际线形以及曲线箱梁的构造细节,克服了杆系分析模型支座反力计算误差大的缺陷。与试验结果的比较表明:该数值方法具有直观、详实、精确、可靠的特点。通过对工程实例桥的分析总结了支座反力的分布规律。(4)根据曲线PC箱梁桥支座受力特点和相关病害,提出引入铅销橡胶支座隔震装置。对曲线PC箱梁桥隔震支座体系进行非线性动力时程分析,总结了曲线箱梁桥地震动的输入方式和地震响应特性,研究了铅销橡胶支座的减隔震效果和适用性。结果表明:将铅销橡胶支座与常用限位辅助设计结合应用,既可以减轻常见病害,同时避免了限位装置带来的不利影响,值得推广应用。(5)基于实体单元的组合非线性有限元法,研究了局部构件的模拟、网格的控制、钢筋与混凝土的分析模型以及混凝土材料非线性分析模型,提出了适合于曲线PC箱梁桥极限承载力精细分析的数值模型。通过采用多单元类型和细分网格,克服了混凝土结构非线性分析计算收敛困难的缺陷。该数值方法摒弃了简化分析关于结构应力和变形的假定,能计入箱梁的翘曲、畸变以及剪力滞等空间力学效应,可以清晰的描述混凝土裂缝的发生、发展、相互作用以及最后形成宏观压溃及破裂的整个过程。该数值方法算得的结构变形、应变及破坏形态与试验结果吻合良好,计算精度高,结果详实可靠。(6)依据验证后的分析方法,建立了理想的曲线PC连续箱梁精细数值模型,研究了中支座设置、曲率以及预应力等参数对承载力的影响。根据计算结果总结了相关因素对曲线PC箱梁桥承载变形、应变规律和破坏形态的影响。更多还原

【Abstract】 In the dissertation,it is reviewed the theoretical research and application of curved prestressed concrete(PC) box girder bridge.As the drawbacks of pertinent disease characteristics and current research,studies on bearing forces and ultimate bearing capacity of curved PC box girder bridge are carried out.The dissertation mainly completes the research in the following aspects:(1) Test model is employed for the first time to do parametric study of the bearings layout and bearing forces of curved PC box girder bridge.It is the first time to carry out test research of the prestressing forces’ influence on bearing forces.Based on the test result,the method to improve distribution of bearing forces by adjusting the location of torsion resistant bearing and middle bearing is concluded.Moreover,the adverse effect of prestressing forces to make curved PC box girder bridge turn outward is summarized.And the basic rule of bearing forces’ variation caused by prestressing forces is obtained.(2) Test study of ultimate bearing capacity of curved PC continuous box girder bridge is performed by using large scale model.According to test result,the nonlinearity characteristics and deformation rule of the model under symmetric vertical loads are found.As for the curved PC box girder bridge,critical sections,distribution and development of concrete cracks and failure mode of the whole structure are concluded,providing detailed test data as well as design and application basis of this structure.(3) The computation method and values of parameters for effective prestressing forces are determined by taking account of the spatial mechanical characteristics of curved PC box girder,and the way to simulate prestressing forces’ effect is proposed.Using assembled finite element method which mainly consisting of solid element,numerical model is come up with. This model is suitable for precise analysis of bearing forces of curved PC box girder bridge. The model can simulate actual alignment of tendons and structural details,suppressing the defect of bar element model which has large error in computing bearing forces.Compared with test result,the numeric method proposed in this dissertation is proved to be explicit, accurate and reliable.Additionally,the distribution rule of bearing forces is concluded through analysis of project example.(4) According to the mechanical characteristics and pertinent disease of curved PC box girder bridge,it is proposed to use the lead rubber bearing for seismic isolation.Nonlinear dynamic time history analysis is performed for seismic isolation bearing system of curved PC box girder bridge.The way to input seismic record and characteristics of seismic response of this type of bridge are summed up.The effectiveness of seismic isolation and its adaptability was studied.The result shows combination using of lead rubber bearing and seismic restrainers can not only eliminate the usual defects of curved PC box girder bridge,but can also avoid the negative effect that caused by seismic restrainers,so it is deserved to make popularized.(5) Simulation of local members,mesh control,tendon and concrete model,and materialistic nonlinear model of concrete are studied based on the assembled nonlinear finite element method(mainly composed of solid element).Then,numeric model for precise analysis of ultimate bearing capacity of curved PC box girder bridge is come up with. Through adopting multi-type elements and subdividing mesh finely,the convergence difficulty in nonlinear calculation for concrete structure is conquered.This numerical method gets rid of the assumption on stress and strain for simplifying analysis,and can take account of spatial mechanical effect such as torsion,distortion and shear lag of box girder,so the whole process from concrete cracks’ appearance,development and interactive effect to the macro crushing and collapse can be clearly described.The deformation,strain and failure mode got from this numerical method agree well with that from test.The comparison shows that this method is of high computation precision and the results are full,accurate and dependable.(6) On the basis of verified analytical method,an ideal precise numerical model of curved PC continuous box girder bridge is established.With the help of this model,the influence of the parameters such as layout of the middle bearing,curvature and prestress on ultimate bearing capacity are studied.According to the calculation results,the pertinent factors’ influences on load capacity,deformation,rule of strain and failure mode are summarized.更多还原