【作者】 李开言；

【导师】 陈政清；

【作者基本信息】 中南大学 ， 桥梁与隧道工程， 2005， 博士

【摘要】 作为一种无支架施工方法,平衡悬臂施工法在连续梁桥、连续刚构桥、斜拉桥施工中得到了普遍的采用。双肢薄壁高墩连续刚构桥因经济上的竞争力和施工上的方便性,在国内得到了较多的采用。但这种结构在平衡悬臂施工阶段存在一些问题,本文研究主要集中于施工阶段稳定性分析和风效应研究: 1) 以稳定性分析为目标,基于弹性力学基本方程和变分原理,推导了单层、多层门式刚架的临界荷载表达式和带双横联的双肢薄壁墩平衡悬臂施工阶段稳定性系数计算的简化计算公式,该计算式简单明了、方便使用。以贵阳小关桥3号桥墩平衡悬臂施工多个阶段的稳定性计算为例,比较了本文算法和有限元分析结果,计算结果偏差小说明了本文方法的可靠性和工程适用性。 2) 以双肢薄壁高墩连续刚构桥平衡悬臂施工的简化计算模型出发,运用拉格朗日方程推导了其运动方程并获得了其自由振动频率,对特征方程的处理使得该方法可用于单横联双肢薄壁墩刚构桥、单薄壁墩刚构桥,具有较好的工程适用性。以贵阳小关桥为例,通过有限元分析、现场动力试验和本文结果对比,验证了本方法在计算双肢薄壁高墩刚构桥平衡悬臂施工阶段动力特性上的可靠性。该法只需计算器运算而无需有限元专用程序计算,简单方便,适合于工程单位使用。 3) 完成了小关桥3号墩双肢薄壁刚构平衡悬臂施工多个工况的现场动力试验,模态分析的现场试验结果与有限元分析、本文动力特性快速算法结果的一致性好。研究思路形成了以现场动力试验结果为依据,以模型修正技术为手段,通过修正简化动力模型,由稳定性快速算法及时判断施工结构稳定安全性的方法。 4) 采用CFD方法模拟了连续刚构桥双肢薄壁高墩在纵桥向和横桥向风作用下的风载特性。针对工程实际范围内的单肢截面长宽比和双薄壁间净距变化,分别研究了纵桥向风作用下这些参数变化对上下游薄壁阻力系数的影响,以及横桥向风作用下当这些参数变化时薄壁顺风向风力系数和横风向风力系数的变化。借助数值风洞结果,研究了小关桥平衡悬臂施工最大悬臂阶段的驰振稳定性。 5) 采用既考虑脉动风又考虑了结构尾流中的漩涡脱落引起的脉动风荷载的三维风荷载模型。提出了利用有限元分析法获得双肢薄壁高墩内力的影响函数,并以此计算由平均风荷载响应和背景响应所产生的墩底内力方法。提出了利用主要模态计算墩底内力的共振响应部分,利用峰值因子建立背景响应、共振响应与最大响应之间关系的方法,以此获得双肢薄壁墩墩底内力的最大响应。以小关桥平衡悬臂施工最大悬臂为例研究了三维风荷载作用下的墩底内力响应,计算结果显示了充分考虑风荷载的三维效应的必要性。更多还原

【Abstract】 Balanced cantilever erection for continuous girder bridges, continuous rigid frame bridges（CRFB） and cable-stayed bridges has been recognized as one of the most efficient methods of building bridges without the needs for falsework. Because of its economy and convenience for construction, the CRFB with high flexible twin piers（HFTP） are commonly built in China. While several problems exist in cantilever construction stage, this paper focus the studies mainly on stability and wind effects.1) The critical loads of single-floor, multi-floor rigid frame were deduced, and simplified formula of stability coefficient relative to the HFTP with two horizontal connecters during cantilever erection were also obtained. This simple formula is of convenient, and can be used to analysis the stability of different cantilever construction stage of the XiaoGuan Bridge, the efficiency and validity were confirmed after comparing the results to that of from FEM.2) The moving equation of the structural model, which was simplified from the balanced cantilever structure of the CRFB with the HFTP, was deduced by using the Lagrange Equation. Accordingly, the free vibration frequency could be obtained. This method was employed to obtain the dynamic characteristic of the XiaoGuan Bridge. It was found that the results of the presented method were in better consistence to that of from FEM and field tests. This simple and fast algorithm could be used without help of FEM program, which is suitable for bridge construction.3) Ambient vibration tests were carried out on 3^nd pier of the XiaoGuan Bridge during the balanced cantilever erection, the results from the field mode tests were compared with that of FEM and that of the present algorithm, good agreements were found. So, a new fast approach connecting the construction stability, model updating technology and field mode test was presented to duly evaluate the structure stability.4) The CFD method was applied to study the Wind loads on HFTP of CRFB, both in longitudinal and lateral directions. The effects on aerodynamic drag coefficient subject to change of geometrical parameters in HFTP were studied. Based on aerodynamic coefficients from CFD, the galloping stability of the XiaoGuan Bridge during the maximum cantilever stage was also studied.5) A wind load model of CRFB with HFTP at erection stages was employed taking into account all wind effects on girder and piers. The influence function was presented which could be attained by the FEM. The wind effects on inner forces at bottom of piers were decomposed into different parts that could be acquired from different way. The peak maximum was obtained by using the gust factor to set up the relation between the buffeting effect and the peak maximum. Finally, the application was illustrated with reference to the XiaoGuan Bridge. It was shown that taking all the roles of different loading components into consideration is very important.更多还原